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12: Theory of Evolution - Biology


12: Theory of Evolution

Welcome to the Living World

Evolution is an orderly change from one form to another.

Evolutionary Biology is the study of evolutionary history of life forms.

- Big Bang Theory states that universe originated about 20 billion years ago by a singular huge explosion .

- The earth was formed about 4.5 billion years ago.

- There was no atmosphere on early earth. Water vapour, CH4, CO2 & NH3 released from molten mass covered the surface.

- The UV rays from the sun broke up water into H2 and O2.

- Oxygen combined with NH3 & CH4 to form water, CO2 etc.

- The ozone layer was formed. As it cooled, the water vapour fell as rain to form oceans.

- Life appeared almost four billion years ago.

THEORIES OF ORIGIN OF LIFE

1. Theory of spontaneous generation (Abiogenesis): It states that, life came out of decaying and rotting matter like straw, mud etc.

Louis Pasteur disproved this theory. He demonstrated that life comes only from pre-existing life.

He showed that life did not come from killed yeast in a closed pre-sterilized flask. But in an opened flask, life (microbes) appeared.

2. Biogenesis: Proposed by Francisco Redi, Spallanzani & Louis Pasteur. It states that, life originates from pre-existing life. But it does not explain origin of first life.

3. Cosmic theory (Theory of Panspermia): It states that, the units of life (spores) were transferred to different planets including earth.

4. Theory of special creation: It states that, living things were created by some supernatural power (God).

5. Theory of chemical evolution: Proposed by Oparin & Haldane. It states that, the first form of life was originated from non-living inorganic & organic molecules such as CH4, NH3, H2O, sugars, proteins, nucleic acids etc. i.e. “Abiogenesis first, but biogenesis ever since”.

Urey-Miller experiment

- Harold Urey & Stanley Miller experimentally proved theory of chemical evolution. They created a condition like that of primitive earth (i.e. high temperature, volcanic storms, reducing atmosphere with CH4, NH3, H2O, H2 etc).

- They made electric discharge in a closed flask containing CH4, NH3, H2 and water vapour at 800 o C. As a result, some amino acids are formed.

- In similar experiments, others observed formation of sugars, nitrogen bases, pigment and fats.

First non-cellular forms of life originated 3 billion years ago. They were self-replicating metabolic capsule containing RNA, proteins, Polysaccharides etc.


Origin of Life: 4 Theories | Evolutionary Biology

Life on earth appeared 500 million years after its formation. Different theories were given by different thinkers and scientists.

(i) Theory of Special Creation:

It states that God created life by his divine act off creation, i.e., the earth light plants and animals are all being created by the supernatural power.

This theory has following connotations:

(a) All living organisms (species or their types) that we see today were created as such.

(b) Diversity of life form will not change in future.

(ii) Theory of Panspermia or Cosmozoic Theory:

It was given by early Greek thinkers, which states that the spores or panspermia came from outer space and developed into living forms.

(iii) Theory of Spontaneous Generation:

It states that life originated from decaying and rotting matter like straw, mud, etc. Louis Pasteur rejected the theory of spontaneous generation and demonstrated that life came from pre-existing life. In his experiment, he kept killed yeast cells in pre-sterilised flask and another flask open into air. The life did not evolved in the former but new living thing evolved in the later flask.


Evolution is the Fuel Behind Racism

The riots that have plagued the world during the last few weeks were, in my experience, the worst I have seen in my lifetime. Even those that occurred after Martin Luther King, Jr., was murdered were not as violent. I was born and reared in Detroit and remember the race riots, fires and looting on 12 th Street, not far from where I spent nine years at Wayne State University for my Bachelor’s, Master’s and Doctorate degrees. One description follows:

Scorching images from across the country fill our screens, a reminder that the racial past remains an unhealed burn in America’s present. …. It is getting very close to home. Some have called racism America’s historical “original sin.” Where did many white people of the past get the wicked idea that their lives matter more than black lives? The question is complex but, without doubt, Darwinian theory helped to fuel our present racial fire. [1]

The close connection between racism and evolution will not surprise historians of evolution. The reason is, because the main proof of human evolution for a century after Darwin published his book that changed the world was the ‘evidence’ from ‘inferior races.’ One of the best examples are the many drawings of various races which were ranked from the highest most-evolved humans, to the lowest, the less-evolved humans. The least-evolved humans shown were very similar to the highest-evolved apes. As Klinghoffer writes, Charles Darwin conceived the idea of evolution which

posits a racial hierarchy. That’s not surprising, since the theory sees all of life as a vast smudge, graduating from the simplest to the most complex animal life. In any hierarchy, someone has to be at the bottom. As Darwin stated explicitly in The Descent of Man, that place was occupied by Africans. For generations, American public school children learned from their biology textbooks the pseudoscience that Caucasians are more “advanced” on the evolutionary ladder than Africans. Yet this was the scientific consensus of its day. [2]

Eugenics turned out to be one of the worst blights on humanity that eventually lead to the Nazi holocaust which, in turn, resulted in the murder of over 12 million lives.

Figure 1. Illustrations in Chapman [13] Using Race Hierarchies to Prove Human Evolution. Number 13, the Papuan is the lowest human race, the Hottentot is number 14 both are close to the Gorilla (number 12). Note that the Gorilla and the Hottentot are almost identical. A Negro is number 16 and a European, the highest race, is number 24. The Gorilla profile was greatly distorted to look human and the Papuan and Hottentot greatly distorted to look like apes. This distortion is called “artistic license.” Below is the caption to the illustrations.

NATIVE COUNTRY.
1. Baboon Guinea
2. Pig-faced Baboon Cape Land
3. Macaque Sumatra
4. Semnopitecus Java
5. Nasalis Borneo
6. Gibbon India
7. Orang, young (female) Borneo
8. Orang old Guinea
9. Chimpanzee, young (female) Guinea
10. Chimpanzee, old Guinea
11. Gorilla, young (female) Guinea
12. Gorilla, old Guinea
13. Papuan (female) Van Diemen’s Land
14. Hottentot Cape Land
15. Caffre Zulu Coast
16. Negro Soudan
17. Australian Victoria Land
18. Malay (female) Polynesia
19. Mongolian (male) Thibet
20. Arctic (female) Kamtchatka
21. American (male) Mississippi
22. Drave India
23. Nubain Kordofan
24. European Greece


Very Low in the Human Scale

As Klinghoffer writes, the harm of this racist past has resulted in many evils including

Dehumanizing Africans and others is not only part of America’s, but of evolutionary biology’s terrible burden. Near the turn of the last century, in New York City, St. Louis, Seattle, and elsewhere, Africans and other native people were put on exhibit in zoos, as animals. Human Zoos recounts, among other heart-breaking stories, the life of African pygmy Ota Benga (1883-1916). He was bought in a slave auction and displayed in 1906 alongside an orangutan in the Monkey House at the Bronx Zoo. The organizers intended this as a lesson for the public, illustrating the scientific truths of Darwinian theory. African-American clergy at the time spoke out against the insult to their dignity, only to be dismissed by the New York Times, which explained that “the pygmies … are very low in [on] the human scale.” [14]

Present-day racists and others continue to draw on Darwinian racial theory. Protesters called for racial justice, remembering George Floyd and his death at the hand of four Minneapolis policemen, two of which were themselves persons of color. But how many remember the horrific injustice that occurred, in the name of science, just a few miles away? Namely, African American Ota Benga’s protest — “I am a man! I am a man!” — summarizes the very best message of the struggle for human rights today. [15]

Figure 2. Notice how the ape-man, so-called missing link, is drawn very negroid in appearance, more so than even the distorted drawing of a chimp, which was drawn in profile to show the similarity. From the Illustrated London News, 14 February 1925, p. 5. This drawing is by the very talented French artist, Amédée Forestier.

Evolution of Homo erectus Racial Attitudes

In the 1920s, only Piltdown Man, Java and Peking Man, and some Neanderthal bones existed as evidence of human evolution from some ape-like creature, and these were very human, not at all ape-like. Then, when more fossils were uncovered, Peking Man was found to be “very similar to [the] Pithecanthropus erectus fossil that Eugene Dubois had found in Java.” [3]

Furthermore, “anthropologists had only the work of Dutch anatomist Eugene Dubois on which to base theories of the presence of early man in Asia,” the location then widely thought to be the evolutionary origin of mankind, according to Darwin’s writings. [4] In short, only Java-Peking Man and Piltdown Man existed, plus a large collection of very human Neanderthal bones. [5] Piltdown was proven to be a fraud only in 1953. Peking Man and Java Man are now both classified as Homo erectus, regarded as a putative primitive race of humans, but not evidence of a significant progression of evolution from monkeys.

Thus, at best, Java Man, Peking Man and Neanderthal Man, were all clearly humans but judged as inferior variations. As they were then the only evidence for evolution, they all were pictured in illustrations as Negroes. It was only in the 1960s that other fossils were discovered which were regarded as non-humans evolving into humans, namely the australopithecines, by the Leakeys. Their July 1959 find was first called Zinjanthropus boisei, now called Australopithecus boisei. For this reason, the best evidence then for evolution until the 1960s was the living “inferior” races, and evolutionists exploited this evidence to the hilt. An example is the book used in the Scopes Monkey Trial. At issue in the trial were certain chapters on evolution and eugenics in a biology text by George W. Hunter titled A Civic Biology that was mandated by the state of Tennessee and many other states. [6]

Impact of Evolutionary Racism on the Scopes Trial

For nearly a decade, Hunter’s book was the most widely used high school science textbook in the nation. The textbook was endorsed by many distinguished professors, including those at elite Universities including Brown and Columbia. [7] Tennessee parents and teachers had no problem with the bulk of the text, which covered Earth’s plants and animals, but were concerned mostly about its teaching of human evolution. Then, in March of 1925, the Tennessee legislature passed a law that made it illegal in public schools “to teach any theory that denies the story of the Divine Creation of man as taught in the Bible, and to teach instead that man has descended from a lower order of animals.” [8]

A major concern of attorney William Jennings Bryan was the racism and degradation of humans by evolution and the influence of evolution on racism. From the many drawings, a few of which are reprinted here, the racist images are obvious. They bothered a man such as Bryan, who believed that all men descended from Adam and Eve, thus all are equal. The Hunter text illustrated Bryan’s concern because it was “laced with the racism of the day.” [9] Its discussions of eugenics included such scarlet passages as the following openly racist claim that claimed currently “there exist upon the earth five races or varieties of man, each very different from the other … the highest type of all, the Caucasians, [is] represented by the civilized white inhabitants of Europe and America. [10]

Hunter also wrote that, as we can improve domesticated animals by breeding, likewise the “future generations of men and women on the earth” can also “be improved by applying to them the laws of selection.” This process is called eugenics. Hunter stressed that eugenics is no small concern because nothing less than the “improvement of the future race” was at stake. [11] Hunter, under the subheading “Eugenics,” then made it clear what type of “improvement” programs he was referring to:

When people marry there are certain things that the individual as well as the race should demand. The most important of these is freedom from germ diseases which might be handed down to the offspring. Tuberculosis … and feeble-mindedness are handicaps which it is not only unfair but criminal to hand down to posterity. The science of being well born is called eugenics. [12]

Another example is Rhodesian Man (Homo rhodesiensis) the species name proposed by Arthur Smith Woodward.

Figure 3: The skull named Rhodesian Man was discovered in 1921 and claimed to be a missing link of our less-evolved evolutionary ancestors. Public domain.

Note how the artist gave the figures prominent eyebrow ridges, the projecting upper lip, the large eye-sockets. The squatting figure is crushing seeds with a stone, and a rock used for crushing is lying on the rock to his right. The figure in the foreground is holding a staff. On the left, behind the sitting figure, is the entrance to their cave. This Rhodesian Man cave dweller was, when this picture was drawn, regarded as an extinct intermediate between Neanderthal Man and Modern Man. [16]

Figure 4. Peking Man discovered in China. Notice the attempt to tailor this image to the stereotypical Oriental. Also note the main difference between most modern men and the supposed missing link is the prominent prognathous jaw. From Wikimedia Commons.

A Forgotten Legacy? No Longer.

The 2020 demonstrations in our nation have been a lesson on how science intersects with culture. The documentary Human Zoos: America’s Forgotten History of Scientific Racism, directed by Discovery Institute Vice President John West, is a good summary of this history. The 19th- and 20th-century racists might have instructed us to “Listen to the scientists.” In the multiple award-winning Human Zoos, Dr. West unearths the story. Many listened to the scientists and some of the problems we see today have resulted. Human Zoos reminds us that this history must not be forgotten. What is going in our country can’t be grasped without understanding this history. So far close to a million viewers saw it on YouTube.

[3] Reader, John. 1981. Missing Links: The Hunt for Earliest Man. Chapter 4: Peking Man, p. 114. Boston, MA: Little Brown & Company.

[4] Janus, Christopher, with Brashler, William. 1975. The Search for Peking Man. New York, NY: Macmillan Publishers, p. 20.

[5] Hood, Dora. 1964. Davidson Black: A Biography. Toronto, Canada: University of Toronto Press, pp. 29, 35.

[6] Hunter, George. 1914. A Civic Biology. New York, NY: American Book Company.

[7] Larson, Edward John. 1997. Summer for the Gods: The Scopes Trial and America’s Continuing Debate over Science and Religion. New York, NY: Basic Books.

[8] Ginger, Ray. 1958. Six Days or Forever?: Tennessee versus John Thomas Scopes. New York, NY: Oxford University Press, p. 3.

[13] Chapman, Henry. 1873. Evolution of Life. Philadelphia, PA: J. B. Lippincott. The illustrations are in the appendix. From 1877 to 1880 Chapman was demonstrator of physiology at the Jefferson Medical College, and 1879–1880 was curator of the museum. In 1878 the college awarded him his second degree in medicine for a thesis on the “Persistence of Forces in Biology.”

[16] Woodward, Arthur Smith. 1921. A New Cave Man from Rhodesia, South Africa. Nature. 2716(108): 371-372, November 17.

/>Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,300 publications in 12 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,500 college libraries in 27 countries. So far over 80,000 copies of the 40 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.


Evolution - Class 12, Biology | EduRev Notes

ORIGIN OF LIFE

Big-Bang Theory :

Proposed by Abbe Lemaitre.

According to it, the universe originated about 20 billion years ago due to a thermonuclear explosion.

This thermonuclear explosion is called Big-bang.

Flat-disc like structure is called SOLAR-NEBULA formed.

About 4.5 billion years ago, the origin of our solar system took.

The very hot central part of this solar Nebula became still hotter & converted into the sun. Now, due to condensation of atoms & dust particles moving around the sun, formation of the other planets took place [Mercury, venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune].

The solid part of our planet earth was called Lithosphere & the gaseous part was known as atmosphere.

When the earth's surface cooled down and its temperature decreased to 100°C, water formed on it.    

Ancient Theories for origin of life :       

1.   Theory of special creation  –

The greatest supporter of this theory was father Suarez According to Bible life and everything was created by god in 6 days.  

on first day     : Earth and heaven

on second day : Sky and water   

on third day    : Land and plants

on fifth day     : Fishes and birds

on sixth day    : Land animals and first man Adam and from his 12 th Rib first woman Eve.

According to hindu mythology the world was created by God Brahma. (The first man was Manu and the first woman was Shraddha)

According to it life has not changed ever since its origin.

Special creation theory lacks scientific evidences so is not accepted.

2.  Theory of Spontaneous Generation (Abiogenesis or Autogenesis) –

This hypothesis was supported by ancient Greek philosophers like Thales, Anaximander, Xenophanes, Plato. Empedocles, Aristotle.

According to this theory life was originated from nonliving things spontaneously.

They believed that the mud of the Nile river could give rise to frogs, snakes, crocodiles.

Abiogenesis was strongly supported by Von Helmont. He claimed formation of mice in 21 days. If a sweat soaked dirty shirt is kept in wheat barn.

3.   Cosmozoic Theory –

Proposed by Richter.

Protoplasm reached on earth in the form of spores or other simple particles from some unknown part of the universe with cosmic dust and they gave rise to various forms of life. 

4.   Cosmic panspermia theory –

Proposed by Arrhenius.

According to this theory organisms existed throughout the universe and their spores could freely travel through space from one star to the other.

5.   Theory of Eternity of Life –

Helmholz believed that life is immortal.

6.  Theory of Biogenesis –

Harvey (1651) and

Huxley (1870)

New organisms can be originated on earth only by pre-existing life.

This theory rejected the theory of Spontaneous generation but cannot explain origin of life.

To prove Biogenesis and to disprove abiogenesis experiments were performed by  –

Francesco Redi (Italian 1668) –

He took cooked meat in three jars, one was uncovered, the second was covered with parchment and the third was air tight.

He observed that maggots developed only in the uncovered jar while maggots could not develop in the meat in closed jars.

This proved that larvae were formed from eggs laid by the flies in open jars. Since the meat in closed jars could not be visited by flies so no larvae could develop. Therefore life originated from pre existing life.

Lazzaro Spallanzani (Italian 1767)  –

He boiled vegetables and meat to prepare a sterlized nutritive soup and he kept some of it in air sealed flasks and some in loosely corked flasks.

He observed that the soup in sealed flask remained sterile while micro organisms appeared in the soup in loosely corked flasks.

Thus even micro organisms were formed from pre existing ones in the air rather then spontaneously.

Louis Pasteur (French 1862) –

Pasteur is popular for Germ Theory of Diseases or Germ theory and he disproved abiogenesis.

He prepared sterlized syrup of sugar and yeast by boiling them in flasks.

He took two flasks one of broken neck and another of curved neck (swan neck flask). No life appeared in swan neck flask because germ laden dust particles in the air were trapped by the curved neck which serves as filter while in broken neck flask colonies of microorganism were developed.

Modern theory of origin of life :

(Oparin-Haldane theory of origin of life)

Naturalistic theory Or Theory of Chemical Evolution –

This theory was proposed by Russian Scientist A.I. Oparin and J.B.S Haldane (England born Indian scientist)

Important Points

–  According to this theory life originated by the composition of chemicals. (Chemical evolution).

–  Oparin's theory is based on Artificial Synthesis. So also called as artificial synthetic theory.

–  I st life originated in the water of oceans. So water is essential for origin of life.

     There is no life on moon due to absence of water.

–   At the time of origin of life free O2 was absent, so first life was anaerobic.

–   In the primitive atmosphere free oxygen was present but complete oxygen consumed in composition so
primitive atmosphere of earth was reducing.

–   Oxygen was reproduced by photosynthesis and atmosphere converted in oxydising.         

Chemical Evolution :

1.   The atomic stage –

The earth was originated about 4.5 billion years ago. Early earth had free atoms of all elements which are essential for the formation of protoplasm.

The lightest atoms like carbon, hydrogen, nitrogen and oxygen formed the primitive atmosphere.

 

2.   Molecular stage (Origin of molecules and simple Inorganic compounds) –

Free atoms combined to form molecules and simple inorganic compounds.

Due to presence of high temperature, active hydrogen atoms combined with all oxygen atoms to form water and leaving no free oxygen.        

Thus the primitive atmosphere was reducing (without free oxygen) unlike present oxidising atmosphere (with free oxygen).

Hydrogen atoms also combined with nitrogen to from NH3.

(The first molecular compounds formed were probably water and Ammonia).

These Lighter elements also formed CO2 ,  CO, N2 , H2 etc.

3.   Origin of early organic compounds – 

The nitrogen and carbon of the atmosphere combined with metallic atoms forming nitrides and carbides.
Water  vapour and metallic carbides reacted to form to first organic compound Methane (CH4). Later on
hydrogen cyanide (HCN) was formed .

Water which formed on earth due to high temperature evaporated so clouds were formed.

Water vapour changed into rain drops and by the collection of water on earth primitive oceans were formed.

4.   Origin of simple organic compounds –

Water of primitive oceans contained large amount methane, ammonia, hydrogen, cyanides, carbides, nitrides.

These early compounds interacted and formed simple organic compounds like, aldehyde, Ketones. Alcohols
Pentose and hexose sugar, Amino Acids, Glycerol, Fatty Acids, Purines, Pyrimidines etc.   

Energy was obtained from  U.V. Rays of sunlight, cosmic rays and heat of volcanic eruptions.

5.   Origin of complex organic compounds –

The small simple organic molecules combined to form large complex organic molecules, e.g –

–    Amino acids Joined to form polypeptides and proteins, which were non-enzymatic.

–    Simple sugar units combined to form polysaccharides.

–    Fatty acids and glycerols united to form fats and lipids.

–    Sugar, nitrogenous bases, phosphates combined into nucleotides which polymerized into nucleic acid,

These macromolecules forms main component of protoplasm hence the possibility of origin of life in primitive oceans could be established.

After long time the water of primitive oceans became rich mixture of organic compounds as a result of

Haldane called this saturated water of oceans as prebiotic soup or hot dilute soup.

The major requirement for promoting polymerization is the availability of continuous source of energy and removal of water from the surface of reactants so that they can concentrate and prevent depolymerisation.

Experimental evidence for formation of simple organic compounds –

By Stanley Miller who was a student of Harold Urey.  

In this experiment Miller took the mixture of methane, ammonia and hydrogen (ratio 2 : 1 : 2) in a large flask and passed steam over it by boiling  water and connecting it with a glass tube.

Electric spark discharged in the mixture by using two tungsten electrodes as source of energy.

After 18 days this fluid was collected and analysed. This dark red fluid was found to contain.

–    Simple amino acids – glycine, alanine, aspartic acid.

–    Simple organic acids – formic, acetic, oxalic, lactic, succinic acids.


BIOLOGICAL EVOLUTION :

(i) Origin of  Protobionts and Nucleoprotein (Coacervates)

Macromolecules which were synthesized abiotically in primitive ocean later came together and formed large colloidal drop like structures named as Protobionts (Later called coacervates by oparin, Fox and called them Microsphere and Deamer called them vesicles).

Each protobiont was cluster of macromolecule.

They contain proteins, nucleic acids, lipids, polysaccharides etc.

They grew by absorbing molecules from their environment.

They could divide by budding like bacteria, many chemical reactions including the decomposition of glucose took place inside the protobionts.

The sun provide energy for chemical reaction.

According to oparin coacervates were the first sole living molecules which gave rise to cell. 

(ii) Origin of protocells [Eobiont :

The first living form named protocell originated in the primitive oceans.

The protocell were clusters of nucleo-proteins which formed by composition of nucleic acids and

Nucleoproteins had the property of self duplication.

Nucleoproteins were first sign of life.

The protocell represented the beginning of life.

From protocells or eobionts few core of nucleoproteins gets separated free in oceans and became inactive but when they enter in another eobionts they became active so virus like structures were formed.

Origin of virus like structure is an example retrogressive evolution (complex to simple).

1. Khorana (1970)artificially synthesized 77 nucleotide RNA molecule out side a living cell which suggests that probably RNA was the primordial genetic material rather than DNA.

Zaug, Thomas cech and Altman described that some RNA molecules have enzymatic activity hence probably the RNA enzymes called ribozymes were able to replicate the primordial RNA.

The discovery of RNA molecule working as enzyme has also changed our thinking about origin  of  life.

It is now believed that about 4 billion years ago earth was an 'RNA world' in which RNA molecule carried out all the process of life without the help of either protein or DNA,

By this discovery evolution is named as RNA world.

2. It is estimated that life originated about 3.0 billion years ago as protocell (eobionts) in precrambian era which was anaerobic heterotrophic.

(iii) Origin of Prokaryotes –

As a result of mutation the protocells became more complex and efficient and used the materials available in the surrounding medium and condensed themselves into prokaryotic cells.

Thus the first living being were prokaryotic, like bacteria they were single celled and consisted of naked DNA. Nutritionally they were chemoheterotrophs (saprotrophs), respiration was anaerobic.

(iv) Origin of Autotrophism –

It includes the origin of chemosynthesis and photosynthesis.

(a) Origin of chemosynthesis :

Due to continue withdrawal of organic molecules by chemoheterotrophs organic material decreased in oceans.

Before the organic material disappeared in sea, new modes of Nutrition developed, one of them was

chemosynthesis.

The organism which perform chemosynthesis are called as chemoautotrophs. They were anaerobic and synthesise organic molecules from inorganic material. The energy was obtained by oxidizing inorganic materials present in the sea.

Such mode of nutrition is found in Bacteria e.g. sulphur bacteria, nitrifying bacteria.

(b) Origin of Photosynthesis :

After some time bacteriochlrophyll developed in some autotrophic bacteria like organism.

They could absorb solar energy and convert it into chemical form these organism called photoautotrophs.
They utilize solar energy in synthesizing organic compounds. The process is called photosynthesis.

They were anaerobic and utilized hydrogen from sources other than water like H2S.

Therefore, no oxygen was evolved and atmosphere remained reducing .

This stage of photosynthetic autotrophism is represented by planktonic sulphur bacteria of today.

Oxygen revolution –

Liberation of free O2 by blue green algae like prokaryotes due to photosynthesis was a revolutionary change in the history of earth. It is called oxygen revolution.

It includes important changes like –

(1)  Atmosphere of earth changed from reducing to oxidising, hence possibilities of further chemical
evolution and abiogenesis got over, because chemical evolution always take place in reducing environment.

Origin of Eukaryotic cell –

About 2.7 billion years ago conditions become suitable for aerobic respiration with the release of free O2 . Aerobic respiration yields about 20 times more energy then anaerobic respiration hence the prokaryotes adapted themselves for aerobic mode of respiration.

Nucleus, mitochondria and other cell organelles developed in the cell and free living eukaryotic cell like organism originated about 2.0 billion years ago in the primitive ocean.

Organic Evolution –

1. Though life originated by chemical evolution on primitive earth, was later replaced by organic evolution.

2. Organic evolution states ''Descent with modification''. i.e. the present day complex organism have evolved from earlier simpler organism by small but gradual changes which have occurred over millions of years.

3. Though living organisms show diversity in size, structure, function, behaviour etc. they also show basically similar metabolic processes indicating common ancestory. 

Points to remember :

1.   Evolution up to formation of coacervates termed as chemical evolution, in which complex organic compound were formed which were essential for formation of cellular structure.

2.   Evolution from coacervates to simple cell structure known as biological evolution.

3.   From simple cell to recent…..evolution is called organic evolution, in which organism developed structures and modified them by which they became more adaptive in their changing environment.  

4.   First protein which is formed during evolution in primitive oceans were not structural.

5.   First nucleic acid which was formed in primitive oceans from combination of nucleotides, did not have power of replication. They obtained power of replication later by mutation.

6.   Evolution term introduced by - Herbert Spencer. 

      

 

7.   What is evolution ?

The word evolution  means to unfold or unroll or to reveal hidden potentialities. Evolution simple means an       orderly change from one condition to another.

8.   Evolution is a slow but continuous process which never stop-Buffon.

9.   Dollo's low – it states that evolution is irreversible.

10. Accroding to Theodosius Dobzhansky (1973), nothing in biology makes sense except in the light of
      evolution.

11. Scala nature or ladder of nature : –

Aristotle represented the evolution of complex organism from simple organism in the form of a ladder which is called Scala Nature or Ladder of nature.

He kept simple organism at the bottom of ladder and complex organism at the top of this ladder.

George cuvier studied the evolutionary history of organism by studying fossils and rejected Scala nature.

12. The history of life actually comprises two events :

(ii)  Evolution of life [the mechanism involved in the changes of living organisms through time]  

13. Two great themes of evolutionary biology :

(i) The diversity of life, including both the differences and similarities.

(ii) The characteristics of   organism, both adaptive and non-adaptive.

14. For origin of life, at least three conditions needed to have been fulfilled.

(i)   There must have been a supply of replicators i.e. self producing molecules.

(ii)  Copying of these replicators must have been subject to error via mutation.

(iii) The system of replicators must have required a perpetual supply of free energy and partial isolation from
the general environment.

15. Cosmology–Study of universe.

16. Biological evolution is also known as biogeny.

17. Unit of evolution is population.

18. Oparin's theory also known as primary abiogenesis.

19. Evolutionary biology-Study of history of life forms on earth.     

EVIDENCES OF ORGANIC EVOLUTION

Some important evidences are –

1.   Palaeontological Evidences –

Founder of modern palaeontlogy   :           George cuvier

Birbal Sahni is famous for Indian palaeonotology

Two branches of palaentology –

1.   Palaeobotany : Study of plant fossils

2.   Palaeozoology : Study of Animals fossils

Definition of Fossils was given by Charls Lyell ''Impression of past found in Rocks called fossils''

fossils provide one of the most acceptable evidence in support of organic evolution.

Type of Fossils :

1.   Unaltered Fossils :

In this type whole bodies of extinct organisms are found frozen in ice at the polar regions eg. Wooly
mammoths (25000 yrs before extinct fossils were found from Siberian region)

2.   Petrified fossils – Most common type of fossil.

Replacement of organic part by mineral deposits is called petrification.

These fossils consists of only the hard parts e.g. bones, teeth, shells, wood etc. of extinct organisms.

In human body first fossilization occurs of teeth.

3.   Mould fossils –

Here no part of the original organism is present, only an impression of the external structure of body is

4.   Cast fossils –

Sometimes minerals fills in the mould, resulting in cast fossils   

5.   Print Fossils –

Foot print or prints of wings, skin,leaves, stems etc made in soft mud which subsequently become fossilized are a common type of fossils .

These fossils include the fossil preservation of contents of the intestine or excreta of many ancient

animals including particularly the reptiles or fishes.

By studying fossils following facts about organic evolution are evident –

1.   Fossils found in older rocks are of simple type and those found in newer rocks are of complex types.

2.   In the beginning unicellular protozoans were formed from which multicellular animals evolved.

3.   Some fossils represents connecting links between two groups

Evolution of Horse

Evolution of horse was described by C.marsh.

The primitive fossil of the horse was   found in North America named Eohippus.

Changes during evolution of horse are as follows –

1.   Increase in body height

2.   Increase in the length of neck

3.   Development of high crown on the surface of teeth and formation of cement.

4.   There is gradual increase in the length of  legs.

5.   Number of toes or fingers in legs have reduced in modern horse. Only middle toe touches the ground, other toes reduced gradually.  

6.   Legs become more powerful for fast running

7.   As new species were formed, previous ones becomes extinct.

8.   Enlargement of brain size.

Fossils of important Ancestors of horse

1.   Eohippus or Hyracotherium –

It evolved in Eocene Epoch.

It's size was like a fox.

(Orohippus : It evolved in middle Eocene epoch.)

It evolved from eohippus during Oligocene epoch.

It's size was like a sheep.

(Miohippus : In the late oigocene Mesohippus was replaced by another slightly advanced horse like form named miohippus. It was much like mesohippus in a appearance but some what large in size)

(Parachippus : It evolved in early miocene).

3.   Merychippus –

It evolved in middle and upper miocene epoch. It's size was like a donkey.

This horse evolved during pliocene epoch. It was of the size of modern pony.

This is modern horse which evolved from pliohippus during pleistocene epoch (height 60-64 inches).

''Dating of fossils''  or ''The clock of the Rock''

The fossils give valuable information about the history of organic evolution by giving information about the organisms which existed in the past.

This is possible only if the correct age of the fossils can be determined. Methods have been developed to find out the correct age of the fossils by determining the age of the rocks  where the fossils are found.

Rocks have been found to contain certain radioactive elements which lose their radioactivity and change into other nonradioactive isotopes at a fixed rate irrespective of the environmental conditions prevalling at different times.

If the rate of this loss of radioactivity of an element is known, the relative proportions of the Quantities of radioactive and nonradioactive element in a given rock will enable us to find out the age of the rock.

This method is called absolute dating.

This will be illustrated with the help of four different methods.

(3)  Potassium – Argon method

(4)  Electron spin resonance method (ESR method)

Geological Time Scale – Firstly given by Giovanni Avduina.

Chronological order of the history of organic evolution, which is presented in the form of geological time scale.

This time scale includes the history of earth itself ever since it was formed to formation of its crust from lava of ancient volcanic eruptions.

The period between the origin of gaseous clould (4.6 billion years ago) from which the earth was formed and the formation of earth's crust is called Azoic Era (era of no life).

The remaining period (about 4.0 billion years) is divided in to five Eras namely –

The Archaeozoic Era had ''invisible life'' and the remaining four era had ''visible life'' (Phanerozoic). Archaeozoic and proterozoic eras are also grouped together as Precambrian because the first part of palaeozoic is Cambrian.

The three eras namely palaeozoic, mesozoic and coenozoic, each is further divided into smaller time spans called Period and the periods of coenzoic era are each further subdivided into Epochs.

It is also believed that each era of earth's history started with a revolution or cataclysm and ended with yet another revoluation.

These revolutions meant intense geological disturbances that occurred on earth, so that most of the pre-existing organisms perished in each revolution and the few remaining ones evolved into new and varied organisms.

The first great revolution is believed to have occurred between archaeozoic and proterozoic eras.

The second great revolution between proterozoic and palaeozoic eras.

Applachian revolution between palaeozoic and Mesozoic eras.

Finally the rocky mountain revolution between Mesozoic and coenozoic eras.    

Fossils park of India –

1. Birbal sahni institute of palaeobotany, Lucknow.

2. 50 million year old fossil forests preserved in mandla district Madhya Pradesh.

3. 100 million year old fossil forest in rajmahal hills Bihar.

4. 260 milllion year old Coal forming forest in Orissa. 

2.   Morphological and Anatomical Evidences –

Different animals and plants show dissimilarities in their structure but in some characters they show

similarities. These similarities are of two types.

The similarity based on common origin, similar basic plan of organization and embryonic development is

called homology.

Similarity in appearance and function is not necessary.

The organs which have common origin, embryonic development and same basic structure but perform

different functions are called Homolgous organ. Homologous term given by Richard Owen.

Examples of Homologous organs –

(i)   Forelimbs of mammals –

In their fore limbs similar bones are present like – humerus, radius, ulna, carplas, metacarpals and
phalanges.

(ii)  Legs of invertebrates –

But in both segmented legs are present are segments are same like coxa, Trochanter, Femur, tibia,  1-5 jointed tarsus.  

(iii)    Mouth parts of insects

Biting and chewing      Chewing and lapping      Piercing and sucking

In each of these insects the mouth parts comprise labrum, mandibles and maxillae.

(iv) Homology is also seen in the skeleton, heart, blood vessels and excretory system of different vertebrates.

(v) Thorn of Bougainvillea and tendril of cucurbita (Modification of axillary bud).

(vi)  Wings of sparrow and pectoral fins of fish.

(vii) Hind limb of mammals.

(viii)  Potato & ginger.

(ix)  Radish & Carrot

(x) Homology is also seen amongst the molecule. This is called molecular homology. For example the proteins found in the blood of man and apes are similar.

(xi)    Testes in male and Ovaries in female develop from same embryonic tissue.

(xii)   Pectoral fin of fish and flipper of seal.

(xiii)  Flipper of penguin (bird ) and dolphin (mammal)

Divergent evolution (adaptive divergence/adaption radiation)  

Homology found in different animals indicate their evolution from common ancestors.

Species which have diverged after origin from common ancestor giving rise to new species adapted to new habitats and ways of life is called adaptive radiation, exhibit large number of  homologous organs.

Homology shows Divergent evolution.

For Example Adaptive radiation gave rise to a varity of marsupials in Australia.         

It is similarity in organs based on similar function.

Organs which have different origin and dissimilar fundamental structure but have similar function are called Analogous organs.

Examples of Analogous organs –

(i)    Wings of bat & birds are analogous to wings of insects.

(ii)    Pelvic fins of fish, flipper of seal

(iii)   Sting of bee and scorpion.

(iv)  Phylloclade of Ruscus and leaf

(v)    Chloragogen cell of pheretima and liver of  vertebrate

(vi)   Hands of man and trunk of elephant

(vii)  Potato and sweet potato.

(viii) Eyes of Octopus and eyes of mammals (different in their retinal position).

Convergent evolution (adaptive convergence/parallel evolution)

Development of similar adaptive functional structures in unrelated groups of organisms is called convergent evolution. 

For Example : Some of the marsupials of Australia resemble equivalent placental mammals that live in similar habitats of other continents.    

When adaptive convergence is found in closely related species, it is called parallel evolution.

Analogous organs do not show common ancestory but they show evolution.

3.   Evidences from vestigial organs –

The organs which are present in reduced form and donot perform  any function in the body but correspond to the fully develop functional organs of related animals are called vestigial organs.

They are remanants of organs which were complete and functional in their ancestors.

Vestigial organs in Human body –

Human body possess about 180 vestigial organs

Vestigial organs in other animals –

–    Hind limb and pelvic girdle of python

–    wings of flightless birds such as ostrich, Emu, Kiwi, Dodo, Reha etc. (Dodo recentely extinct)

–    splint bones in feet of horse [2 nd and 4 th finger]

–    rudiment of reptilian jaw apparatus.

–    Hindlimb and pelvic girdle of whale.

Vestigial organs in plants –

Scale leaves of Ruscus and various underground steams.

Vestigial organs are example of lamrckism (Theory of inheritance of acquired character)

4.   Evidences from connecting links –

Some animals and plants possess characters of two separate groups. One being primitive and the other is advanced group.

These species as bridge between two taxonomic groups such organism are called connecting link. They

provide good example of organic evolution of common ancestory.

(i)      Virus : between living and non living

(ii)     Euglena : Between plants and animals

(iii)    Proterospongia : Between protozoa and porifera

(iv)    Neopilina : Between mollusca and annelida

(v)     Peripatus : Between Annelida and arthropoda

(vi)    Archaeopteryx : Between reptiles and birds

(vii)   Balanoglossus : Between nonchordates and chordates

(viii)  Chimera : Between cartilaginous fish and  Boney fish

(ix)    Lung fish (Protopterus) : Between fishes and amphibia

(x)     Platypus : Between reptiles and mammals

(xi)   Echidina : Between reptiles and mammals.

5.   Evidences from Atavism (Reversion)  –

Sometimes in some individuals such characters suddenly appears which were supposed to be present in their
ancestors but were lost during the course of development.

This phenomenon is known as atavism or reversion. Atavism proves that animals developing atavistic structure have evolved from such ancestors in which these structures were fully developed.

1.   Human baby with tail

2.   Cervical fistula– in some human babies an aperture is present on neck behind the ear called as
      cervical fistula. It represents pharyngeal gill slits which were present in aquatic vertebrate ancestors.

3.   Long and pointed canine teeth represented carnivorous ancestors.  

4.   Large and thick body hair reflect our relationship with apes.

6.   Evidence from physiology and biochemistry –

Different organism show similarities in physiology and biochemistry. Some clear examples are –

1.   Protoplasm : Structure and chemical composition of protoplasm is same from protozoa to mammalia.

2.   Enzymes : Enzymes perform same function in all animals like Trypsin digest protein from amoeba to man. Amylase digest starch from porifera to mammalia.  

3.   Blood : Chordates show almost same composition of  blood.

4.   ATP : This energy rich molecule is formed for biological oxidation in all animals.

5.   Hormones : Secreted in different vertebrates performs same function.

6.   Hereditary material : Hereditary material is DNA is all organism and its basic structure is same in all
            animals.

7.   Cytochrome C is a respiration protein situated in the mitochondria of all organism. In this protein from
            78-88 A.A. are identical in all organism, which show common ancestory.

Physiology and biochemistry thus prove that all animals have evolved from some common ancestor.    

7.   Evidences from bio geographical distribution –

The study of geographical distribution of animal and plant species in different parts of earth is called
Biogeography.

Different animal species occurring in an area are called Fauna and those of plants are called Flora.

On the basis of fauna and flora Alfred Russel Wallace divided the whole world into six major biogeographical regions called realms.

Nearctic : North America fro Mexixan highlands to Arctic islands and Greenland.

Palaearctic : Europe, North Asia up to Himalayas and North Africa up to Sahara desert.

Neotropical : Central and South Amerial, Mexican lowlands and West Indies.

Oriental : Asia, South of Himalayas India, Ceylon, Malay, Peninsula, Sumatra, Bornea, Java Celebes and
      Philippines.

Ethiopian : South Africa from Sahara Desert, Madagascar and Adjacent islands.  

Australian : Austrialia, Tasmania, New Guinea, New Zealand and Oceanic islands of the pacific. It is believed that millions of years ago all the continents were present in the form of a single land mass called Pangaea.

Later on due to varies geological changes, these continents drifted fro one another.

As these continents moved away, they got separated from each other by the seas. As these continents had different environmental conditions so plants and animals evolved there were of different varieties. (New species).

Palaearctic and oriental realms are separated by high Himalayan Mountains.

1.   Prototheria –

This is sub class of mammalian, which includes egg laying mammals like Platypus and Echidna found

After the evolution of prototherians from reptiles Australia got seperated from mainland of Asia.

Later on Eutherian mammals evolved in Asia, Due to their carnivorous nature they destroyed prototherians and metatherians from Asia.

So these groups became extinct on the mainland but they survived in Australia due to absence of Eutherians.

Today eutherians are also found in Australia (they were later transported by man).

2.   Marsupialia – The subclass of class mammalian includes kangaroos and Opossum which are found only
in Australia.

3.   Darwin's finches – Darwin studied Fauna and Flora of Galapagos island situated near south America       (consisted 22 islands). Here he saw 22 types of finches (birds) .

A related species of these birds were also present in South American continent.

Probably some member of this species migrated to Galapagos island where these birds evolved into different species as a result of adaptation to environment.

These birds are now known as Darwin's Finches.

Darwin described that a particular species is evolved in a particular area, progenies of this species migrate to different geographical areas and are gradually adapted to changing environmental conditions.

These adaptations gradually give rise to new species as a result of isolation.

Special Point :

a. Darwin's finches are also an example of adaptive radiation (different shape of beak and claws due to their habitat)

b. Darwin's finches are example of allopatric speciation.

4.   Elephants and lions are mainly found in Africa and India.

5.   Giraffe, Zebra and hippopotamus are found only in Africa. 

6.   Main land of human evolution in Africa.

Important Point :

Palaeontological and Biogeographical evidences are considered as best evidences in support of organic evolution. 

8.   Evidences from Embryology –

Baer's Law : An organism show its ancestor stages in embryonic development. In embryonic stage general characters appear first then specialized characters appear. 

Muller : First to propose 'Recapitulation theory'.

–    According to it 'ontogeny recapitulate phylogeny' it means any organism show its ancestral adult stages during its embryonic development.

It shows that all organism evolved from a common ancestor.

–    Ernest Haeckel explained it in detail and gave the name 'Biogenetic law'

Examples : -

(i)   The Zygotes from which the development of all metazoan bodies starts, are single-celled and quite comparable with the Bodies of simple protozoans.

This indicates the origin of Metazoans from Protozoan Ancestors.

(ii)     The early stages of Embryonic development, Viz. Morula, Blastula and gastrula are Basically similar in
         all metazoans, indicating a Monophyletic Origin of the latter. 

(iii)    The Phylogenetically earliest metazoans i.e., the sponges and cnidarians, have retained early gastrula like double – layered (Diploblastic) structure of Body of Metazoans.

(iv)   In fishes,  the young individual, developing from gastrula, is almost-like the adult, but the tadpole larvae
of Amphibians bear more resemblance to the young once of fishes than to their own Adults. This indicates
Origin of Amphibians from fishes.

(v)  Even after gastrulation in the vertebrates, the early postgastrula stages are quite similar in members of all
the different classes, Viz, fishes, amphibians, reptiles, birds and mammals.

The differentiation of class characters appear in later stages, moreover, the embryo of phylogenetically
higher vertebrates pass through the adult stages of lower vertebrates before finally attaining the characters of  their respective classes.

This proves that All Vertebrates have evolved from common fish like Ancestors and also that both Birds and mammals have evolved from reptiles.         

(vi)    When the heart develops in the embryos of Amphibians, reptiles, Birds and Mammals, it is 2-chambered same as in the embryos and Adults of fishes. In later stages of Embryonic development in Amphibians, reptiles, the heart become, 3-chambered. In Birds and Mammals the heart is 4-chambered in the last embryonic stages to continue as such in the Adults.

(vii)   Modern Scientists have discovered ''Biochemical recapitulation'' also.

For example, fishes mainly excrete Ammonia. Adult Amphibians Excrete urea, but their tadpoles excrete Ammonia like the fishes.

Birds excrete uric acid, but their embryos excrete first Ammonia and then urea during earlier stages.

(viii)  In embryonic stage birds showed tooth buds for some time, which became extinct later. It show that birds evolved from toothed reptile like ancestors.

Plants and Animals show a great diversity of form. They also show some similarities among themselves.

It is on account of these differences and resemblances that the taxonomists have to arrange them in to smaller and larger groups.

Amongst species also there are differences and resemblance of varying degree. Some species resemble one another more closely than they resemble others and form a closely related group.

Similarly, there are other groups of closely resembling species.

The members of each group resemble each other more closely than they resemble the members of other groups.

Each such group of species is called a genus. Genera also show different degrees of resemblances amongst themselves.

Those that resembles one another more closely than others are placed in a large group called a family.

Families are grouped in to larger units called orders, orders into classes and classes in to Phyla.

Evolution has a ready explanation for this system of grouping or classifying plants and animals in groups indicates relationship.

Special points  : -

1.   The aquatic mammals [eg. Dolphins, Whales, Seals, Porpoises etc.] don't have gill slits-because their adaptation to aquatic life is secondary.  

2.   In Acacia tree well developed compound leaves are found. But seedling has simple leaves like those found in all stages of development of its ancesters. This provide a good example of – Recapitulation

3.   Modern day Oaks of southern United State of America retain their foliage throughout  the year where as the oaks of northern United States are deciduous and shed their leaves during water. The southern species, on the basis of this character of leaves are considered to be more primitive than the northern oaks. However, the seedling of northern species are generally seen to retain their leaves during winter. This provide a good example of - Recapitulation

4.   EVOLUTIONARY TREND :

The continuous change of a character within an evolving lineage is termed as evolutionary trend.   

THEORIES OF ORGANIC EVOLUTION

First teory of evolution was proposed by

Jean Bapttiste de Lamarck (17-44 - 1829)

Book : Philosophie Zoologique (1809)

Lamarck coined the terms – Invertebrates, Annelida.

The term Biology was given by Lamarck & Treviranus.

 

Theory of Inheritance of Acquired Character

Basic Concept of Lamarckism–

(i)   Internal Vital Forces :

Some internal forces are present in all organisms. By the presence of these forces organism have the tendency to increase the size of their organs or entire body.

(ii)  Effect of environment and new needs:

Environment influences all type of organisms. Changing environment gives rise to new needs. New needs or desires produce new structures and change habit of the organism.

(iii) Use and disuse of organs:

If an organ is constantly used, it would be better developed whereas disuse of organ result in its degeneration.

(iv) Inheritance of acquired character:

During the life of an organism new character develop due to internal vital forces, effect of environment, new needs and use and disuse of organs.

These acquired character are inherited from one generation to another. By continuous inheritance through many generation these acquired characters tend to make new generation quite different from its Ancestors resulting in the formation of new species.

Example in support of Lamarckism :

1.   Long neck and high fore limb of Giraffe. 

2.   Aquatic birds stretched their toes and developed web.     

4.   Deers became good runners by the development of strong limbs and streamlined body.

5.   Retractile claws of carnivorous animals

Criticism of Lamarckism -

1.   According to first concept organism tends to increase their size but it is not universally true.

For Example among angiosperm the trees seem to be primitive and the shrubs, herbs and grasses have evolved from trees but the size was reduced during evolution.      

2.   Second concept is false. Can we sprout wings wishing to fly like birds.

3.   The third concept is some what true like the well developed biceps muscles of blacksmith and less developed wings in flight less birds.

But this concept also have many objections like the eyes of a student/reader do not increase in size and power with increasing age, the constantly beating heart maintains a constant size through generation.

4.   Fourth concept is completely false because acquired characters are not inherited.

      Weismann cut off the tails of rats for about 22 genrations but there was no reduction in the size of tail on the basis of this experiment Weismann proposed the theory of continuity of germplasm.   

        (i)    Two types of matters are present in organism, somatoplasm and germplasm.

        (ii)   Sometoplasm in somatic cells and germplasm in Germinal cell.

        (iii)       Somatoplasm dies with the death of organism while germaplasm transfers into the next generation.

        (iv)  If any variation develops in germplasm, it is inherited , while if variation develop in somatoplasm it is not transmitted.

      Pyane kept drosophila in dark up to 69 generation, but there was no reduction in the size or sight of eyes

–    Boring of ear and nose in Indians.

Neolamarckism-Term by Packard

Although Lamarckism remained controversial but some scientists gave the following evidences in favour of Lamarckism. The are known as neo-lamarckians.

According to neolamarckism environment effected the inheritance of acquired charater. According to it changing environment give rise some physical and chemical changes in organism, which effect their germplasm, and these acquired characters are definitely inherited.

1.   Sumner's Experiment–

Sumner kept white rat in warn temperature resulting in elongation of body, large pinna and long tail. These features were inherited by the offspring.

2.   Kammerer's Experiment–

Kammerer kept salamander in dark background. The black spots found on skin were widely spread. In lighter, background the skin became yellow with limited black spots. These character were inherited by the offspring. 

3.   Mc Dugal's Experiment-

Mc Dugal trained white rats to cross a tank of water following a definite route. These trained rats were mated and their offspring were again trained. It was observed that there was decrease in the number of errors by offsprings of white rats.

DARWINISM

Charles Robert Drawin was born on 12 th feb. 1809 in England. Darwin traveled by H.M.S. Beagle.

The ship left on Dec. 27, 1831 and returned on Oct. 2, 1836. He travelled South America, South Africa,
Australia and Galapagos Islands.
Darwin was influenced by two books.

"Principles of population" of Malthus.

"Principles of Geology" of Charls Lyell.

Alfred Russel Wallace :

He travelled South eastern Asia and South America. The idea of natural selection striked in his mind. Wallace wrote an essay and sent it to Darwin. "On the tendency of varieties to indefinitely from original type".

There was striking similarity between the view of Darwin and Wallace.

Wallance's chart :  Wallace presented a chart to explain main points of theory of Darwin:

"Darwinism" or "The theory of Natural Selection" was proposed by both Charles Darwin and A.R. Wallace.

This theory was later on explained by Darwin in his book 'On the origin of species by the means of Natural Selection' (1859).

The main features of theory of Natural Selection are as follows –

(1)  Over production : (High rate of Reproduction)

All organisms have capability to produce enormous number of offspring, organisms multiply in geometric ratio.

e.g. – Plants produce thousands of seeds.

– Insects lay hundreds of egg

 – One pair elephant gives rise to about six offspring and if all survived in 750 year a single pair would produce about 19 million elephant. Thus some organisms produce more offspring and other produce fewer offspring This is called differential reproduction.

(2)  Struggle for existence :

Every individual competes with other of the same and other species for basic necessities like. Space, shelther and food. It is called struggle for existence and it continues for the whole life from zygote stage to its natural death.

(3)  Variations and heredity :

Exept identical twins no two individuals are similar and their requirements are also not same.It mean there are differences among the individuals. These differences are called variations.

Due to variations some individuals would be better adjusted towards the surroundings than the others.

According to Darwin the variations are continuous and those which are helpful in the adaptation of an organism towards its surroundings would be passed on to the next generation, while the others will disappear.

(4)  Suvival of the fittest or natural selection :

The original idea of survival of fittest was proposed by Herbert Spencer.

According to Darwin most suitable and fit individuals are successful in struggle for existence.

The individuals with most favourable adaptations are able to lead most successful life and are able to win over their mating partners.

Darwin called it Sexual Selection.

In the struggle for existence only those members survive which posses useful variations means nature selects fit individuals.

This was called Natural Selection.

Fitness is the end result of the ability to adapt and get selected by nature.

(5)  Origin of New Species :

Darwin explained that variations appearing due to environmental changes are transmitted to the next generation.

So offspring become different from ancestors. In nest generation process of Natural selection repeats so after many generation a new species is formed.

Criticism of Darwinism –

1.   Darwin does not explain the development of vestigial organs.

2.   No satisfactory explanation for the cause, origin and inheritance of variation.

3.   Darwin is unable to explain why in a population only a few individuals develop useful variation and others have harmful variations.

4.   Criticism of Darwinism was based on sexual selection. Why only female selects the male for mating why not vice versa.

5.   Darwin was unable to differentiate between somatic and germinal variations.

6.   This theory was unable to explain over-specialization of some organs like tusk of elephants, antelers of deer.

7.   This theory only explain the survival of fittest but unable to explain arrival of fittest.

8.   The main drawback of Darwinism was lack of the knowledge of heredity

Theory of pangenesis

According to this theory all organs of an individual produce Pangenes, which are minute particles carrying information about the organs.

The pangenes traveling through the blood stream will ultimately reach the gametes, so that each gamete will have pangenes for each of the different organs.

After zygote formation, the pangenes tend to form the same organs from which these pangenes were produced.

NEODARWINISM :

NeoDarwinism is a modified form of Darwinism along with recent researches of Weismann, Mendel,
DeVries, Huxley, Gates, Stabbins
ets. They performed many experiments to remove the objections against Darwin's theory.

The salient features of neodarwinism are as follows–

1.   Rapid multiplication : All organism multiply in geometrical ratio.

2.   Limited food and space : Food and space are limited.

3.   Struggle for existence : It is of three types. Intraspecific, Interspecific and environmental.

      The struggle for existence is of three types –

      (i) Intra-specific struggle : It is competition between the individuals of same species for same needs like food, shelter and breeding (most acqute type of struggle).

      (ii) Inter-specific struggle : It is the struggle between the individuals of different species for food and shelter.

(iii) Environmental struggle : This struggle is between the organism and their environment. All organism struggle with cold, heat, wind, rain drought and flood etc.

4.   Genetic Variations : They are inheritable variation which can occur due to the following reasons.

(a)  Mutation : They are discontinuous variations which develop due to permanent changes in genotype. Mutations are of three types –

         Genomatic mutations : Change in number of chromosome.

(b)  Gene recombination : They are new combination of genes which are usually caused by crossing over.

(c)  Hybridisation and gene migration : It is crossing of organisms which are genetically different in one or more traits.

(d)  Random Genetic drift : It is the elimination or addition of the genes of certain chartain characters when some animals in population migrate or dies or immigrate. It changes the gene frequency of remain population. Genetic drift operates only in small population.

(Changes in frequency of genes in a gene pool is called drift)

Founder Effect :    Gene pool is the sum total of all the genes found in a population.

Change in the frequency of gene in a gene pool is called genetic drift.

Genetic drift always operates in small population.

By genetic drift often the phenotype of this small population quickly become different from the parental population and some time form a new sp. Such an effect is called Founder Effect.

Bottleneck Effect : Death of several members of population due to natural calamities (Earthquake , Storm, Flood) also leads to genetic drift.

The original size of population is then restored by mating among the survivor.

The new population may lack the genes of certain.

This may produce a new species after some time.

The loss of a section of population by death an after sometime a new species is formed that effect is known as Bottleneck effect.

5. Natural Selection :

If differential reproduction (some individuals produce more, some only few and still others none) continue for many generations, genes of the individuals which produce more offspring will become predominant in the gene pool of the population.

Thus natural selection occurs through differential reproduction in successive generations. 

6.   Isolation :

Isolation is a segregation of populations by some barriers which prevent interbreeding.  The reproductive isolation between the populations due to certain barriers leads to the formation of new species.

Example of Natural Selection –

(1)  Industrial Melanism :

This phenomenon was studied by Barnard kettlewell.

Before industrial revolution, the dull grey forms of prepared moth-Biston betularia – were dominant the Carbonaria form (Black) was rare because it was susceptible to predation by birds.

The industrial revolution, resulted in large scale smoke which got deposited on tree trunks tuning them Black. Now grey varieties became susceptible – the black forms flourished.

Replacement of coal by oil and Electricity reduced production of black moth so the frequency of grey moths increased again.

(2)  Drug resistance :

The drugs which eliminate pathogens become ineffective in the course of time because those individuals of pathogenic species which can tolerate them, survive, flourish to produce tolerant population.

(3)  Sickle cell Anaemia and Malaria :

Individuals homozygous for sickle cell Anaemia die at an early age.

In heterozygous individuals, the cells containing abnormal haemoglobin Sickle shaped.

In fact, When an RBC becomes sickle-shaped, it kills Malarial parasite effectively so that these individual area able to cope with malaria infection much better than normal persons.

The processs of natural selection thus maintains the abnormal form of haemoglobin along with the normal form in a region where Malaria is common.

(4)  Malaria and G-6-PD deficiency :

Glucose 6- Phosphate dehydrogenase deficiency  is a common abnormality in Negroids. Haemoglobin gets denatured and is deposited on cell membrane.

The disease is called favism. In these RBC, the malarial parasite cannot complete It's cycle.

Such persons get protection from Malaria.

Artificial Selection –

Man has been taking the advantage of genetic variations for improving the qualities of domesticated plants and animals.

He selects the individuals with desired characters and separates them from those which do not have such characters. The selected individuals are interbred.

This process is termed as Artificial Selection. This process is man made.

If it is represented for many generations it produces a new breed with desired characters.

By artificial selection animal breeders are able to produce improved varieties of domestic animals like dogs, horse, pigeons,, poultry, cow, goats, sheep and pigs from their wild ancestors. Similarly

the plan breeders have obtained improved varieties of useful plants like wheat, rice, sugarcane, cotton, pulses vegetables fruits etc.

Artificial Selection is similar to natural selection except that the role of nature is taken over by man and the character selected are of human use.

The breeders have successfully produced the toy-like Shetland pony, the Dane dog, the sleek Arabian race horse by selection.

Many crop plants like broccoli, kale cabbage, Cauliflower, Brussels sprouts and kohirabi have been produced through selective breeding.

The various breeds of fowl ranging from the ceremonial cocks (the Japanese onago-dori) to the broiler. leghorns are all derived from a single jungle fowl Gallus gallus.

Reproductive Isolation –

Reproductive isolation is the prevention of inter breeding between the population of two different or closely related species.

It maintains the characters of the species but can lead to the origin of new species.

The mechanism the characters of the species but can lead to the origin of new species.

The mechanism of reproductive isolation is explained by Stebbins in his book 'Process of Organic Evolution'.

Two main subtypes of reproductive isolation are–

1.  Premating or prezytotic isolation :

Prevent matting or formation of zygote.

      (1)  Ecological isolation : Two species live in different habitats and do not meet. (One may be living in fresh water and the other in the sea).           

      (2)  Temporal isolation : Breeding seasons or flowering time may be different in the two species.         

      (3)  Behavioural isolation :  The males of one animal species are unable to recognize the females of another species as potential mates.

      (4)  Machanical isolation : The structural differences in genitalia of individuals belongings to different animal species interfere with mating.

      (5)  Gametic isolation : The sperms and ova of different species of animals are unable to fuse. In plants, the pollen coming from a different species may be rejected by the stigma.

2.   Postzygotic Isolation  : A hybrid zygote is formed but it may not develop into a viable fertile adult.

(1) Hybrid inviability : Hybrid zygotes fail to develop. In plants, embryos arising from interspecific crosses abort.

(2)  Hybrid sterlity : Hybrid adults do not produce functional gametes. (Mules and henny are common example) in mammals. Several hybrid ornamental plants are sterile.

3.   Hybrid breakdown  : Sometime inter specific mating produce a hybrid, which give rise to next hybrid by back cross but they have reduced vigour or fertility or both.

GENETIC BASIS OF ADAPTATIONS :

Joshua Lederberg  & Esther Lederberg  shown genetic basis of adaptations by experimenting on bacteria. This experiment is known as Ledeberg's Replica plate experiment.

1.    Lederberg cultured the bacterial cells on agar plate.

      Many bacterial colonies or groups grew on this agar plate.

      In this every colony is formed  by the division of bacterial cells.

      Therefore its all cells were of same genetic structure.

     This type of group of cells is known as clone.

      This multi colony agar plate is known as master plate.

2.   On this master plate one sterile velvet plate was pressed slightly so that some bacteria got stuck on velvet plate. In this way this becomes replica of master plate.

3.   Now efforts of preparing replica had been made on those agar plates whose agar contains an antibiotic penicillin. It was seen that some bacteria failed to grow on penicillin agar plate while some bacteria were able to grow and developed new colony.

It was concluded that these bacterial colonies were penicillin resistant.

These bacteria have penicillin resistant mutant gene.

* Lamarckian view : Penicillin induced a change in some bacterial cells enabling them to grow in medium containing penicillin (wrong concept).

** According to Darwin some bacterias were penicillin resistant in bacterial suspension. In penicillin medium normal bacteria did not survive while mutant bacterias survived, as they are adapted, and form colony.

MODERN SYNTHETIC THEORY OF ORGANIC EVOLUTION - Evolution, Biology, Class 12 

MODERN SYNTHETIC THEORY OF ORGANIC EVOLUTION  :

This theory is the result of the work of a number of scientist namely Dobzhansky, Fisher, Haldane, Swall wright, Mayr, Stebbins. 

Stebbins discussed this theory in his book ''Process of Organic Evolution'' and Dobzhansky explained it is his book ''Genetics and the origin of species''.

According to this theory new species can not evolved by the presence of variable genotype in  a population. Two factors are also required-natural selection and reproductive isolation.

Natural selection guides different population in to different adaption direction and reproductive isolation between them due to geographical barriers leads these direction to the evolution of new species.

In this theory following factors are included  –

(ii)  change in chromosome number and structure

(iii) Genetic recombination

Besides these factors there are two more processes which cause evolutionary changes. These are –

      (i)   Migration of individuals from one population to another.

      (ii)    Hybridisation among species and also related genera which causes genetic variation in the population  undergoing process of evolution.

Proposed by Hugo-de-vries on the basis of his experiments on a plant Oenothera lamarckiana.   

Main Point of mutation theory :

1.   Mutation or discontinuous variation are the raw material of evolution.

2.   Mutation appears suddenly and produced their effect immediately.

3.   Mutants are different from the parents and there are no intermediate stages between the two.

4.   The same type of mutation can appear in several individuals of a species.

5.   Mutation can appear in all direction and all mutations are inheritable.

6.   useful mutations are selected by nature and lethal mutations are eliminated.

7.   Mutation are recurring so that the same mutant can appear again & again so change of selection by nature are increased and new species is formed.

8.   De-vries termed single step large mutation as saltation.

9.   Mutations are large, random and directionless while Darwinism variations are small and directional.

Points in favour of mutation theory :

1.   Mutations are actually the source of all variations and fountainhead of evolution.

2.   Mutation theory can explain both progressive & retrogressive evolution.

Significance :

De-vries mutation theory generally accepted because the mutation were found to be inheritable. It was later through that evolution cannot occur by mutation alone, natural selection and isolation of mutants are also necessary for evolution.

Natural Selection & Polymorphism :

A population is called polymorphic for a character if two or more distinct form are present in this population.

Ex.: ABO Blood Group :

There are 4 types of blood group are present in human being A, B, AB. and O. They are due to the presence
of different genotype.

Sickle cell anemia is also an example of polymorphism. In this disease on amino acid is changed in
polypeptide chain due to change in one N2 base. That's why the normal shape of RBC is changed into sickle
shape.

The organism in which heterozygous condition is present for this characters, the RBC become sickle shaped.
In this type of RBC malarial parasite can't have a normal growth that's why these individuals are resistant
towards malaria.

The HbS, HbS, condition leads to the death of organism.

The organism with HbS, HbA condition are selected by nature because these are the fittest of all. The lose of HbS gene due to the death of organism having HbS, HbS is recovered & balanced by the reproduction of
heterozygous condition (HbS, HbA).

This type of selection is called balancing selection.

It means the  preservation of genetic variability is maintained by the selection of hertozygotes which is called
'Balanced polymorphism'.

But this kind of balancing selection is found very rarely in nature.

Types of Natural Selection :

Based upon different organism – environment relationship. Following different kinds of natural selection
have been recognised.

(1)  Stabilising selection :

Stabilizing selection operates when phenotypic feature coincide with optimum environmental conditions and competition is not present.

It keeps a population genetically constant.

It favours the average or normal phenotypes and eliminate the extreme variants, that fall towards both ends of the bell-shaped curve of variability for the distribution of measurements of phenotypic traits.

Due to continuous elimination of both extremes, the bell shaped curve tends to narrow.

Stabilising selection always operates in constant or unchanging environment.

Ex. Mortality in babies : The birth weight of human babies provides another example influenced by stabilizing selection.

The optimum birth weight favoured by stabilizing selection is 7.3 pounds.

New born infants less than 5.5 pounds and more than 10 pounds have the highest mortality rate. The curve for mortality is virtually the complement of the curve of survival.      

(2)  Directional selection or Progressive selection :

Directional selection produce a regular change in a population in respect to certain traits.

This form of selection operates in response to gradual changes in environmental condition.

It favour the phenotype which is non average or extreme and then pushes the phenotype of the population in that direction.

Directional selection removes more individuals from one end of the normal curve of variability distribution and adds towards the other end and alters the mean value of the trait in the population in a particular direction.

So the mean moves in one direction.

Directional selection operates when environment is changing in one direction.

(3)  Disruptive selection :

This is probably the rarest form of selection but can be very important in bringing about evolutionary change.

Presence of more than one phenotype in a population.

Selection pressure acting from within the population as a result increased competition may push the phenotype away from the population mean towards the extremes of the population.

This can split a population into two subpopulation.

If the gene flow between the subpopulation is prevented, each population may give rise to a new species. In
some cases this form of selection can give rise to the appearance of different phenotype within a population,
known as polymorphism.

Eg. Shell pattern in limpets : Shell patterns of limpets (marine mollusca) present a continuous, ranging from pure white to dark tan. These are either attached to white goose neck barnacles or to tan-coloured rocks. The white or light-coloured limpets camouflaged withy white barnacles and tanned ones were protected on the tan-coloured rocks. Limpets of intermediate shell patterns, being conspicuous are preyed by predatory shore birds, resulting in distruptive selection.

Formation of one or more new species from an existing species is called speciation. Speciation are of 2
types.

A.  DIVERGENT SPECIATION : Origin of one or more new species from an ancestor species is called
divergent speciation.

In this type of speciation ancestor sp. also continuous to exist with new species.

In this type of speciation no. of species are increased.

Divergent speciation are of two types –

(1)  Allopatric Speciation : When a species split into two or more geographically isolated population and these population finally form a new species.

This mode of speciation is called allopatric speciation and these sp. are known as allopartic species.

Ex. : Finches of Darwin are example of Allopatric speciation.

(2) Sympatric species : In this type of speciation a sub population becomes reproductively isolated from its
parental population.

Sympatric speciation is the formation of species without geographical isolation and these sp. are known as
sympatric species.

B.   Transformation speciation : in this type of speciation an ancestor species change into a new sp. with time. In this process no. of species is not increased.

Transformation speciation are of two types –

(1)  Phyletic Evolution : When an ancestor sp. changed in to a new species by gradual change in thousand of
years.

e.g. Eohippus → Mesohippus → Merychippus → Pliohippus → equus

(2)  Quantum Species : In this process suddenly major changes appears in ancestor species and ancestor species immediately changed into new sp. No. connective links are present in this type of speciation. It is caused by major mutation.

Special point :

Micro evolution : - Micro evolution is the occurrence of small-scale changes in gene frequencies in a
population, over a few generations.

It occurs at or below the species level. It often cause the formation of new subspecies.

These changes may be due to several process-Natural selection, gene flow. mutation, recombination, genetic
drift etc.

Macro evolution : - Macro evolution is the evolution, which results in the production of new adaptive types through a process of population fragmentation and genetic divergence.

It is the occurrence of large-scale changes in gene frequencies in a population, over a geological time period (consisting of lots of micro evolution).

Macro evolution operates above the species level and results in the establishment of new genera, families and order.

The changes in the organization occurs due to accumulation of large mutation (macro mutation).

The divergent evolution of different reptilian group from initial reptile ancestor is example of macro evolution.

Mega evolution : - The origin and evolution of new types of biological organization as a result of general adaptation  from its predecessor  resulting in the formation of new classes, phylum.

Mega evolutionary changes are rare and have occurred only a few times in the evolutionary history of living beings.

Ex. Origin of Amphibia from fishes, origin of reptiles from amphibian, origin of bird and mammal from reptile.

Anagenesis : - It is the evolution of species involving a change in gene frequency in an entire population. It
is also known as phyletic change. Anagenesis may also be reffered to as phyletic species or gradual species.

Cladogenesis : - It is an evolutionary splitting event in which each branch and it's smaller branches form a '      clade' an evolutionary mechanism and a process of adaptive evolution that leads to the development of a
greater variety of sister organism.

HUMAN EVOLUTION

The primates include Prosimians (Lemurs, tarsiers and related forms) and Anthropoids (Monkeys, apes and Human). They are descended from small rodent like or insectivorous mammals that evolved about 80 million years ago.

Order primata is divided into 2 sub orders.

(1)  Old world monkeys : - Rhesus (Macaca), Baboon (Old world = Africa. Asia)

      (2)  Narrow flat nose with downward direction of nostril.

      (5)  Menstruation cycle is present in female.

(2)  New world monkeys : - spider monkey, marmosets (New world = South & Middle America)

      (2)  Protruding nose with upward direction of nostril

      (5)  Menstruation cycle absent but estrous cycle is present.

      So, Old world monkeys are more closer to human.

Human - Hominideae Family

Similarities between man and apes : -

(4)  Hairs are present on body

(5)  Larger head, more cranial capacity

(6)  More intelligent than other animals    

(7)  Facial muscles are present for expression of surprise, pleasure.

(8)  Menstruation cycle is present in female of both

(10) Composition of Hb is same in both. Only one amino acid is different in human and Gorilla.

(11)  Chromosomal similarities : -

(i)   No. of chromosomes are approximately same in man and apes.

(ii)  DNA contents and DNA matching is same in both. This similarity is

100% with Chimpanzee

(iii) Banding pattern of chromosome is same in both.

Comparisons have been made between banding pattern of  chromosomes of man and those of the great apes.

Banding pattern of ch. no. 3, 6 of human and chimpanzee is 100% similar.

Banding techniques enable the identification of individual chromosomes and their parts.

Somatic cells of human contain 46 chromosomes (44 Autosomes and 2-sex chromosomes).

The diploid number of chromosomes in Gorilla, chimpanzee and Oranguttan is 48.

⇒  The total amount of DNA in human diploid cells and that of the great apes are dissimilar.

⇒Similarity in the fine structural organization of the chromosomes is understood only in terms of a common origin for man and chimpanzee.

Differences : -

Human evolution :

      (1)  Propliopithecus : - Origin & evolution in Oligocene epoch so called as Oligocene apes. Evolution
            about 30-35 million years ago.

      (2)  Aegyptopithecus : - Origin and evolution in late Oligocene and Miocene epoch so called as Miocene
            apes.

     (3) Proconsul : - Its fossils were discovered by Leakey from East Africa near Victoria lake in Kenya
           from Miocene rocks. It walked on its four legs (considered as common ancestor of man and apes).

      (4)  Dryopithecus : - Evolution » 15-20 million years ago.

      –    They were forest dwellers spending most of the time one the trees.

–    Origin and evolution in Pliocene epoch.

      –     They are considered as ancestors of human but in characteristics same as Dryopithecus, but   
    spending most of the time on the land.

(8)  Australopithecus :- Prof. Raymond dart discovered a fossil of skull of 5-6 year old baby from the old Pliocene rocks of  Tuang region (S. Africa). He named it Tuang baby, later on he renamed it A. africanus.

–    About 3-2 million years ago it lived in East African grasslands.

–    Evidences shows they hunted with stone. Probably ate fruits.

–     It was an apeman because it have many characters of man and apes so it is also considered as

        connecting link between apes and man.

Apes like characters :

–    Thick growth of hair on body

Man like characters :

–    Complete erect posture (first man who stood erect)

–    Forelimb shorter than hindlimbs.

–    Bipedal locomotion (first man)

–    Some other varities of Australopithecus were also discovered by some other scientist.

–    A. boisei [zinjanthropus] by Leakey from East Africa [Tanzania]

–    A. afaransis [Lucy] by Donald Johanson from Ethiopea.

Prehistoric man : -

A number of other species of Homo appeared and became extinct from time on the evolutionary sense before the origin of homosapiens. These extinct species are called prehistoric species of man.

(1) Homo habilis : - The Tool maker or Handy man.

–    By nature omnivorous, also show cannibalism

(2) Homo erectus : - direct ancestor of homo sapiens

–    Origin and evolution, 1.5 million years ago.

–    Heidelberg man (Branch from main line of Human evolution)

Homo erectus erectus name given by Mayer.

or  Pithecanthropus erectus given by Dubois.    

–    Fossil obtain from central java by Eugene Dubois.

–    They used Tools of bones and stones

    First man who used fire for hunting, protection and cooking

–    Omnivorous, cannibalism have also found.

–    It is also known as erect ape man

Peking man : - Homo erectus pekinensis name given by Mayer 

Sinanthropus erectus name was given by Davidson Black  

–    W.C. Pai discovered the fossil of peking man from China.

–    Used sharp chisel shaped tools of stones, bones for cutting and killing animals.

–    Omnivorous, cannibalism has been also found

–    Used fire for cooking meat and for protection.

Heidelberg man : -

A fossil of lower jaw obtain from Heidelberg in germany it was discovered by Ottoschotensack.

–    Origin & evolution – in Pleistocene epoch. It is believed that this species was evolved as a branch from main line of evolution and got extinct after some time

(3) Homo sapiens : -

–    Cromagnon man  - Direct ancestor of modern man

–    Homo sapiens sapiens - Modern man (Man of today)  

(i)   Neanderthal man : - Homo sapiens neanderthalensis

–    Origin  & evolution before a 30,000 – 1 lakh years

Fossils were discovered by C. fulhrott from Neanderthal vally of Germany.

Ceremonial burial of dead body

Used animals skin as cloths

Beginning of development of speech center.

–    First man believed in ''immortality of soul''

(ii)  Cromagnon man : - Homo sapiens fossils

–    Origin and evolution 34000 years ago.

–    Fossils discovered from Cromagnon rocks of France

–    Cranial capacity - 1650 c.c. (maximum)

–    This man was hunter and used domesticated dogs in hunting, so domestication of animals started
      by cromagnon man.

–    Known for cave paintings.

–    Regarded as the direct ancestor of modern man.

–    By nature carnivorous.

(iii) Homo sapiens sapiens (Modern man) : - Man of today

–    Well developed speech centre, developed languages.

–    Less hairs on body as compared to fossil man

–    It is believed that modern man evolved in Africa.

–    Agriculture was also started by them.

Special Point :

The course of cultural evolution is divided in to three age.

(i)   Bronze age        Age of agriculture, knowledge and use of clothes.

(ii)  Iron age            Present age is also known as Iron age.

Man of future : - homo sapiens futuralis

–    Dr. Shapiro named man of future as Homo futuralis    

–    Tomb like head and larger brain.

      (1)  Anthropology :- Study of evolutionary history of man.

      (2)  Ethology : - Study of animal babbits and behaviour.

      (3)  Hylobates hoolock :- (The Gibbon) is the only ape found in India (forests of Assam)

      (4)  Races of human - 4 types - Caucasoid, Negroid, Mongoloid, Australoid.

      (5)  Hobit : - Recently Rechard Roberts scientist discovered a 18,000 years old fossil of a lady form flors

            island situated near Australia. He gave name it to Hobit/Dwarf man/Homo florasiansis.

BRIEF REVIEW

–    Tree shrews were first real primates.

–    Old world monkeys are more closer to human as compared to new world monkeys.

–    Chimpanzee is closest ape to human.

–    Australopithecus firstly show bipedal locomotion.

–    Homohabilis is also known as handy man or the tool maker man.

–    W.C. Pai discovered the fossils of Peking man from China.

–    Neanderthal man was first man who believed in 'immortality of soul.'

–    Cromagnon man was a painter and regarded s the direct ancestor of modern man.

–    Homosapiens sapiens is the man of today.

–    Carolus Linnaeus called human as Homo sapiens wiseman.

–    Huxley explained origin of man in his book  The man's place in nature'.

–    Darwin explained ancestory of man in his book 'The descent of man'.

–    Human is a member of order primatas of class mammalia.

–    Primates originated 80-100 million years ago in palaeocene epoch of  coenozoic era.

–    Primates originated from elephant shrews but they were not real primates.


The Theory of Evolution Controversy

Today, the theory of evolution is often portrayed in the media as a controversial subject. Primate evolution and the idea that humans evolved from monkeys has been a major point of friction between scientific and religious communities. Politicians and court decisions have debated whether or not schools should teach evolution or if they should also teach alternate points of view like intelligent design or creationism.

The State of Tennessee v. Scopes, or the Scopes "Monkey" Trial, was a famous court battle over teaching evolution in the classroom. In 1925, a substitute teacher named John Scopes was arrested for illegally teaching evolution in a Tennessee science class. This was the first major court battle over evolution, and it brought attention to a formerly taboo subject.


Evolutionary Theorist Concedes: Evolution “Largely Avoids” Biggest Questions of Biological Origins

At this past November’s Royal Society meeting, “New Trends in Evolutionary Biology,” the distinguished Austrian evolutionary theorist Gerd B. Müller gave the first presentation. As we’ve noted before, it was a devastating one for anyone who wants to think that, on the great questions of biological origins, orthodox evolutionary theory has got it all figured out. Instead, Müller pointed to gaping “explanatory deficits” in the theory. Now the Royal Society’s journal Interface Focus offers a special issue collecting articles based on talks from the conference.

Let’s see what Dr. Müller has to say in an article titled, “Why an extended evolutionary synthesis is necessary.” A friend highlights the following paragraph, with his own emphasis added.

As can be noted from the listed principles, current evolutionary theory is predominantly oriented towards a genetic explanation of variation, and, except for some minor semantic modifications, this has not changed over the past seven or eight decades. Whatever lip service is paid to taking into account other factors than those traditionally accepted, we find that the theory, as presented in extant writings, concentrates on a limited set of evolutionary explananda, excluding the majority of those mentioned among the explanatory goals above. The theory performs well with regard to the issues it concentrates on, providing testable and abundantly confirmed predictions on the dynamics of genetic variation in evolving populations, on the gradual variation and adaptation of phenotypic traits, and on certain genetic features of speciation. If the explanation would stop here, no controversy would exist. But it has become habitual in evolutionary biology to take population genetics as the privileged type of explanation of all evolutionary phenomena, thereby negating the fact that, on the one hand, not all of its predictions can be confirmed under all circumstances, and, on the other hand, a wealth of evolutionary phenomena remains excluded. For instance, the theory largely avoids the question of how the complex organizations of organismal structure, physiology, development or behavior — whose variation it describes — actually arise in evolution, and it also provides no adequate means for including factors that are not part of the population genetic framework, such as developmental, systems theoretical, ecological or cultural influences.

Uh, whoa. Or as our friend says, “BOOM.” Read that again. Müller says that “current evolutionary theory…largely avoids the question of how the complex organizations of organismal structure, physiology, development or behavior…actually arise in evolution.” But how stuff “actually arises” is precisely what most people think of when they think of “evolution.”­­­

Says our friend, see Michael Behe in The Edge of Evolution, where Dr. Behe asks, “The big question, however, is not, ‘Who will survive, the more fit or the less fit?’ The big question is, ‘How do organisms become more fit?’” Müller concedes that conventional evolutionary thinking “largely avoids” this “big question.” Though expressed in anodyne terms, that is a damning indictment.

Here are some other gems from the paper (emphasis added throughout):

A rising number of publications argue for a major revision or even a replacement of the standard theory of evolution [2–14], indicating that this cannot be dismissed as a minority view but rather is a widespread feeling among scientists and philosophers alike.

That could have appeared in a work from an intelligent design proponent. But wait, it gets even better:

Indeed, a growing number of challenges to the classical model of evolution have emerged over the past few years, such as from evolutionary developmental biology [16], epigenetics [17], physiology [18], genomics [19], ecology [20], plasticity research [21], population genetics [22], regulatory evolution [23], network approaches [14], novelty research [24], behavioural biology [12], microbiology [7] and systems biology [25], further supported by arguments from the cultural [26] and social sciences [27], as well as by philosophical treatments [28–31]. None of these contentions are unscientific, all rest firmly on evolutionary principles and all are backed by substantial empirical evidence.

“Challenges to the classical model” are “widespread” and “none…are unscientific.” Wow — file that one away for future reference.

Sometimes these challenges are met with dogmatic hostility, decrying any criticism of the traditional theoretical edifice as fatuous [32], but more often the defenders of the traditional conception argue that ‘all is well’ with current evolutionary theory, which they see as having ‘co-evolved’ together with the methodological and empirical advances that already receive their due in current evolutionary biology [33]. But the repeatedly emphasized fact that innovative evolutionary mechanisms have been mentioned in certain earlier or more recent writings does not mean that the formal structure of evolutionary theory has been adjusted to them.

Orthodox Darwinists of the “All Is Well” school meet challenges with “dogmatic hostility”? Yep. We were aware.

Here he obliterates the notion, a truly fatuous extrapolation, that microevolutionary changes can explain macroevolutionary trends:

A subtler version of the this-has-been-said-before argument used to deflect any challenges to the received view is to pull the issue into the never ending micro-versus-macroevolution debate. Whereas ‘microevolution’ is regarded as the continuous change of allele frequencies within a species or population [109], the ill-defined macroevolution concept [36], amalgamates the issue of speciation and the origin of ‘higher taxa’ with so-called ‘major phenotypic change’ or new constructional types. Usually, a cursory acknowledgement of the problem of the origin of phenotypic characters quickly becomes a discussion of population genetic arguments about speciation, often linked to the maligned punctuated equilibria concept [9], in order to finally dismiss any necessity for theory change. The problem of phenotypic complexity thus becomes (in)elegantly bypassed. Inevitably, the conclusion is reached that microevolutionary mechanisms are consistent with macroevolutionary phenomena [36], even though this has very little to do with the structure and predictions of the EES. The real issue is that genetic evolution alone has been found insufficient for an adequate causal explanation of all forms of phenotypic complexity, not only of something vaguely termed ‘macroevolution’. Hence, the micro–macro distinction only serves to obscure the important issues that emerge from the current challenges to the standard theory. It should not be used in discussion of the EES, which rarely makes any allusions to macroevolution, although it is sometimes forced to do so.

This a major concession on the part of a major figure in the world of evolution theory. It’s a huge black eye to the “All Is Well” crowd. Who will tell the media? Who will tell the Darwin enforcers? Who will tell the biology students, in high school or college, kept in the dark by rigid Darwinist pedagogy?

Evolution has only “strengths” and no “weaknesses,” you say? Darwinian theory is as firmly established as “gravity, heliocentrism, and the round shape of the earth“? Really? How can anyone possibly maintain as much given this clear statement, not from any ID advocate or Darwin skeptic, not from a so-called “creationist,” but from a central figure in evolutionary research, writing in a journal published by the august scientific society once presided over by Isaac Newton, for crying out loud?

To maintain at this point that “All Is Well” with evolution you have to be in a state of serious denial.

Photo credit: Charlesjsharp (Own work, from Sharp Photography) [CC BY-SA 4.0], via Wikimedia Commons.


Problem 6: Molecular Biology has Failed to Yield a Grand “Tree of Life”

When fossils failed to demonstrate that animals evolved from a common ancestor, evolutionary scientists turned to another type of evidence — DNA sequence data — to demonstrate a tree of life. In the 1960s, around the time the genetic code was first understood, biochemists Émile Zuckerkandl and Linus Pauling hypothesized that if DNA sequences could be used to produce evolutionary trees — trees which matched those based upon morphological or anatomical characteristics — this would furnish “the best available single proof of the reality of macro-evolution.” 99 Thus began a decades-long effort to sequence the genes of many organisms and construct “molecular” based evolutionary (“phylogenetic”) trees. The ultimate goal has been to construct a grand “tree of life,” showing how all living organisms are related through universal common ancestry.

The Main Assumption

The basic logic behind building molecular trees is relatively simple. First, investigators choose a gene, or a suite of genes, found across multiple organisms. Next, those genes are analyzed to determine their nucleotide sequences, so the gene sequences of various organisms can then be compared. Finally, an evolutionary tree is constructed based upon the principle that the more similar the nucleotide sequence, the more closely related the species. A paper in the journal Biological Theory puts it this way:

[M]olecular systematics is (largely) based on the assumption, first clearly articulated by Zuckerkandl and Pauling (1962), that degree of overall similarity reflects degree of relatedness. 100

This assumption is essentially an articulation of a major feature of the theory – the idea of universal common ancestry. Nonetheless, it’s important to realize that it is a mere assumption to claim that genetic similarities between different species necessarily result from common ancestry.

Operating strictly within a Darwinian paradigm, these assumptions flow naturally. As the aforementioned Biological Theory paper explains, the main assumption underlying molecular trees “derives from interpreting molecular similarity (or dissimilarity) between taxa in the context of a Darwinian model of continual and gradual change.” 101 So the theory is assumed to be true to construct a tree. But also, if Darwinian evolution is true, construction of trees using different sequences should reveal a reasonably consistent pattern across different genes or sequences.

This makes it all the more significant that efforts to build a grand “tree of life” using DNA or other biological sequence data have not conformed to expectations. The basic problem is that one gene gives one version of the tree of life, while another gene gives a highly different, and conflicting, version of the tree. For example, as we’ll discuss further below, the standard mammalian tree places humans more closely related to rodents than to elephants. But studies of a certain type of DNA called microRNA genes have suggested the opposite — that humans were closer to elephants than rodents. Such conflicts between gene-based trees are extremely common.

The genetic data is thus not painting a consistent picture of common ancestry, showing the assumptions behind tree-building commonly fail. This leads to justifiable questions about whether universal common ancestry is correct.

Conflicts in the Base of the Tree of Life

Problems first arose when molecular biologists sequenced genes from the three basic domains of life — bacteria, archaea, and eukarya — but those genes did not allow these basic groups of life to be resolved into a treelike pattern. In 2009, the journal New Scientist published a cover story titled, “Why Darwin was wrong about the tree of life” which explained these quandaries:

The problems began in the early 1990s when it became possible to sequence actual bacterial and archaeal genes rather than just RNA. Everybody expected these DNA sequences to confirm the RNA tree, and sometimes they did but, crucially, sometimes they did not. RNA, for example, might suggest that species A was more closely related to species B than species C, but a tree made from DNA would suggest the reverse. 102

This sort of data led biochemist W. Ford Doolittle to explain that “Molecular phylogenists will have failed to find the ‘true tree,’ not because their methods are inadequate or because they have chosen the wrong genes, but because the history of life cannot properly be represented as a tree.” 103 New Scientist put it this way: “For a long time the holy grail was to build a tree of life … But today the project lies in tatters, torn to pieces by an onslaught of negative evidence.” 104

Many evolutionists sometimes reply that these problems arise only when studying microorganisms like bacteria — organisms which can swap genes through a process called “horizontal gene transfer,” thereby muddying the signal of evolutionary relationships. But this objection isn’t quite true, since the tree of life is challenged even among higher organisms where such gene-swapping is not prevalent. Carl Woese, a pioneer of evolutionary molecular systematics, explains:

Phylogenetic incongruities can be seen everywhere in the universal tree, from its root to the major branchings within and among the various taxa to the makeup of the primary groupings themselves. 105

Likewise, the New Scientist article notes that “research suggests that the evolution of animals and plants isn’t exactly tree-like either.” 106 The article explains what happened when microbiologist Michael Syvanen tried to create a tree showing evolutionary relationships using 2000 genes from a diverse group of animals:

He failed. The problem was that different genes told contradictory evolutionary stories. … the genes were sending mixed signals. … Roughly 50 per cent of its genes have one evolutionary history and 50 per cent another. 107

The data were so difficult to resolve into a tree that Syvanen lamented, “We’ve just annihilated the tree of life.” 108 Many other papers in the technical literature recognize similar problems.

Conflicts Between Higher Branches

A 2009 paper in Trends in Ecology and Evolution notes that, “A major challenge for incorporating such large amounts of data into inference of species trees is that conflicting genealogical histories often exist in different genes throughout the genome.” 109 Similarly, a paper in Genome Research studied the DNA sequences in various animal groups and found that “different proteins generate different phylogenetic tree[s].” 110 A June, 2012 article in Nature reported that short strands of RNA called microRNAs “are tearing apart traditional ideas about the animal family tree.” Dartmouth biologist Kevin Peterson who studies microRNAs lamented, “I’ve looked at thousands of microRNA genes, and I can’t find a single example that would support the traditional tree.” According to the article, microRNAs yielded “a radically different diagram for mammals: one that aligns humans more closely with elephants than with rodents.” Peterson put it bluntly: “The microRNAs are totally unambiguous … they give a totally different tree from what everyone else wants.” 111

Conflicts Between Molecules and Morphology

Not all phylogenetic trees are constructed by comparing molecules like DNA from different species. Many trees are based upon comparing the form, structure, and body plan of different organisms — also called “morphology.” But conflicts between molecule-based trees and morphology-based trees are also common. A 2012 paper studying bat relationships made this clear, stating: “Incongruence between phylogenies derived from morphological versus molecular analyses, and between trees based on different subsets of molecular sequences has become pervasive as datasets have expanded rapidly in both characters and species.” 112 This is hardly the only study to encounter conflicts between DNA-based trees and trees based upon anatomical or morphological characteristics. Textbooks often claim common descent is supported using the example of a tree of animals based upon the enzyme cytochrome c which matches the traditional evolutionary tree based upon morphology. 113 However, textbooks rarely mention that the tree based upon a different enzyme, cytochrome b, sharply conflicts with the standard evolutionary tree. As one article in Trends in Ecology and Evolution observed:

[T]he mitochondrial cytochrome b gene implied . . . an absurd phylogeny of mammals, regardless of the method of tree construction. Cats and whales fell within primates, grouping with simians (monkeys and apes) and strepsirhines (lemurs, bush-babies and lorises) to the exclusion of tarsiers. Cytochrome b is probably the most commonly sequenced gene in vertebrates, making this surprising result even more disconcerting. 114

Strikingly, a different article in Trends in Ecology and Evolution concluded, “the wealth of competing morphological, as well as molecular proposals [of] the prevailing phylogenies of the mammalian orders would reduce [the mammalian tree] to an unresolved bush, the only consistent [evolutionary relationship] probably being the grouping of elephants and sea cows.” 115 Because of such conflicts, a major review article in Nature reported, “disparities between molecular and morphological trees” lead to “evolution wars” because “[e]volutionary trees constructed by studying biological molecules often don’t resemble those drawn up from morphology.” 116

Finally, a study published in Science in 2005 tried to use genes to reconstruct the relationships of the animal phyla, but concluded that “[d]espite the amount of data and breadth of taxa analyzed, relationships among most [animal] phyla remained unresolved.” The following year, the same authors published a scientific paper titled, “Bushes in the Tree of Life,” which offered striking conclusions. The authors acknowledge that “a large fraction of single genes produce phylogenies of poor quality,” observing that one study “omitted 35% of single genes from their data matrix, because those genes produced phylogenies at odds with conventional wisdom.” The paper suggests that “certain critical parts of the [tree of life] may be difficult to resolve, regardless of the quantity of conventional data available.” The paper even contends that “[t]he recurring discovery of persistently unresolved clades (bushes) should force a re-evaluation of several widely held assumptions of molecular systematics.” 117

Unfortunately, one assumption that these evolutionary biologists aren’t willing to re-evaluate is the assumption that universal common ancestry is correct. They appeal to a myriad of ad hoc arguments — horizontal gene transfer, long branch attraction, rapid evolution, different rates of evolution, coalescent theory, incomplete sampling, flawed methodology, and convergent evolution — to explain away inconvenient data which doesn’t fit the coveted treelike pattern. As a 2012 paper stated, “phylogenetic conflict is common, and frequently the norm rather than the exception.” 118 At the end of the day, the dream that DNA sequence data would fit into a nice-neat tree of life has failed, and with it a key prediction of neo-Darwinian theory.


The Origin and Evolution of Man | Biology

In this article we will discuss about:- 1. Introduction to Origin of Man 2. Features of Man 3. History 4. Miscellaneous Remains 5. Biological Trends 6. General Consideration.

  1. Introduction to Origin of Man
  2. Features of Man
  3. History of Mankind
  4. Miscellaneous Remains of Man
  5. Biological Trends in Human Evolution
  6. General Consideration on Human Ancestry

1. Introduction to Origin of Man:

The origin and evolution of man, Homo sapiens, have been a topic of great biolo­gical interest since time immemorial. The idea that man is a creation of a super­natural power prevailed for long time in earlier days.

But the Biologists view the origin of man using knowledge on mor­phology, physiology, embryology and fossil records. Man evolved from some unknown mammalian ancestor and reached the pin­nacle of evolutionary fabric.

Man is placed under the family Hominidae of the order Primate and differs from other anthropoid apes by having: Large size of brain with greater functional ability (Maximum in Gorilla = 650 c.c., Minimum in Man = 1000 c.c.) The brain case is larger than face region.

The face is flatter with less protruding lower jaw. Continuous growth of long hair on head which are spare and short on body. Generalized hands with better developed thumbs and long leg with non-opposable big toe. Man is terrestrial in habit and walks erect on two feet. They surpass all other animals by possessing the ‘human features’ which are exclusive for them.

2. Features of Man:

In contrast to that of the anthropoids, the human line showed a large number of progressive features.

The features are:

(a) The face becomes flattened and is devoid of a nuzzle (Fig. 1.27).

(b) The brow ridges gradually decline and disappear.

(c) The cranium rises sufficiently above the orbits to house a larger brain.

(d) The skull is rounded at the rear.

(e) The foramen magnum and occipital condyles are shifted ventrally to join with the upright vertebral column.

(f) A mastoid process arises in the ear region.

(g) The teeth become smaller in size and are arranged in a U-shaped arc. The canines are moderate in size.

(h) The arms with the fingers are proportionately shorter. The feet are nongrasping. The toes are placed in line. The heal bone is elongated to help insertion of muscles in upright posture and walking.

(i) The vertebral column shows slight curvature.

(j) The ilia are wider than length. Broader ilia help insertion of the big gluteal mus­cles which is involved in balance.

The great apes can make sounds which indicate some desires and emotions but fail to describe-objects. But man can deve­lop sounds into words symbolising things or ideas. The ape-prehuman transition is associated with the descent from trees to the ground which is of great significance in human evolution. This transition freed the hands for making and use of tools to supplement the action of the hands.

3. History of Mankind:

Before the practice of burial of the dead, remains of early man were limited to member of skulls (often partial) and some other bony remains. Remains of complete skeleton became more numerous when the practice of burial of the dead was followed.

The work of prehistoric man gave ample materials to draw an inference regarding the activities and manner of life. Limita­tions in material of early man make the direct line of descent more confusing.

The time and place when modern man first originated are controversial. The earliest anthropoids, Parapithecus, Propliopithecus, etc., (represented by the remains of jaws) were discovered from the Oligocene bed of Egypt.

During Miocene period the fossils of anthropoids showed considerable diver­sity, some possessing prehuman features may have evolved into human line and others leading toward the great apes. An anthropoid fossil, Dryopithecus is re­garded to stand close to the point of divergence.

Primitive Hominids:

Discoveries of remains of prehistoric species and races will give an idea of human evolution. The major forms, as re­corded uptil date, are as follows (Fig. 1.28).

Australopithecus, Zinjanthropus, etc., represent the primitive Hominids:

The remains of these hominids (Austra­lopithecus, Zinjanthropus, etc.) were disco­vered in Mid-Pleistocene or earlier in Transvaal, South Africa in 1925 and in Olduvai Gorge Tanganyika in 1959. Many skulls and some skeletal parts have been discovered.

The characteristics are:

(a) The skull was smaller in size than that of modern man.

(b) The volume of brain ranged from 600-700 c.c.

(c) The face was protruding and the forehead was higher than that in apes.

(d) The brow ridges were pro­minent.

(e) The occipital condyles were ventrally placed and the rear part of the skull was rounded.

(f) The jaws were large with small incisors, large and spatu- late canines, large cheek teeth.

(g) The ilia of pelvis were wider and the limb bones were slender.

(h) The total height was about 5 feet. They used simple chipped pebble tools.

Pithecanthropus erectus—Java man:

Fragmentary remains of Pithecanthropus erectus were discovered in Mid-Pleistocene of Solo River near Trimil, Java since 1891 up to 1945.

The characteristic features are:

(a) The skull was flattish-topped and projected behind.

(b) The brow ridges were solid above the orbits.

(c) The brain volume was 775-900 c.c. The imprint of brain possibly indicated the ability of speech.

(d) The jaws were protruding.

(e) The teeth were arranged in even curve but the canines were projecting.

(f) The femur reflected its upright posture.

(g) The height was about 5 feet. No associated tools were found.

Pithecanthropus (Sinanthropus) pekinensis —Peking man:

The remains of skulls and parts, jaws with teeth and some limb bones of Pithecanthropus (Sinanthropus) pekinensis were discovered up to 1943 from the Mid-Pleis­tocene caves at Choukoutien (South-west of Peking), China.

The noted features are:

(a) The skull was small and the brain volume was 850-1300 c.c.

(b) The skull was low-vaulted.

(c) The brow ridges were stout.

(d) The imprint of brain sug­gested the ability of speech.

Various implements of quartz and other rocks were discovered. The hearths showed the use of fire.

Homo habilis—Transitional man:

The remains of this species were dis­covered in Pleistocene bed in East Africa. They were the makers of crudely chipped stone tools. They represent an intermediate stage between the Australopithecus and Pithecanthropus erectus. The mean capacity of brain was 680 c.c.

Homo heidelbergensis—Heidelberg man:

One lower jaw of Homo heidelbergensis was discovered in 1907 in sand pit at Mauer near Heidelberg (Germany). The remains were of Mid-Pleistocene period. The jaw was massive with very broad ascending ramus indicating powerful jaw muscles. There was no chin. The teeth were stout and the canines were not enlarged. Asso­ciated tools were not found.

Homo neanderthalensis—Neanderthal man:

The remains of Homo neanderthalensis to­talling well over one hundred individuals were discovered from the late Pleistocene bed (before or during first Ice Age) in Spain and North Africa to Ethiopia, Mesopotamia. Southern Russia, Gilbraltar, Neanderthal Valley near Dusseldorf (Ger­many) from 1848-1861.

The Neanderthal man had:

(a) massive long and flat-topped skull.

(b) The forehead was receding.

(c) The brow ridges were heavy.

(f) The average brain volume was 1450 c.c.

(g) The jaws were protruding but the chin was receding.

(i) The attachment sites of occipital region of skull and the cervical vertebrae indi­cated the existence of powerful neck mus­cles.

(j) The limb bones were heavy and slightly curved.

(k) The height of males was about 5 feet 3-5 inches.

The females were shorter than males. The Neanderthal man used to live in caves and rock shelters with stone stools and weapons. There was evidence of use of fire. The estimated age was about 100,000 years.

Homo sapiens – Cro- Magnon man:

The remains of Cro-Magnon man of estimated age about 30,000-13,000 b.c. were found in late Pleistocene (close of last Ice Age and later) bed of France to Czechoslovakia, East Africa and Eastern Asia.

The distinguishing features are:

(a) The skull was long and high with no brow ridges.

(b) The face resembled the modern man.

(c) The occipital region of skull was rounded.

(d) The chin was well developed.

(e) The average brain volume was about 1590 c.c.

(f) The height of males was about 5 feet 10 inches.

They were cave-dweller. They had stone implements and they could make wall paintings and sculpture.

4. Miscellaneous Remains of Man:

Three jaws and skull fragment of Ternifine man were found in Ternifine and Casablanca, North Africa in 1952. These Mid-Pleistocene re­mains resembled Heidelberg and Peking materials.

Remains of 13 individuals including complete skeleton were discovered in Mount Carmel, Palestine (Israel). These upper Pleistocene remains showed characteristics of both Neanderthal and modern man, but slightly taller.

The remains (occi­pital and parietal bones) were found in Swanscombe, Kent, England in 1936- 1937. They were of Mid-Pleistocene age. The bones were thick and the brain vo­lume was estimated to be about 1300 c.c.

(D) Solo man (Homo soloensis):

The remains of eleven partial skulls and two femurs of Pleistocene age were discovered from Solo River near Ngandong, Java in 1933. They had low forehead and heavy brow ridges. They exhibited many features which were more modern.

(E) Rhodesian man (Homo rhodesiensis):

The remains of Rhodesian man of late Pleistocene age were found in 1921 at Broken Hill, Rhodesia (South Africa). A similar skull was also discovered in 1953 in Capetown. The remains consisted of one skull, upper jaw, parts of limb bones, pelvis, sacrum, etc. The brain volume was about 1300 c.c. The characteristics of face, brow ridges, orbits, palate and limb bones were much like those of modern man.

The other fragmen­tary remains of man include that of:

(i) skull fragments of Pithecanthropus robustus from Java (1938)

(ii) portions of a huge jaw of Meganthropus palaeojavanicus from Java (1941) and

(iii) three huge molars (five to six times the bulk of those of the present day’s man) of Gigantopilhecus blacki in 1935-1939.

These molars were possibly collected from caves in South China.

5. Biological Trends in Human Evolution:

The evolution of man involves the following significant changes:

(a) Switch over from the four gait apes to the bipedal gait of man.

(b) Perfection of hand for tool making.

(c) Increase of intelligence and size of brain.

(d) Change of diet from fruits, hard nuts, hard roots to softer foods.

(e) Increase in their ability to commu­nicate with others and development of community behaviour.

6. General Consideration on Human Ancestry:

Since the discovery of the ‘missing link’ between apes and men in 1894 by a Dutch anatomist, E. Dubois, a large num­ber of fossils of man have been brought to the limelight. All the newer finds as well as the older ones are being interpreted by different authorities in different ways. The scientists of the past described the fossils in terms of ‘individual types’ rather than ‘populations’.

They gave a scientific name of their new find and placed it in a sepa­rate species and in a separate genus, when­ever applicable. But the modern Anthro­pologists and Zoologists are trying hard to discard nearly all the names of ‘genera’ which were coined in the past.

They recognise that the ancestors of man have progressed mainly along a single evolu­tionary line and at times this line became branched -to give two or three related species (Fig. 1.29). During the past 600,000 years it consisted of a single species having a common gene pool with a number of races.

The remains of ‘Southern apes’ (Austra­lopithecus) have been claimed to be fore­runners of man. These creatures were more like apes than man in respect of their intelligence and way of life. They could walk erect and the architecture of limb and body skeleton was much like those of modern man.

An intermediate fossil form, Homo habilis, an intermediate form between Australopithecus and the ancient species of man (Java and Peking man), was discovered from the same bed containing East African Australopithecus.

This fact gave evidence that the Australopi­thecus was the direct ancestor of man and they persisted side by side with their derivatives—the earliest men. The transi­tion from apes to man was a gradual process and the series of fossils portrays a gradual but complete transition from apes to modern man.

Comparative studies on morphology and chemistry of protein have proved that Homo sapiens, gorilla and chimpanzee arc closely related to each other than other anthropoid apes like orangutan and gibbon.

Homo sapient, gorilla and chimpanzee have possibly, evolved from a group of apes common in Eurasia and Africa during Miocene. The immediate ancestor of Homo, as stated earlier, was the Australopithecus which lived between Pliocene to Pleistocene in North Africa and Eurasia.

The earliest man, Pithecanthropus erectus, was widespread in Eurasia during Pleistocene possibly evol­ved into modern man by series of gradual stages without splitting into separate spe­cies (Fig. 1.30). The main characteristics which differentiate man from apes evolved at different rates.

The use of tools appears to have evolved first which preceded the increase of size of brain. Both these were accompanied by the change from four- footed gait to bipedal erect posture.


Evolution Is Ongoing

Humans continue to evolve as a species. Blue eyes came about just 10,000 years ago when a gene mutation turned off the switch to produce brown eyes. Other relatively recent mutations include an ability to digest milk. The process of natural selection and survival of the fittest may have a more limited effect on modern human evolution, however.

Advances in modern medicine make it possible to survive diseases that would have once proved fatal. Many people are having babies when they are older, when the risks of genetic diseases may be greater. The theory of evolution holds that life will continue to diversify and adapt to changing conditions.


Watch the video: Grade 12 Life Sciences Evolution Part 1 (December 2021).