Population where most of the newborns die soon?

Is there an ecological name to describe a population of organisms where most of the newborns die after birth without reproducing? The population as a whole keeps growing, however, because there are enough individuals that manage to reproduce.

Yes, we talk about r/K selection theory:

In ecology, r/K selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring. The focus upon either increased quantity of offspring at the expense of individual parental investment of r-strategists, or reduced quantity of offspring with a corresponding increased parental investment of K-strategists, varies widely, seemingly to promote success in particular environments.

The type of species you describe are the r type.

Please note the following potential confusions:

A species can vary its strategy through time and space

Species can change from K to r (and vice-versa) depending on the environment and number of individuals. Consider humans as an example.

The expression r/K selection theory can be misleading

The term "selection" in "r/K selection theory" can be a bit misleading as it refers more to a demographic reality (which has come to be due to selection pressures) but not to the selection process behind it.

Alternative meaning of 'r/K selection theory'

The termsrandKare sometimes used to mean whether a species has reached carrying capacity (K) or whether they are growing in number (r) which is not exactly the same as the interpretation of whether there is much parental investment in the species presented in the wikipedia article.

This second interpretation is actually closer to the origin of the terms r and K. The most common (and one of the simplest) equation of population growth through time is the logistic equation (see here for an easy explanation and also wiki > Population ecology )

$$frac{dN}{dt} = rN left( 1 - frac{K}{N} ight) $$

, where $N$ is the population size, $t$ is time in generation, $r$ is the maximal growth rate and $K$ is the carrying capacity. On the graph above, $r$ represent the maximal slope (that is the maximal growth rate).

r selected species are those that have a growth rate as indicated at the center of the graph. K selected species are those that have a growth rate of 1 (no increase in $N$) as the ones that are at carrying capacity $K$.

Why is infant mortality higher in boys than in girls? A new hypothesis based on preconception environment and evidence from a large sample of twins

Infant mortality is higher in boys than girls in most parts of the world. This has been explained by sex differences in genetic and biological makeup, with boys being biologically weaker and more susceptible to diseases and premature death. At the same time, recent studies have found that numerous preconception or prenatal environmental factors affect the probability of a baby being conceived male or female. I propose that these environmental factors also explain sex differences in mortality. I contribute a new methodology of distinguishing between child biology and preconception environment by comparing male-female differences in mortality across opposite-sex twins, same-sex twins, and all twins. Using a large sample of twins from sub-Saharan Africa, I find that both preconception environment and child biology increase the mortality of male infants, but the effect of biology is substantially smaller than the literature suggests. I also estimate the interacting effects of biology with some intrauterine and external environmental factors, including birth order within a twin pair, social status, and climate. I find that a twin is more likely to be male if he is the firstborn, born to an educated mother, or born in certain climatic conditions. Male firstborns are more likely to survive than female firstborns, but only during the neonatal period. Finally, mortality is not affected by the interactions between biology and climate or between biology and social status.

For U.S. Children, Minorities Will Be The Majority By 2020, Census Says

America is heading toward the day when whites will no longer make up the majority of the population. And U.S. children will get there soon, according to a new U.S. Census Bureau report. The agency also says the overall U.S. population will grow older — and grow more slowly — in coming years.

By around 2020, "more than half of the nation's children are expected to be part of a minority race or ethnic group," the Census Bureau says, putting Americans under the age of 18 at the front of a trend that will see the overall population follow suit some 20 years later.

"When that shift for the U.S. as a whole takes place by 2044, the Census Bureau predicts no one racial or ethnic group will dominate the U.S. in terms of size," NPR's Hansi Lo Wang reports. "Overall, the U.S. population is set to grow more slowly over the next few decades partly because of declining fertility rates. It's expected to hit 400 million by 2051."

The forecast lists several changes America will undergo in the next 45 years.

Another finding states that from 2014 to 2060, "the working-age population is projected to decrease from 62 percent to 57 percent of the total population."

Why does preterm birth happen?

Preterm birth occurs for a variety of reasons. Most preterm births happen spontaneously, but some are due to early induction of labour or caesarean birth, whether for medical or non-medical reasons.

Common causes of preterm birth include multiple pregnancies, infections and chronic conditions such as diabetes and high blood pressure however, often no cause is identified. There could also be a genetic influence. Better understanding of the causes and mechanisms will advance the development of solutions to prevent preterm birth.

With 250 babies born each minute, how many people can the Earth sustain?

We don’t know for sure as all figures are estimates, but UN data suggests there were about a billion people in 1800, 2 billion in 1927, 5 billion in 1987 and just over 7.5 billion today.

There are on average about 250 babies born every minute – more than 130 million in a year. It is projected that there will be 11 billion people by 2100. New UN figures are due out in June.

Most national governments make their own population projections. The United Nations and the World Bank figures are the most widely used globally.

Since the 1960s, more boys than girls have been born every year. About 117 million women are believed to be “missing” in Asia and eastern Europe – due to discriminatory son preference and gender-biased sex selection.

Over the last 30 years, some regions have seen up to 25% more male births than female births, reflecting the persistent low status of women and girls. The consequent gender imbalance can have damaging social effects such as increased sexual violence and trafficking.

Where is the population rising fastest – and slowest?

Broadly speaking, the fastest population rises are being recorded in Africa and Asia, which will have 15 of the 20 most populous nations by 2050. By that year, there will be more Nigerians than Americans. By 2100, it is projected that as many as one-third of all people – almost 4 billion – will be African.

At the other end of the scale, population growth has stalled – or even gone into reverse – in parts of western Europe, Japan and Russia.

Are these numbers sustainable?

A nuanced question. Experts like Paul Ehrlich argue that the population of the world has long since surpassed optimal levels, though critics counter that consumption is as important as population levels.

Some believe the very argument about overpopulation is controversial as it tends to point the finger at poorer parts of the world with large growth rates, and not at richer regions, which use disproportionately high amounts of resources.

What influences fertility?

The fertility rate is the number of children born for every woman of childbearing age in a population. The things that tend to affect it include female empowerment, wellbeing and the status of children, technological and economic changes, and opportunities for family planning.

The level of education in a society – of women in particular – is one of the most important predictors for the number of children families have.

The global average fertility rate is just below 2.5 children per woman today. Over the last 50 years the global fertility rate has halved, as some of these factors bore down on family sizes.

In the pre-modern era, fertility rates of 4.5 to 7 children per woman were common. At that time, high mortality rates of young people kept population growth low. As health improved, the population growth rate began to soar, only flattening out as the fertility rate declined towards 2 children per woman.

A record number of women now use contraception. Figures from the UN’s Department of Economic and Social Affairs show 64% of married and cohabiting women used modern or traditional methods of contraception in 2015 – a significant rise from 36% in 1970. But the figures show wide disparities between and within regions and countries.

Africa has the lowest percentage of women using contraceptives, and the highest unmet need in the world. Despite this, some African countries have made the biggest leaps in contraception use over the past 40 years and are projected to make the greatest gains in the next 15.

In Mauritius, rapid population growth in the early 60s led the government to launch a family planning programme, and the country now boasts the highest rates (75.5%) on the continent.

If birthrates have fallen so far, why is the population still rising fast?

Of course, fertility rates are just half the story. People are living longer – far longer in some parts of the world. About 55m people die every year, which is less than half the number who are born.

The number of children who die before reaching their fifth birthday has fallen to an all-time low: it is currently less than half what it was in 1990.

A child’s chance of survival is still vastly different depending on where they are born.

Sub-Saharan Africa has the highest under-five mortality rate – 79 deaths for every 1,000 births, which means that one child in 13 die before their fifth birthday. This compares with six for every 1,000 in Europe and northern America and four for every 1,000 in Australia and New Zealand.

At the same time, life expectancy is higher than 80 in 30 countries and higher than 70 in more than 100 countries.

So what is the demographic dividend?

Countries that do succeed in reducing fertility rates can benefit from a demographic dividend, where there are more people in work than children to support.

Where you have a rapid decline in fertility, the younger population is no longer growing as fast and the economy should receive a boost because the number of workers per child increases, and that should provide a period of rapid economic growth. This was the experience in the east Asian “tiger” countries like South Korea and Taiwan in the 70s. Now countries such as China and India are benefiting from a demographic dividend.

A consequence of falling child mortality but continuing high fertility is a “youth bulge” – a high population of young people. In Africa, because rising numbers of increasingly educated people have not been matched by jobs, this has led to significant youth unemployment.

A young population offers a lot of potential for the development of a country, but only if their talents are realised through investment. If there is little support given to young people to develop the skills they need as they enter the labour market, then the economy misses out.

Isn’t it problematic that western populations are declining?

Another global demographic shift is ageing populations in developed countries such as Japan and Germany, and also in advanced developing countries. In nations as diverse as Bangladesh, Cambodia, Mongolia and Vietnam, the population aged over 60 will triple by 2050.

This year, the number of people worldwide who are over 60 will rise above 1 billion for the first time. By 2050, it is forecast to be 2 billion. This raises the question: who will pay for them?

Falling birth rates can mean fewer young workers entering the labour force at a time when the healthcare and social support costs associated with ageing are likely to rise.

But ageing populations can be a cause for celebration. It means development has taken place.

If countries plan for the shift they can see gains. In Japan, for example, the introduction of universal health coverage meant more treatment for high blood pressure, and therefore fewer strokes, extending worker productivity.

If countries consider redesigning pension systems and offering flexible work in retirement, seeing older volunteers as a potential resource, then many more mature members of society can have not just greater life expectancy but also be healthier for longer.

Later retirement does not have to mean fewer jobs for the young. More older people working can increase GDP and generate more demand for young workers.

The funding battles over international family planning are ongoing. US Congress rejected the 2018 budget. The debates will continue in 2019.

Family planning organisations are learning that to survive political shifts and budget cuts, they need to diversify their sources of funding. This means seeing family planning as not just a public health concern but also about development and a clear return on investment.

Where women have control over their own fertility, there are gains well beyond their own families.

Further reading the world population project by World Data Lab

Family Planning 2020 (FP2020): a global partnership that supports the rights of women and girls to decide whether, when, and how many children they want to have.

Population matters: on working towards a sustainable future.

She decides: a global movement to promote, provide and protect the fundamental rights of woman and girls.

Kaiser Family Foundation: on global health policy, especially their research on the impact of the “global gag rule”.

The Bill and Melinda Gates Institute for Population and Reproductive Health at the Johns Hopkins Bloomberg School of Public Health.

Long-Awaited Baby Boomer Die-Off To Begin Soon, Experts Say

WASHINGTON, DC—After decades of waiting, the much-anticipated mass Baby Boomer die-off should finally commence within the next five to ten years, Census Bureau officials said Monday.

"I am pleased to announce that it won't be much longer now," Census Bureau deputy director Arthur Clausewitz said at a press conference. "According to our statistics, by 2009, we should see the Baby Boomers start to die off in large numbers. Heart attacks, strokes, cancer, kidney failure—you name it, the Boomers are going to be dropping from it."

Clausewitz said the Great Boomer Die-Off should hit full stride in approximately 2015, when the oldest members of the Baby Boom generation—born during the last days of World War II—turn 70.

"Before long, tens of millions of members of this irritating generation will achieve what such Boomer icons as Jim Morrison, Janis Joplin, Timothy Leary and John Kennedy already have: death. Before long, we will live in a glorious new world in which no one will ever again have to endure tales of Joan Baez's performance at Woodstock."

Despite his enthusiasm, Clausewitz cautioned that the Great Boomer Die-Off will not be without its downside.

"Our nation must steel itself for one vast, final orgy of Boomer self-obsession as we are hit with a bewildering onslaught of magazine pictorials, hardcover coffee-table books and multi-part, Motown-soundtracked television specials looking back on the glory days of the 1960s," Clausewitz said. "But once this great, final spasm of nostalgia passes, the ravages of age will take its toll on boomer self-indulgence, and the curtain will at long last fall on what is regarded by many as the most odious generation America has ever produced."

Clausewitz also noted that the cost of caring for the elderly and infirm of the nation's largest demographic group will be enormous.

"The selfishness that has been a hallmark of the Boomers will continue right up to the very end, as they force millions of younger Americans to devote an inordinate amount of time and resources to their care, bankrupting the Social Security system in the process," Clausewitz said. "In their old age, the Boomers will actually manage to take as much from the next generation as they did the previous one, which fought WWII so that their Boomer children could have Philco TVs and Davy Crockett air rifles."

The Great Boomer Die-Off will have its greatest impact, experts say, in the economic sector. The funeral industry is expected to enjoy a $700 million surge in profits, a result of the inevitable onslaught of lavish, Big Chill-themed memorial services. Many industries, however, will likely suffer from the die-off, including the manufacturers of sport-utility vehicles, home jacuzzis and hair-replacement systems. The financial sector will also feel the hit, as it is forced to fill some 400,000 high-paying stockbroker and corporate-banking jobs, held for decades by ex-hippies.

"It's not exactly clear how, but for the past 40 years, this generation has managed to keep the spotlight on itself," Brown University history professor A. Thomas Raymond said. "The era-defining flower children of the ❠s, hedonistic disco-goers of the ❰s, BMW-driving yuppies of the ➀s and graying private-investor homeowner parents of the ➐s all have one thing in common: They're all Boomers."

"It takes a staggering amount of effort to keep oneself the focus of an entire society for one decade, much less four, but the Boomers somehow pulled it off," Raymond continued. "Thankfully, though, their reign will soon come to an end. It's just too bad so few of them died before they got old."

Scientists: ‘Look, One-Third Of The Human Race Has To Die For Civilization To Be Sustainable, So How Do We Want To Do This?’

WASHINGTON—Saying there’s no way around it at this point, a coalition of scientists announced Thursday that one-third of the world population must die to prevent wide-scale depletion of the planet’s resources—and that humankind needs to figure out immediately how it wants to go about killing off more than 2 billion members of its species.

Representing multiple fields of study, including ecology, agriculture, biology, and economics, the researchers told reporters that facts are facts: Humanity has far exceeded its sustainable population size, so either one in three humans can choose how they want to die themselves, or there can be some sort of government-mandated liquidation program—but either way, people have to start dying.

And soon, the scientists confirmed.

“I’m just going to level with you—the earth’s carrying capacity will no longer be able to keep up with population growth, and civilization will end unless large swaths of human beings are killed, so the question is: How do we want to do this?” Cambridge University ecologist Dr. Edwin Peters said. “Do we want to give everyone a number and implement a death lottery system? Incinerate the nation’s children? Kill off an entire race of people? Give everyone a shotgun and let them sort it out themselves?”

“Completely up to you,” he added, explaining he and his colleagues were “open to whatever.” “Unfortunately, we are well past the point of controlling overpopulation through education, birth control, and the empowerment of women. In fact, we should probably kill 300 million women right off the bat.”

Because the world’s population may double by the end of the century, an outcome that would lead to a considerable decrease in the availability of food, land, and water, researchers said that, bottom line, it would be helpful if a lot of people chose to die willingly, the advantage being that these volunteers could decide for themselves whether they wished to die slowly, quickly, painfully, or peacefully.

Additionally, the scientists noted that in order to stop the destruction of global environmental systems in heavily populated regions, there’s no avoiding the reality that half the world’s progeny will have to be sterilized.

“The longer we wait, the higher the number of people who will have to die, so we might as well just get it over with,” said Dr. Chelsea Klepper, head of agricultural studies at Purdue Univer­sity, and the leading proponent of a worldwide death day in which 2.3 billion people would kill themselves en masse at the exact same time. “At this point, it’s merely a question of coordination. If we can get the populations of New York City, Los Angeles, Beijing, India, Europe, and Latin America to voluntarily off themselves at 6 p.m. EST on June 1, we can kill the people that need to be killed and the planet can finally start renewing its resources.”

Thus far, humanity has been presented with a great variety of death options, among them, poisoning the world’s water supply with cadmium, picking one person per household to be killed in the privacy of his or her home, mass beheadings, and gathering 2.3 billion people all in one place and obliterating them with a single hydrogen bomb.

Sources confirmed that if a death solution is not in place by Mar. 31, the U.N., in the interest of preserving the human race, will mobilize its peacekeeping forces and gun down as many people as necessary.

“I don’t care how it happens, but a ton of Africans have to go, because by 2025, there’s no way that continent will be able to feed itself,” said Dr. Henry Craig of the Population Research Institute. “And by my estimation, three babies have to die for every septuagenarian, because their longer life expectancy means babies have the potential to release far more greenhouse gases going forward.”

While the majority of the world’s populace reportedly understands this is the only option left to save civilization, not all members of the human race are eager to die.

“I personally would rather live, but taking the long view, I can see how ensuring the survival of humanity is best,” said Norwich, CT resident and father of three Jason Atkins. “I guess if we were to do it over again, it would make sense to do a better job conserving the earth’s finite resources.”

“Hopefully, the people who remain on the planet will use the mass slaughter of their friends and loved ones as an incentive to be more responsible going forward,” he added.

Natural Selection

Natural selection occurs when there are differences in fitness among members of a population. As a result, some individuals pass more genes to the next generation. This causesallele frequencies to change.

Sickle Cell and Natural Selection

The example of sickle-cell anemia is described in the Figure below and Table below. It shows how natural selection can keep a harmful allele in a gene pool. You can also watch a video about natural selection and sickle-cell anemia at this link:

Sickle Cell and Natural Selection. Notice the normal-shaped red blood cell on the left, and the sickle-shaped cell on the right.

Genotype Phenotype Fitness
AA 100% normal hemoglobin Somewhat reduced fitness because of no resistance to malaria
AS Enough normal hemoglobin to prevent sickle-cell anemia Highest fitness because of resistance to malaria
SS 100% abnormal hemoglobin, causing sickle-cell anemia Greatly reduced fitness because of sickle-cell anemia

Here&rsquos how natural selection can keep a harmful allele in a gene pool:

  • The allele (S) for sickle-cell anemia is a harmful autosomal recessive. It is caused by a mutation in the normal allele (A) for hemoglobin (a protein on red blood cells).
  • Malaria is a deadly tropical disease. It is common in many African populations.
  • Heterozygotes (AS) with the sickle-cell allele are resistant to malaria. Therefore, they are more likely to survive and reproduce. This keeps the S allele in the gene pool.

The sickle-cell example shows that fitness depends on phenotypes. It also shows that fitness may depend on the environment. What do you think might happen if malaria was eliminated in an African population with a relatively high frequency of the S allele? How might the fitness of the different genotypes change? How might this affect the frequency of the S allele?

Natural Selection and Polygenic Traits

Sickle-cell trait is controlled by a single gene. Natural selection for polygenic traits is more complex, unless you just look at phenotypes. Three ways that natural selection can affect phenotypes are shown in Figure below. You can also watch an animation comparing the three ways at the link below. hp23/2301s.swf.

  1. Stabilizing selection occurs when phenotypes at both extremes of the phenotypic distribution are selected against. This narrows the range of variation. An example is human birth weight. Babies that are very large or very small at birth are less likely to survive. This keeps birth weight within a relatively narrow range.
  2. Directional selection occurs when one of two extreme phenotypes is selected for. This shifts the distribution toward that extreme. This is the type of natural selection that the Grants observed in the beak size of Galápagos finches.
  3. Disruptive selection occurs when phenotypes in the middle of the range are selected against. This results in two overlapping phenotypes, one at each end of the distribution. An example is sexual dimorphism. This refers to differences between the phenotypes of males and females of the same species. In humans, for example, males and females have different heights and body shapes.

Natural selection may affect the distribution of a polygenic trait. These graphs show three ways this can happen.

9 Answers 9

The first to smell something fishy will probably be those who are caring a newborn who happened to be born shortly before the impact.

With no age progress the baby will not gain weight, will not stop looking like a wrinkled potato, will not get out of the 3 hours eat-sleep-poop cycle.

The pediatrics following these babies will notice that it's not just a single occurrence but a systematic event. From there observation will extend to children and adults.

For the first observations on babies to happen I think it will be a matter of one-two weeks.

Aging and death

I'll use ageing as the process of the damage we accumulate over time from normal growth.

When we don't age, it'll be difficult to see for most. Ageing is a slow and often unpredictable process. Our stamina decreasing, dementia or just our skin wrinkling are thing we would only notice over longer periods and not day to day. You can easily attribute ageing changes that are day to day to your daily routine or just to your mood, as you see things differently day to day. After you slept bad you might look into the mirror and see an old wrinkly thing staring back, while the next day you see a still young person still able to make a difference.

There are however times it is more noticeable. Especially at the latest (terminal) stages of ageing it can be easily visible from day to day. Think dementia, failing hearts or failing immune systems. Some might still die, as the heart failure can still occur over time without further ageing, but a lot of others will stay alive. This is the first indication we've stopped ageing. From one source on the internet about 100.000 people die from age related causes. With such a large population, we would find large deviations from people not ageing really quickly. Although the first day it might be seen as a curious thing to investigate, from day two we would put more effort into it. By day three we would probably know something weird is happening.

How quickly we would find out it's ageing that stopped is a difficult question. Maybe we notice in the cultures we make to see (ab)normal growth in cells that they don't age any more. The theories might come quick, but evidence will take a while for us to empirically prove it.

A rough estimate would be between a month and half a year for the scientific community to come to this conclusion more or less unanimously.

So. when does life begin anyway?

So to answer your question we need to know when life begins. Given pro-choice vs anti-abortion debates this is not clear and resolved with any consensus. I'm giving 3 answers depending on when you decide life begins. Does it begin

  • at sperm and egg?
  • at conception?
  • at birth?
  • at age 12 when telomeres start to shrink?

The answers for the last 2 are the same.

Fertility lab techs (next day), supermarket inventory managers (within a week), women trying to buy pregnancy tests (within a week).

In one extreme interpretation (ova and sperm are alive), all periods may stop (depending on how alive an ova in an ovary is considered), and all sperm are immature, so the first to notice will be Male fertility clinics, after every test returns failure for the same reason - underdeveloped, or missing, sperm.

Periods stop globally, and that's notable to each individual woman, but before that's correlated inventory managers will notice that pads and tampons are no longer selling from supermarkets. These have a steady predictable rate of sale so it will be extremely suspicious when they're not moving.

Pregnancy tests will be sold out planet wide within a few days too.

Women who are 8.99 months pregnant, and retrenched maternity staff (within a week)

If life begins at conception, all embryos and fetuses will stop developing - because they're alive.

I'm greatly simplifying childbirth here, but if a baby is expected to be due in the next week, and it never finishes aging to the point that it's ready, I'd say it's very suspicious. Expectant mothers are going to held in suspense as their immortal fetus settles in for the long haul.

Birthing suites are expensive, there'll be scheduled c sections pre booked, and some will be induced chemically, but if they're still idle for a few days, or everyone is getting induced, that will raise some questions.

Or scientists working with surprisingly eternal shrews. (Within 6 weeks)

If due to magic the wave can differentiate between fetus and born, or you declare life begins at birth, then newborns will stop developing. This could take first time parents unfamiliar with what to expect a few months to realize, especially if behavior changes still occur from learning. (Repeat parents may get suspicious after a few weeks). I suspect parents taking infants a few months old to the doctor afraid their not gaining weight will be the first clue we have about it in humans.

If, as your recent comment implies, for the purpose of anti-aging ray life doesn't start until age 12, then adolescents will get stuck in early puberty. That sounds horrible, and may take a year to recognize or more, but there's a faster way if we go to non human mammals.

Your wave only affects mammals, and these mammals have a life span of about 6 months.

Any immortal affect is 100 times more noticeable on these than on humans. The scientists who are running tests on shrews and are waiting for some notable event in their development (puberty, death, litter, etc.) will be held in suspense until they start investigating.

I assume that with “don’t age anymore” you mean that mammals would still grow up into full adulthood but don’t start (or continue) the long decline and decay into old age, right? So at some point (after all biologically old humans have died of various causes) all humans who aren’t still growing up would look like

In that case I think we’d first notice it in short-lived mammals like mice or rats which often have a lifespan of less than 3 years.

In general I think we’d notice a steady drop in age-related deaths.

Depending on the mechanism, maybe some biology lab looking at DNA and telomeres over time would notice that they suddenly don’t change anymore.

I see a couple of answers here assume that "maturing" and "degenerating with age" are the same thing, or that both are affected. Biologically, the processes are very different. The biology of aging is still debated, but by at least some theories, "aging" is basically the opposite of "maturing". As a baby grows into an adult cells divide and multiply. When an old person starts falling apart, one theory is that cells are FAILING to divide and multiply to replace dead cells. The body can no longer replenish itself -- exactly why is another subject that I won't get into here, but look up "telomeres" for one theory -- and so dead cells cannot be replaced and the body starts to fail.

If we assume you mean that this phenomenon affects aging but not maturing, I'd say it would take months before anyone would notice, and longer for most people. I'm 62. I can tell that I'm getting little aches and pains and don't have the energy I used to have and so forth. But it's not like this happens on some strict schedule. I mean, it's not like someone could write in a book, "When you reach 60 years, 8 months, and 14 days, you will experience your first sign of arthritis." Some get it sooner and some later. Look at pictures of a bunch of people who are all, say, 60 years old. Some could easily pass for 40. Others you might think are 90.

If I stopped aging tomorrow, how would I know? I might notice that all these little aches and pains aren't getting any worse. But how fast do I expect them to get worse? I don't know. It would be literally years before I was sure that something odd was happening.

My guess is that the first people to notice would not be old people who realize they are not aging any more, but doctors or medical researchers who are studying human or animal patients every day with a microscope, and see that the progressive deterioration has stopped.

If, on the other hand, you are supposing that babies no longer mature, then people would notice very fast. Parents would likely notice within weeks that their child was not maturing properly. Babies in the womb would suddenly stop developing and there would be a massive number of miscarriages. After a couple of months, every baby would be a miscarriage. And doctors would start to notice that there was no longer any sign of new pregnancies.

Why women’s bodies abort males during tough times

In times of trouble, multiple studies have shown, more girls are born than boys. No one knows why, but men need not worry about being overrun by women. An analysis of old church records in Finland has revealed that the boys that are born in stressful times survive better than those born during less challenging periods. The work helps explain why women may have evolved a tendency to abort certain males and could lead to a better understanding of miscarriages.

Males are more likely to die than females while in the womb. Bouts of severely cold weather, earthquakes, natural disasters, even the 9/11 terrorist attack on New York City exacerbate this difference, as months later the ratio of boys to girls born can decline to well below the typical ratio of 105-to-100.

Biologists have long thought that the women spontaneously abort male fetuses that are frail, making room for new pregnancies and, possibly, a healthier baby. (Females are thought to have a better chance of reproducing than males in tough times, so aborting them doesn’t make as much evolutionary sense.) Because of the large investment required to raise children, “there would be a big payoff to being able to select which fetuses to raise and which not,” says Ron Lee, an economic demographer at the University of California (UC), Berkeley.

One outcome of such “culling” should be that healthier sons are born during rough periods. Indeed, in 2006, population health researchers Ralph Catalano and Tim Bruckner of UC Berkeley found this trend in population data from the Human Mortality Database. In those rough years, a greater percentage of boys survived infancy. But Bruckner wanted to get beyond these statistics to see not just if those boys born during stressful times were healthier but also whether they would produce more children than boys born during less stressful times. Such a pattern would provide an evolutionary explanation for such culling. It “might be adaptive,” Lee says.

Bruckner turned to Virpi Lummaa, a biologist at the University of Sheffield in the United Kingdom who had digitized centuries of Finnish church records that documented family histories and recorded other data about every Finn born at those times. The researchers looked at the sex ratios of newborns from 1790 through 1870 and tallied how many males survived infancy, an indication of how healthy the fetus was, and how many children they subsequently had that in turn reached puberty. They found 16 years where the percentage of male infants surviving plunged, with one in the late 18th century dropping to 79 males for every 100 females. Those males did do better than their peers born in normal years, with about 12% more of them surviving past age 1, Bruckner, Lummaa, and their colleagues report online this week in the Proceedings of the Royal Society B. The data also indicated that in the most extreme case, survivors produced 8.7% more offspring than males born in years where the numbers of male and female babies were about equal.

The finding “offers further confirmation of the suspicions that male [fetuses] are more vulnerable to miscarriage than females and that the aborted fetuses are frail,” says psychologist William James, an honorary research associate at University College London who was not involved with the work.

The researchers don’t yet know the stress, such as hunger, that may have been experienced by pregnant women in those unusual years. Still, these data show that “the ambient environment during pregnancy shapes the quality of the males over their lifetime,” Bruckner says. In general men die 5 or 6 years earlier than women. “We’re trying to understand the causes of gender imbalance in life span and what contributes to the variance” in how long individuals live, he adds. Pinpointing what happens to frail males in utero is a first step in that direction.

The study is very intriguing, says Ken Robert Smith, a biodemographer at the University of Utah in Salt Lake City, because “it covers a time when parents had no control over the sex of their children,” and thus “the sex ratio reflects the basic interplay of biology and environment stress.” Comparing the survival of girls during normal and female-dominated sex ratio years would help ensure that males were really more robust and not just benefiting from an environment that was better for all infants, Smith says. Also assessing the survival of siblings would have strengthened the results. And Lee wonders if there’s any way to assess whether the aborted fetus resulted in better care of the siblings or a healthier mother. Regardless, he adds, the work “demonstrates that basic forces that arise early in life have [important] consequences.”

Elizabeth Pennisi

Liz is a senior correspondent covering many aspects of biology for Science.

Watch the video: 13 week baby who died before birth. (January 2022).