Humanity's Ancestors Nearly Died Out, Genetic Study Suggests (nytimes.com) 64
Researchers in China have found evidence suggesting that 930,000 years ago, the ancestors of modern humans suffered a massive population crash. They point to a drastic change to the climate that occurred around that time as the cause. The New York Times: Our ancestors remained at low numbers -- fewer than 1,280 breeding individuals -- during a period known as a bottleneck. It lasted for over 100,000 years before the population rebounded. "About 98.7 percent of human ancestors were lost at the beginning of the bottleneck, thus threatening our ancestors with extinction," the scientists wrote. Their study was published on Thursday in the journal Science.
If the research holds up, it will have provocative implications. It raises the possibility that a climate-driven bottleneck helped split early humans into two evolutionary lineages -- one that eventually gave rise to Neanderthals, the other to modern humans. But outside experts said they were skeptical of the novel statistical methods that the researchers used for the study. "It is a bit like inferring the size of a stone that falls into the middle of the large lake from only the ripples that arrive at the shore some minutes later," said Stephan Schiffels, a population geneticist at Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
If the research holds up, it will have provocative implications. It raises the possibility that a climate-driven bottleneck helped split early humans into two evolutionary lineages -- one that eventually gave rise to Neanderthals, the other to modern humans. But outside experts said they were skeptical of the novel statistical methods that the researchers used for the study. "It is a bit like inferring the size of a stone that falls into the middle of the large lake from only the ripples that arrive at the shore some minutes later," said Stephan Schiffels, a population geneticist at Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
Would explain a lot, though. (Score:2)
You need a minimum of around at least 40,000 breeding individuals to prevent harmful mutations such as genetic diseases and severe mental retardation.
Re:Would explain a lot, though. (Score:5, Interesting)
500 is enough for long term viability, but as a species we're not very good at success in small numbers. Supporting our current level of technology takes a LOT more people. Oddly enough, that was not an issue a few hundred thousand years ago.
If your 500 are all gathered in the same geographical area, you're more worried about natural disasters than genetics.
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Anyone know if the "climate change" referred to in the paper was for HOTTER or COLDER climate trends?
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Anyone know if the "climate change" referred to in the paper was for HOTTER or COLDER climate trends?
The climate became colder and Africa became drier. Forest shrank. Savannahs expanded.
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We don't need to support our current level of technology to simply survive.
Food, water, sex is all what you need to keep the human population alive, anything else is a bonus that allows for more humans.
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We don't need to support our current level of technology to simply survive.
You're looking at it wrong. We need a "significant" number of people involved with sustaining the billions of people currently living on the planet. (Its still a tiny fraction of Earth's entire population.)
Food, water, sex is all what you need to keep the human population alive, anything else is a bonus that allows for more humans.
No, that's all that's needed to keep a tiny population of individual humans alive (in a location). The location will then fill up to the maximal capacity of humans the area can support without technology. The human race can probably survive with as few as 500 mating pairs (1K fecund humans). Under th
Re:Would explain a lot, though. (Score:5, Insightful)
500 is enough for long term viability, but as a species we're not very good at success in small numbers. Supporting our current level of technology takes a LOT more people. Oddly enough, that was not an issue a few hundred thousand years ago.
If your 500 are all gathered in the same geographical area, you're more worried about natural disasters than genetics.
Interestingly, if this research holds up it doesn't necessarily mean that we were restricted to 1280 breeding individuals during this period, we were simply restricted to 1280 breeding individuals who were our ancestors.
There could have been multiple pockets of humanity during this period, and many others that did get wiped out.
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>There could have been multiple pockets of humanity during this period, and many others that did get wiped out.
This would be my default expectation. People in early hunter/gatherer groups would cover a fair amount of territory, especially as they were hit with resource shortages and either spread out or died.
It seems unlikely survivors would all find each other and keep clustering into a single group.
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500 is enough for long term viability, but as a species we're not very good at success in small numbers. Supporting our current level of technology takes a LOT more people. Oddly enough, that was not an issue a few hundred thousand years ago.
If your 500 are all gathered in the same geographical area, you're more worried about natural disasters than genetics.
This existential threshold provokes an interesting thought question: Given the complexity and vulnerable viability of humans, how did the first progenitors ever survive? Even 500 individuals takes many decades (centuries?), which means that humans are extremely lucky to still exist. Either mutations and external threats fortuitously didn't exist during that time, or humans happened to amazingly evolve all of a sudden into a state that was able to handle all mutations and threats.
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Given the complexity and vulnerable viability of humans
What does that mean, and where did you get it from?
Average life expectancy, quality of life, and population size will be lower without it, but humans haven't evolved in the past few thousands years to become dependent on modern conveniences or technology. And we've only had nice things in the order of hundreds of years. We're just as capable of surviving they way we did five hundred years ago, or a thousand or several thousand or more.
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If your 500 are all gathered in the same geographical area, you're more worried about natural disasters than genetics.
Mm.... nah, I'm still betting on disease/genetics. We haven't sterilized the rest of the planet in this scenario right?
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Given the current state of affairs, I would argue the opposite: we're not very good in large numbers either. I mean, there's been a couple world wars, countless smaller ones, mass pollution, starvation, etc etc etc despite all kinds of wealth, advanced communications, etc.
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I don't think you can justify that number. It depends on the rate of reproduction and the degree of selection pressure. It sounds, to me, and non-expert, about right. Whether it's the right number for people (low tech, predators not exterminated, etc.) I couldn't guess.
And I don't think there is a large number that eliminates harmful recessive genes. For that you want numbers of isolated populations, that stay isolated until the gene happens to disappear via drift.
Not the only time (Score:5, Interesting)
There was also a genetic bottleneck 70,000 years ago, which geologists have linked to a supervolcano (Toba) in (what is now) Indonesia.
Links to articles: Toba catastrophe theory (Score:5, Informative)
Study Shows How Humanity Survived The Toba Supervolcano Eruption [forbes.com]
"Our work is not only a forensic analysis of Toba's aftermath some 74,000 years ago, but also a means of understanding the unevenness of the effects such very large eruptions may have on today's society,"
survivor bias, or, do ya wanna try for 3? (Score:1)
People of a certain mindset might see that as the Miraculous hand of Providence.
Or plot armor, or something.
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Also every single one of your ancestors going back 200 generations managed to successfully reproduce. Even at high odds of reproducing, the chance that every single one of thousands did, is astronomically low, and yet it happened.
Eg the odds of every one of 10,000 people reproducing, assuming 95% success rate, would be 1 in 10^223, and you have way more than 10,000 ancestors. (1 in 10^223 is roughly the odds of winning the lottery 26 times in a row.)
things will work out, they always do... for me. (Score:2)
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What happened 200 generations ago?
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Small wonder that half of us are retards.
You're really making that claim? I would suggest that there's ample evidence that this is not the case.
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I think it was meant in hyperbole.
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We see in others what we see in ourselves.
Some people see retards wherever they look.
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We see in others what we see in ourselves.
Some people see retards wherever they look.
That's because retards are all over the place. It's difficult not to miss them.
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QED.
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Small wonder that half of us are retards.
You're really making that claim? I would suggest that there's ample evidence that this is not the case.
Maybe not half, but one family in particular [the-sun.com]. And no, they're not from Alabama.
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Look at any bell curve distribution, half of the people are dumber than the other half
Does this confuse you?
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Retarded used to mean below 80, which is two sigmas out.
Back before the offended-by-life people started shrieking about it.
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also you're 6'3" and 215 lb, i assume.
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Small wonder that half of us are retards.
You may belong to that half all right.
extremely not news (Score:3, Informative)
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I checked into it because I thought the same thing - I've heard this story for a very long time. But... this appears to be one of multiple choke points. This one was almost a million years ago - but it also happened 70,000 years ago.
So it probably isn't just a confirmation of prior knowledge - it might, in fact, be net new.
How do they know the number? (Score:3)
The claim is there were around 1,280 breeding individuals left. First, that is an awfully specific number. Second, it's difficult to imagine that across the entire African continent, and possibly lower Europe and into the Balkans, were spread these 1,280 people. Even if they clumped together here and there, that doesn't take into account pair groups or groups less than 10 which wandered about. For 1,280 people to be all that was left at this one point in history seems improbable.
Not saying this couldn't be true, but, extraordinary claims require extraordinary evidence.
Re:How do they know the number? (Score:5, Funny)
Maybe it was the screen resolution they were running Civilization on?
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Possibly, there were many such groups, but all went extinct except for this one.
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Possibly, there were many such groups, but all went extinct except for this one.
Which goes back to my point. How do they know? To say this one group is all that was left seems out there. Across the entire land mass of Africa and, as I mentioned earlier, probably part of lower Europes and the Balkans, they're saying only this group remained? That is a stretch by any imagination. It sounds like something out of a bad science fiction book. "Only 1,280 left to repopulate the world. Where the others went, no one knows. And it's not important."
Even Battlestar Galactica did better. Th
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How do they know the number?
The claim is there were around 1,280 breeding individuals left. First, that is an awfully specific number. Second, it's difficult to imagine that across the entire African continent, and possibly lower Europe and into the Balkans, were spread these 1,280 people. Even if they clumped together here and there, that doesn't take into account pair groups or groups less than 10 which wandered about. For 1,280 people to be all that was left at this one point in history seems improbable.
Not saying this couldn't be true, but, extraordinary claims require extraordinary evidence.
https://www.science.org/doi/10... [science.org]
Hu et al. used a newly developed coalescent model to predict past human population sizes from more than 3000 present-day human genomes (see the Perspective by Ashton and Stringer).
The model detected a reduction in the population size of our ancestors from about 100,000 to about 1000 individuals, which persisted for about 100,000 years.
The decline appears to have coincided with both major climate change and subsequent speciation events.
https://en.wikipedia.org/wiki/... [wikipedia.org]
They don't really know the number, they just have a new version of an already shakey mathematical model to derive the number.
The details of their changes to the model are behind a paywall but the wikipedia link describes the general idea they are using.
I have to agree with you, with no evidence the model has ever correctly predicted any verifiable outcomes, this might be more of "statistician running amok" again.
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I agree that's too specific a number. But if it was a million years ago, it's quite possible that all the folks who survived lived in a rather restricted area. I think that's about the time the put a hominid extinction in Europe, but perhaps it wasn't only Europe. Maybe the only folks who survived lived around Turkey and Greece. (It's hard to see how southern Italy would have been hit, but perhaps they became the "traditional enemies" and were wiped out. Or maybe Italy was lacking in safe water.)
But I
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First, that is an awfully specific number.
Not surprising. They take a sample of the genetic variations, and then calculate the permutations that could result in that number of genetic variations. And it doesn't mean there had to be exactly 1280 breeding individuals. It just means that breeding population X needed that many successful breeding individuals to account for the genetic population traits. The population could have been higher, and those people bred extra decendents, but their decendents didn't survive to successfully produce offsprin
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Meanwhile Extinction Rebellion (Score:1)
Wants to recreate that. If they're serious about their belief, they really should invite everyone they know to a nice Kool-Aid party and appease Gaia.
Studies (Score:2)
Studies in the morning,
Studies in the evening,
Studies at supper time.
Be my little study,
And love me all the time.
Always a problem... (Score:2, Insightful)
They point to a drastic change to the climate that occurred around that time as the cause.
Cavemen and their need to drive their stupid SUVs for dinosaur hunting causing trouble even a million years ago.
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Tautology (Score:2)
All of humanities ancestors actually did die out. That's why they're humanity's ancestors, and not humans. There's no way to know the number of species between single cell and human. There really isn't a definitive answer to how many varieties of primates are in the direct lineage of humans, or even the number of species categorized as human. We find out about human species when one happens to be fossilized where we decide to dig. We may have found evidence of 90% of all human species, or less than 1%. It
So....what you are saying (Score:2, Insightful)
Re: (Score:2)
Wait 'till they hear about pole shifts!
Oy, vey.
Model Confidence? (Score:4, Informative)
Looking backward in time: Because DNA is not infinitely divisible, a person can have a genetic 9th Great Grand that contributed zero DNA to their DNA -- It takes just 200 years to lose the thread of DNA for non-Y/non-MT DNA for some ancestors.
Looking forward in time: even with modern medicine, etc, most lineages die out within a dozen or so generations -- most people living today will have no descendants in 12 generations. And as noted above, at 12 generations even if you have direct descendants there is only a 1:7 chance that they have any of your DNA except for the cases of direct male/female lines which comprise just 1/4096th of possible descendant bloodlines at 12 generations.
These limits on information propagation put some big limits on what we can reasonably assert over very long time spans like 100,000 years. Saying there was a likely bottleneck is one thing, saying it spanned 100,000 years is an entirely different matter.
Another way to look at it:
World Pop year 1000: 275,000,000
World Pop today if all lineages since year 1000 survived: 7x10^38
World Pop today: 8x10^9
Odds you would be here starting with ancestors circa 1000: 10^-29
This is just for a little over 1000 years, not 100,000 years. When creating models when the propagation likelihoods are so infinitesimal you are necessarily toying with the limits of information propagation and therefore confidence.
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Looking backward in time: Because DNA is not infinitely divisible, a person can have a genetic 9th Great Grand that contributed zero DNA to their DNA -- It takes just 200 years to lose the thread of DNA for non-Y/non-MT DNA for some ancestors.
Looking forward in time: even with modern medicine, etc, most lineages die out within a dozen or so generations -- most people living today will have no descendants in 12 generations. And as noted above, at 12 generations even if you have direct descendants there is only a 1:7 chance that they have any of your DNA except for the cases of direct male/female lines which comprise just 1/4096th of possible descendant bloodlines at 12 generations.
That's all well and good but we're not talking about individuals here. We're talking about the entirety of the human genome. The likely coefficient of relationship between you and me is somewhere between 13th and 15th cousin, and yet on average, you and I share 99.4% of our genes. DNA is not infinitely divisible and it is also not infinitely variable. Human DNA in particular is unusually homogeneous compared to other species on Earth. And yet, because there's so very much of it in our chromosomes, that
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World Pop year 1000: 275,000,000
World Pop today if all lineages since year 1000 survived: 7x10^38
Why is population growth required for all those peoples lineages to be here today?
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Looking backward in time: Because DNA is not infinitely divisible, a person can have a genetic 9th Great Grand that contributed zero DNA to their DNA -- It takes just 200 years to lose the thread of DNA for non-Y/non-MT DNA for some ancestors.
All the DNA needs to come from the ancestors.
On average, if generation A has a total population of X and generation B a total population of Y then the average amount of your DNA persisting for a person from generation A is X/Y.
In other words, if population doubles the
More such incidents than Toba at 75k years ago? (Score:2)
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More such incidents than Toba at 75k years ago?
Quite a few more. We've been repeatedly genetically bottle-necked. It's one likely explanation for why there are such distinct human phenotypes. Isolated groups of humans who suffered severe reductions in genetic diversity would rebound looking very similar to each other and much less similar to everyone else.
Basically the human "races" are just like dog breeds, with distinct phenotypes induced by external forces, yet we're all still the same species.
Never trust an anthropologist (Score:2)
"It is a bit like inferring the size of a stone that falls into the middle of the large lake from only the ripples that arrive at the shore some minutes later," said Stephan Schiffels, a population geneticist at Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
So.... really accurate? Characteristics of a Linear Plane Progressive Wave. [mit.edu] The velocity field equations are on page 8. (I'm not quoting all the Greek letters in the formulas because Slashdot.) This is coursework for college kids. It's called Marine Hydrodynamics and it's an incredibly well-studied field. And of course if you have stupid amounts of processing power you can always run a Navier-Stokes equation simulation in reverse. That's a fairly good analogy for the statistical analysis of the whole
Bias? (Score:2)
I'm pretty skeptical of anything Chinese scientists say about the origins of modern humans, given that the Chinese Communist Party still promotes the (largely discredited) idea that human origins come from Peking Man (because of course they do).