Posted on 06/10/2003 8:05:32 AM PDT by blam
When humans faced extinction
By Dr David Whitehouse
BBC News Online science editor
Humans may have come close to extinction about 70,000 years ago, according to the latest genetic research.
From just a few, six billion sprang
The study suggests that at one point there may have been only 2,000 individuals alive as our species teetered on the brink.
This means that, for a while, humanity was in a perilous state, vulnerable to disease, environmental disasters and conflict. If any of these factors had turned against us, we would not be here.
The research also suggests that humans (Homo sapiens sapiens) made their first journey out of Africa as recently as 70,000 years ago.
Little diversity
Unlike our close genetic relatives - chimps - all humans have virtually identical DNA. In fact, one group of chimps can have more genetic diversity than all of the six billion humans alive today.
It is thought we spilt from a common ancestor with chimps 5-6 million years ago, more than enough time for substantial genetic differences to develop.
The absence of those differences suggests to some researchers that the human gene pool was reduced to a small size in the recent past, thereby wiping out genetic variation between current populations.
Evidence for that view is published in the American Journal of Human Genetics.
Oldest members
Because all humans have virtually identical DNA, geneticists look for subtle differences between populations.
One method involves looking at so-called microsatellites - short, repetitive segments of DNA that differ between populations.
These microsatellites have a high mutation, or error, rate as they are passed from generation to generation, making them a useful tool to study when two populations diverged.
Researchers from Stanford University, US, and the Russian Academy of Sciences compared 377 microsatellite markers in DNA collected from 52 regions around the world.
Analysis revealed a close genetic kinship between two hunter-gatherer populations in sub-Saharan Africa - the Mbuti pygmies of the Congo Basin and the Khosian bushmen of Botswana.
First migration
The researchers believe that they are "the oldest branch of modern humans studied here".
The data also reveals that the separation between the hunter-gatherer populations and farmers in Africa occurred between 70,000 and 140,000 years ago. Modern man's migration out of Africa would have occurred after this.
An earlier genetic study - involving the Y chromosomes of more than 1,000 men from 21 populations - concluded that the first human migration from Africa may have occurred about 66,000 years ago.
The small genetic diversity of modern humans indicates that at some stage during the last 100,000 years, the human population dwindled to a very low level.
It was out of this small population, with its consequent limited genetic diversity, that today's humans descended.
Small pool
Estimates of how small the human population became vary but 2,000 is the figure suggested in the latest research.
"This estimate does not preclude the presence of other populations of Homo sapiens sapiens (modern man) in Africa, although it suggests that they were probably isolated from each other genetically," they say.
The authors of the study believe that contemporary worldwide populations descended from one or very few of these populations.
If this is the case, humanity came very close to extinction.
Somewhere in Indonesia I read that human activity had been discovered just above the Toba ash level, I wonder what happened to these people?
The Khosian Bushmen are physically unique among humans alive today. The females have a skin 'apron' over their genetial area and the men have a perpetual semi-erect penis. Their children are also born with Mongoloid spots.
The actual number was 8 and it happened a lot more recently than that.
There goes the "I just came out of the water" excuse...sucks to be them...hehe
I don't think it's impossible that this marked such a fundamental change that all who didn't have it couldn't compete.
Remember, when you're reading these reports, what they don't say. They don't say (or shouldn't) that this group of 2000 were the only humans alive. Just that all humans alive are descendents of those 2000, and not of any others.
I don't find it impossible to believe that those groups who had developed language simply stopped breeding with those that had not, and over the 30,000 years between the genetic choke-point and the archeological record of ubiquitous culture, simply supplanted those proto-humans who did not have the genetic capability for language.
Mungo Man may represent the dead-end line of humans that survived the Toba super-volcano explosion 75,000 years ago.
There is an on-going argument to reduce the age of Mungo Man so that he fits into the 'Out-Of-Africa' theory. His DNA is unlike any human alive today, yet he has the body of 'modern humans.' (They're pulling their hair out over this one)
Yeah, it's hard to get anywhere with somebody who doesn't understand "If I said you have a beautiful body would you hold it against me?"
Not me. I don't believe the 'Out-Of-Africa' BS. I'm a 'multi-regionalist.'
I agree. See my post #10. I expect there are other Mungo Man types out the yet to be discovered. I also believe we are Neanderthals but the DNA does not support that view. (Neanderthals may be the most recent dead-end at 27,500 years ago.)
I second the earlier poster who said the size of the human population after the cataclysm was only 8 and the date of the cataclysm was not long ago at all.
"Researchers at the John Radcliffe Institute of Molecular Medicine in Oxford say that the so-called “ginger gene” which gives people red hair, fair skin and freckles could be up to 100,000 years old."
Aside from having a headache from the noise they may have died out from the environmental degradation the followed the eruption.
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