When humans faced extinction

[Ayinde]

By Dr David Whitehouse
BBC News Online science editor
Monday, 9 June, 2003

Humans may have come close to extinction about 70,000 years ago, according to the latest genetic research.

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.

http://news.bbc.co.uk/1/hi/sci/tech/2975862.stm

Also Visit ...

The Hominid Species Timeline

Institute of Human Origins

Human evolution chart

The Biological Anthropology Web

A Multimedia Guide to the Fossil Record

The Leakey Foundation

Human Evolution: A Look at Our Ancestors

Anthropology in the News

The Cradle of Humankind

[Ayinde]

Neanderthals Out, Cro-Magnons In As Human Ancestors

By rickyjames

New mitochondrial DNA studies on Cro-Magnon and Neanderthal bone samples show no apparent genetic matches between the latter and modern humans. The results indicate that Neanderthals seem to have made little or no contribution to the genes of modern humans. This conclusion is at odds with a harmony-among-different-species statement made in a museum scene early in the current film X2: X-Men United, but squares with earlier scientific work. "This discontinuity is difficult to reconcile with the hypothesis that both Neanderthals and early anatomically modern humans contributed to the current European gene pool," said study leader Giorgio Bertorelle of the University of Ferrara in Italy.  

His research compared samples of two Cro-Magnons from around 25,000 years ago found in Italy with four Neanderthals who lived from 29,000 to 42,000 years ago. Although no matches were found, the Cro-Magnon samples matched 14% of modern humans found in the Near and Middle East. The report lends further evidence to the theory that anatomically modern humans emerged from Africa some 150 000 years ago and eventually displaced earlier humans, such as Neanderthals, in Europe, but without mixing. Bertorelle's research is published in the current issue of Proceedings of the National Academy of Science (PNAS).  

###

by Bob

An article published in the American Journal of Human Genetics proposes that the human species dwindled to as few as 2,000 individuals, or about the size of Acton, Maine, around 70,000 years ago and could have easily been wiped out by a single disease or environmental catastrophy.

Researchers from Stanford University and the Russian Academy of Sciences compared DNA markers from more than fifty regions around the world, and used computer models to arrive at this conclusion. This explains the relatively minor variations in human genes between individuals, as compared to other species such as chimpanzees.

For the full story, see the articles from the BBC News and the Australian Broadcasting Corporation.


http://www.sciscoop.com/?op=search&topic=Anthropology

[djonmaila]

I read about the near-extinction issue a few years ago. The researchers then were saying that the bottle neck was caused by some catastrophe like a meteor shower or something, or a series of events that between them left most of our species dead. They said it took out as much as 95% of our genetic diversity somewhere around 50 thousand years ago. It's incredible.

[nomo8]

The displacement/extinction theory rests somewhat on social darwinist assumptions common to mainstream science in anthropology.  These statements of "fact" are not resolved among scientific community.  Historically, scientists rarely can agree on anything, such is its nature of critical inquiry.  DNA analysis : does anyone understand it except for "experts"? You are demanded of to believe it.  Can the entire history of human evolution/transformation truly be mapped with certaintly based on a few skull fragments and claims of cellular biologists who are given large research grants to prop up certain views held by establishment?  Much like cosmology and Newtonian physics,  we are looking at 18 and 19 century belief systems. 

Cataclysmic volcanic eruptions are no doubt a part of the various transformations of human society, along with a host of other environmental factors.  However, is it not a stretch to beleive that the scientific priesthood which has been such a failure of late (gravity based vs electric based foundation of the cosmos...eugenics as well) can "tell" us that the human race of "modern" homo sapiens is derived from the scant remnants of survivors from ONE cataclysmic volcanic eruption.  Also, how much of this is based on computer modelling?

Wheras at one time, much physical evidence existed suggesting the interbreeding of various human lines in Europe and Asia with AFrican homo erectus or sapiens, coalescing into what is percieved as modern humans (this itself may be dubious), the cellular biologists came along with smoke, mirrors and blinking lights to interpret for us that one "race" wiped out all the others and never interbred with, say neanderthal (just look at some northern europeans ).  Now, DNA is used to create "evidence" proving identity, beyond doubt supposedly, in legal proceedings.  I hope you can see where this is heading - infallaible "evidence" that only a priest (scientist) can interpret, and worse, that can be planted anywhere at anytime (cellular material).  The scandal at the FBI crime lab regarding DNA may seem far afield from this discussion....But it is not. The O.J. jury properly nullified the prosecution's case and based on that trial, the criminal negligence of the FBI was proven beyond doubt in later investigations having to do with creating guilt by scientific fraud !  Barry Scheck was dead on, though ridiculed at the time by overwhelming majority of white americans as an outrageous lying  lawyer who would say anything for what he was paid during the OJ trial.

People in science are often paid to make predictions or to back up with certaintly long held views, prejudices and much of the reasoning behind it is money based. Many of the greatest scientists who changed views based on honest research and ethical training have been mavericks discredited in their own time, amost always having to do with the money game and certain propaganda streams that are served by what has been already "established" through rigid conformity (which is anti science, pro priesthood). .

The writer has had experience professionally with paid "whores" in the legal area (scientists who testify as experts) and if the public knew just how much this carries over into academia as well, they would be fairly shocked.

 These theories seem to suggest armeggedon doomsday scenarios with a survivalist bent blanketed with racial overtones.  The "science" of physical anthropology is laden with overly-broad speculation based on scant evidence.  Anthropology and archeology are tainted by fraud and blatant criminality. AFricans should know this well based on experience.   Here, a certain group could be patronized while hiding in the background is justification for social darwinism and race/extinction theory of evolution based on competetion between groups.   N*