When Humans Faced Extinction

BBC ^ | 6-10-2003 | Dr David Whitehouse

[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.

[CobaltBlue]

>>we are speaking about time periods that are virtually incomprehensible to humans<<

Yes, just thinking about it gives me a headache, and makes me feel very small. Same thing for John McPhee's books about geology, which really give a sense of the immensity of geological time.

But when I look at the pictures on Astronomy Picture of the Day, I don't feel small at all, just a childlike sense of wonder.

[Mamzelle]

re: Real scientific research doesn't rest on hands waving. ))

Of course it does not, which is exactly my point. When researchers of the origins of matter and life come to the public, it would do well to dispense with condescension and the "I'm afraid this is all beyond you, dear, leave it to the researchers and drop the grant money at the door" attitude.

Such statements of the writer, "It is thought that we split off from chimps 5-6 million years ago"--takes no rocket scientist (or paleantologist) to penetrate-- this makes an assumption so vast, so presumptuous, that some technique must be employed to patch over it quickly. A miracle needs to happen. So, slip into the passive voice, and insinuate that anyone demanding common sense is simply beyond the Pale.

Yet, see how effective such a sentence is. To take issue with the entire foundation is to put one's self open to accusations of superstition and insinuations of ignorance. No wonder people like me would like to see the grant money dry up.

Scientists are numerous now, and compete heartily for attention and resources. They deserve every bit of skepticism they receive, and they don't receive nearly enough.

Peer review? Huh. How about "this is my sandbox, and you can't have it." Take a little more jaded look.

[blam]

"On second thought, if your mama saved her seeds every year, no telling what she grew, it could have been something she developed all on her own. If you grow the old style tomato, not the hybrid kind, but the kind they call heirloom now, they are open pollinated and so you can get new varieties due to pollination, especially if you grow different varieties."

Yup. She had her own seeds...very protective of them too.

[CobaltBlue]

>>She had her own seeds<<

Maybe she shared them with a relative, friend, or neighbor? Sort of like sharing a favorite recipe.

Doubtful but you never know unless you ask.

[stuartcr]

Absolutely....it does make one wonder how it could all have come about.

[SunkenCiv]

Not a ping, just a GGG update.

Please FREEPMAIL me if you want on, off, or alter the "Gods, Graves, Glyphs" PING list --
Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
The GGG Digest -- Gods, Graves, Glyphs (alpha order)

[Ciexyz]

I've always wondered "Who did Cain marry" and "who went to live in the city that he built."

Reminds me of the email going around titled "God's Answering Machine", where, among other items of info (Press "1" for English, "2" for Hebrew, "3" for Aramaic, "4" for other), the instructions are: "For information concerning questions like "How did Noah's Ark float", just wait till you get here.

[Phsstpok]

I wonder what happened to these people?

Ummmmmm..... they died?

Sorry. Slinking away into the muck and mire for having stated the obvious.....

[SunkenCiv]

Just updating the GGG information, not sending a general distribution.

To all -- please ping me to other topics which are appropriate for the GGG list. Thanks.

Please FREEPMAIL me if you want on or off the
"Gods, Graves, Glyphs" PING list or GGG weekly digest
-- Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
Gods, Graves, Glyphs (alpha order)

[SunkenCiv]

from four years ago (so the event described happened 70,004 years ago):

· join · view topics · view or post blog · bookmark · post new topic ·

[Larry Lucido]

Ditto. And He tweaked the process as He saw fit.

And took his time with it, the allegorical account of creation notwithstanding.

[Zon]

Nobody really knows the First Cause.

Existence is axiomatic. Existence exists. What's the alternative? ...The complete contradiction that existence doesn't exist.

[SunkenCiv]

· join list or digest · view topics · view or post blog · bookmark · post a topic · subscribe ·
	Gods Graves Glyphs	Just updating the GGG info, not sending a general distribution. To all -- please ping me to other topics which are appropriate for the GGG list. GGG managers are SunkenCiv, StayAt HomeMother, and Ernest_at_the_Beach
·Dogpile · Archaeologica · LiveScience · Archaeology · Biblical Archaeology Society · · Discover · Nat Geographic · Texas AM Anthro News · Yahoo Anthro & Archaeo · Google · · The Archaeology Channel · Excerpt, or Link only? · cgk's list of ping lists ·