A Brush With Extinction

[Kanastrous]

WASHINGTON - Human beings may have had a brush with extinction 70,000 years ago, an extensive genetic study suggests.

The human population at that time was reduced to small isolated groups in Africa, apparently because of drought, according to an analysis released Thursday.

The report notes that a separate study by researchers at Stanford University estimated the number of early humans may have shrunk as low as 2,000 before numbers began to expand again in the early Stone Age.

This study illustrates the extraordinary power of genetics to reveal insights into some of the key events in our species' history," Spencer Wells, National Geographic Society explorer in residence, said in a statement. "Tiny bands of early humans, forced apart by harsh environmental conditions, coming back from the brink to reunite and populate the world. Truly an epic drama, written in our DNA."

Wells is director of the Genographic Project, launched in 2005 to study anthropology using genetics. The report was published in the American Journal of Human Genetics.

Previous studies using mitochondrial DNA — which is passed down through mothers — have traced modern humans to a single "mitochondrial Eve," who lived in Africa about 200,000 years ago.

The migrations of humans out of Africa to populate the rest of the world appear to have begun about 60,000 years ago, but little has been known about humans between Eve and that dispersal.

The new study looks at the mitochondrial DNA of the Khoi and San people in South Africa which appear to have diverged from other people between 90,000 and 150,000 years ago.

The researchers led by Doron Behar of Rambam Medical Center in Haifa, Israel and Saharon Rosset of IBM T.J. Watson Research Center and Tel Aviv University concluded that humans separated into small populations prior to the Stone Age, when they came back together and began to increase in numbers and spread to other areas.

Eastern Africa experienced a series of severe droughts between 135,000 and 90,000 years ago and the researchers said this climatological shift may have contributed to the population changes, dividing into small, isolated groups which developed independently.

Paleontologist Meave Leakey, a Genographic adviser, commented: "Who would have thought that as recently as 70,000 years ago, extremes of climate had reduced our population to such small numbers that we were on the very edge of extinction."

Today more than 6.6 billion people inhabit the globe, according to the U.S. Census Bureau.

The research was funded by the National Geographic Society, IBM, the Waitt Family Foundation, the Seaver Family Foundation, Family Tree DNA and Arizona Research Labs.

http://www.msnbc.msn.com/id/24295165/

[The Vortex Empire]

Isn't that old news?

[Kanastrous]

Possibly.

I hadn't run across it before.

[cosmicalstorm]

I've heard about this a couple of times, usually in connection with the Toba megaeruption-theory, though that might be bunk.

[Tsyroc]

Has anyone else participated in the Genographic Project?

My mom is interested in genealogy and when this came up it also peeked her interest. She asked me if I would do this so I sent in my samples. I was a bit disappointed since part of the reason for me doing it instead of my sister was so the project could trace both my mother's and father's lines with just the one sample. For some reason they only did my Y chromosome.

The report I got is somewhat interesting. It's kind of creepy though how closely related every non-African is.

[The Vortex Empire]

Has anyone else participated in the Genographic Project?

My mom is interested in genealogy and when this came up it also peeked her interest. She asked me if I would do this so I sent in my samples. I was a bit disappointed since part of the reason for me doing it instead of my sister was so the project could trace both my mother's and father's lines with just the one sample. For some reason they only did my Y chromosome.

The report I got is somewhat interesting. It's kind of creepy though how closely related every non-African is.

Well if mitochondrial eve is correct, then we are all descended from one woman.

[GrandMasterTerwynn]

Has anyone else participated in the Genographic Project?

My mom is interested in genealogy and when this came up it also peeked her interest. She asked me if I would do this so I sent in my samples. I was a bit disappointed since part of the reason for me doing it instead of my sister was so the project could trace both my mother's and father's lines with just the one sample. For some reason they only did my Y chromosome.

The report I got is somewhat interesting. It's kind of creepy though how closely related every non-African is.

Well if mitochondrial eve is correct, then we are all descended from one woman.

Umm, this is a gross oversimplification of the theory. It does NOT state that we're all descended from one woman. It states that she is the most recent common ancestor of human beings when you trace our ancestry back through only the maternal lineage, i.e. from mother to daughter. It's not to say we're all descended from her. There were many other women alive at the same time as Mitochondrial Eve. Except some died childless, only had sons, or their daughters failed to produce daughters down to the present day. The most recent common ancestor of presently living human beings probably lived much more recently. No more than a few thousand years ago. In a couple thousand years, the most recent common ancestor for all human beings will either be Temujin, or Charlemagne.

[Kanastrous]

My money's on Temujin.

[Mayabird]

Actually, the most recent common ancestor of every single human on Earth probably lived several tens of thousands of years ago, but the most common ancestor of pretty much but not quite all humans was only a couple thousand years ago. A small number of teeny populations in remote mountainous areas and islands were isolated from contact (and often mostly still are) for millenia, while the rest of the world's population was in constant flux and inter-contact. Also, note that the Khoi and San have been separated genetically from the rest of humanity for 90,000 years or so. It could very well be that 95% of people on Earth can trace ancestry back to one or two people (and Temujin is definitely one of them, especially in Asia), but then there are a scattering of other populations that go much further back.

It's much like how, when looking at the species in the world, a huge chunk will be descended from one or two distant parental species (like all the felines), and then you have a few outliers, like possums.

Also, this IS old news. The genetic bottleneck dating back to about 70,000 years (which is indeed when the Toba supervolcano erupted) has been known for years.

[Kanastrous]

It's a newly-released analysis of the same data, that came out Thursday.

Just confirmation, I think.

[Ariphaos]

Appears to be a confirmation.

Y-adam was dated to originate from around this time as well.

[ray245]

Why is some people so afraid of the idea of a human adam or eve?

I mean, there must be someone who evolved into human beings and populate the world slightly(like when was the first true human born) before other primates evolved into a modern human.

Just because there's a first human around does not mean it is based on the bible...

[Cykeisme]

Would there have been a "first true human"?

I think there would have been a few successive generations within a cluster of humans that would have been "not quite human" at the beginning, and "true human" at the end, but in the middle, they'd still be classified as homo sapiens.

Err, as opposed to there being a particular individual being born who was the first true human, per se.

Or something.

[Kanastrous]

Why is some people so afraid of the idea of a human adam or eve?

I don't know about afraid, buit some people might dislike the idea because it's inaccurate, and misleading.

[ray245]

Would there have been a "first true human"?

I think there would have been a few successive generations within a cluster of humans that would have been "not quite human" at the beginning, and "true human" at the end, but in the middle, they'd still be classified as homo sapiens.

Err, as opposed to there being a particular individual being born who was the first true human, per se.

Or something.

Really? Well, there seems to be so little articles about the transistion stage of evolution around.

But, surely there must be a first true human somewhere down the line, well, the first modern human might be born a few seconds ahead of the next modern human for all we know, before the entire younger generation was filled with modern human.

Applying that concept as the first human seems acceptable to me.

[ArmorPierce]

Since the entire species doesn't transition and evolve in unison, there would have been a first modern human that is what we are today that is slightly different than the others.

[Cykeisme]

Since the entire species doesn't transition and evolve in unison, there would have been a first modern human that is what we are today that is slightly different than the others.

Well, I each mutation would have originally occurred in a single individual, I'm not arguing with that.

What I mean is that the definition of "human" encompasses a particular range of traits; hence, it is unlikely there was a particlar birth that occurred sometime in history, where the parents did not fall under the classification homo sapiens and the offspring did.

[ArmorPierce]

agree it does. Neanderthal were human. There wouldn't be something that just popped out that was half-ape, half-human. Where you draw the line along human evolution of what was and was not human is likely fairly abritary.

[Mayabird]

I dunno if Neandertals could be called "human" or not. They were certainly very closely related and appeared to have human-level intelligence, but it looks less and less likely that they contributed anything to our ancestry.

And yeah, there's no such thing as a transition state. Mutations just occur on a statistical basis and disappear or spread by differential reproduction via selection or luck (like drift).

While I'm here, I would argue that the first true human was the first person who made a breakthrough in using his/her brain (though there might have been a group that all did it together, accidentally - one of them started realizing something about language and as the others caught on it sparked their brains into action and it all just snowballed - I'm speculating, but I'm sure there's a lot of research into how it could have happened). Anatomically modern humans may have been around for almost 200,000 years, but it was only in that last 50-70,000 that humans are seen drastically changing and inventing new tools at a fast pace, leaving jewelry, and other artifacts like that. They had the brain for the first 130,000 years, but they probably didn't know how to use it.

[ArmorPierce]

I dunno if Neandertals could be called "human" or not. They were certainly very closely related and appeared to have human-level intelligence, but it looks less and less likely that they contributed anything to our ancestry.

They are a human species, that does not mean that they were our ancestors. People often think human=homo sapien sapien which is not the case. There were at a time multiple species of humans (a lot of animals have several sub-species) we are merely the last human species left.

[Junghalli]

Would there have been a "first true human"?

I think there would have been a few successive generations within a cluster of humans that would have been "not quite human" at the beginning, and "true human" at the end, but in the middle, they'd still be classified as homo sapiens.

Err, as opposed to there being a particular individual being born who was the first true human, per se.

Or something.

I think you're probably right. New species generally emerge when you have one populations that becomes reproductively isolated from the rest for some reason, and genetic divergences build up to the point where they can't interbreed with the original. So the first Homo Sapiens would probably have been a community of some earlier hominid that evolved divergently. I suppose there could have been a "first true human" in the sense of first person that couldn't reproduce with a member of the old founder species, even that would probably have been pretty nebulous.

The idea of an "Adam" in the true sense of the word is pretty silly. Who'd he have mated with? It'd have to be a member of the original species, and then the offspring would have been 1/2 human, and the grandchildren 1/4 human, etc.

[Mayabird]

I dunno if Neandertals could be called "human" or not. They were certainly very closely related and appeared to have human-level intelligence, but it looks less and less likely that they contributed anything to our ancestry.

They are a human species, that does not mean that they were our ancestors. People often think human=homo sapien sapien which is not the case. There were at a time multiple species of humans (a lot of animals have several sub-species) we are merely the last human species left.

I usually define "human" more narrowly as H. sapiens sapiens but I see what you're getting at. I just think of them as a cousin hominid species to ours. Nothing wrong with that in that my mind. It's probably our ancestors' fault for killing them off anyway.