Tuesday, 11 December 2007

Old Blue Eyes

Except there aren't any. Old Blue Eyes. Not older than 10,000 years, at any rate.

Let me explain... as I blogged earlier, the human species is mutating rapidly. Now comes an article in Scientific American on the subject which explains a bit of the detail, and contained at least one thing I found surprising.
Homo sapiens sapiens has spread across the globe and increased vastly in numbers over the past 50,000 years or so—from an estimated five million in 9000 B.C. to roughly 6.5 billion today. More people means more opportunity for mutations to creep into the basic human genome and new research confirms that in the past 10,000 years a host of changes to everything from digestion to bones has been taking place.

"We found very many human genes undergoing selection," says anthropologist Gregory Cochran of the University of Utah, a member of the team that analyzed the 3.9 million genes showing the most variation. "Most are very recent, so much so that the rate of human evolution over the past few thousand years is far greater than it has been over the past few million years."
Some things that used to be fatal are now mere disadvantages. Other things which were merely "nice to have" are now all but essential. A case in point: in Northern Europe and Africa, most adults can digest milk. That's not necessarily true in North-East Asia, where many are lactose intolerant. But they worked around that by inventing yoghurt, which can be digested after fermentation, even by people to whom milk is an effective laxative.
Roughly 10,000 years ago, humanity made the transition from living off the land to actively raising crops and domesticated animals. Because this concentrated populations, diseases such as malaria, smallpox and tuberculosis, among others, became more virulent. At the same time, the new agriculturally based diet offered its own challenges—including iron deficiency from lack of meat, cavities and, ultimately, shorter stature due to poor nutrition, says anthropologist John Hawks of the University of Wisconsin–Madison, another team member.

"Their bodies and teeth shrank. Their brains shrank, too," he adds. "But they started to get new alleles [alternative gene forms] that helped them digest the food more efficiently. New protective alleles allowed a fraction of people to survive the dread illnesses better."
...
"Ten thousand years ago, no one on planet Earth had blue eyes," Hawks notes, because that gene—OCA2—had not yet developed. "We are different from people who lived only 400 generations ago in ways that are very obvious; that you can see with your eyes."

I'm interested in this kind of thing for reasons that should be obvious.


Evolution of the Female Brain
(Click to enlarge)

4 comments:

Asher Abrams said...

Fascinating. Thanks for sharing this.

Jordan said...

Zoe,

John's got a interesting new post dealing with some rare questions on acceleration over at his blog.

Also, if you're interested in more detailed discussion on OCA2, etc., I'd suggest checking out Razib and p-ter's posts either at Gene Expression or the Seed version of gnxp.

mythusmage said...

Let me second Jordan's recommendation of Gene Expression. There's also a link to the Seed version there. Razib has been covering the subject in some detail at both places.

Zoe Brain said...

Great links! Must add GE to the blogroll, I keep on losing its URL.

My articles tend towards simplified PopSci, but I like a bit more meat when I'm not tied to communicating with a non-specialist but scientifically literate audience. GE is just right there.