Posted on 05/08/2006 2:59:09 PM PDT by SirLinksalot
Many human genes evolved recently
01:00 07 March 2006
NewScientist.com news service
Melissa Lee Phillips
Human genes involved in metabolism, skin pigmentation, brain function and reproduction have evolved in response to recent environmental changes, according to a new study of natural selection in the human genome.
Researchers at the University of Chicago, US, developed a statistical test to find genomic regions that evolution has favoured over the last 15,000 years or so – when modern humans dealt with the end of the last ice age, the beginning of agriculture, and increased population densities.
Many of the 700 genes the researchers identified – especially those involved in smelling, fertility, and reproduction – are also suspected of having undergone natural selection during the divergence of humans and chimpanzees millions of years ago.
But some of the newly identified genes fall into categories not previously known to be targets of selection in the human lineage, such as those involved in metabolism of carbohydrates and fatty acids.
Milk lovers “It’s reasonable to suspect that a lot of these are adaptations in response to new diets and agriculture,” says team member Jonathan Pritchard.
For example, gene variants that improve the digestion of lactose have become more common, presumably since the domestication of cattle provided a ready source of milk. And in some Europeans, genes giving a lighter skin have increased in frequency, as populations have moved north to regions where there is less sunlight to generate vitamin D.
The researchers analysed the genomes of 209 people from Nigeria, East Asia, and Europe. They found widespread signals of recent selection in all three populations.
Only one-fifth of the 700 genetic regions identified were shared between at least two of the groups – the rest were unique to single populations. That supports the idea that the adaptations are recent, Pritchard explains.
Huge list The statistical test is a “powerful way of looking for selection in the genome”, says Michael Hammer of the University of Arizona in Tuscon, US. It looks for certain patterns of DNA – called linkage disequilibrium – that show a gene variant is young. It then identifies those that appear at high frequencies, which suggest they have been selected for.
Definitive proof that the gene variants are being favoured in the human genome will require detailed analysis of the changes they cause in proteins and how this affects fitness. But Hammer says “they’ve given us a huge list of candidates".
Nonetheless, there are likely to be many more, says Peter Andolfatto of the University of California, San Diego, US: “The genes being mapped here at best probably account for only a small fraction of the targets of recent selection in the human genome.”
Identifying the gene variants that are under selection may one day help medicine, Pritchard adds. That is because individuals with a newly evolved gene variant may be better adapted for modern human conditions and less susceptible to certain diseases. Understanding the differences could help guide future therapies.
Journal reference: Public Library of Science Biology (vol 4, p e72)
Also, Oppenheimer says that about 50% of Europeans can trace their lineage to one guy from the Indus Valley who made their way to Europe through the Middle East. The other (about) 50% can trace their lineage to a son of the same guy who made their way to Europe a thousand years later through Russia.
Lack of exercise. Noboby in the western world does physical labor anymore.
Saw a show on PBS where they were doing studies of the markers on the Y chromosome and proved pretty conclusively that the origins of man were distant anscestors of African bushmen.
The mtDNA side tells us about the origins of women.
Who knows? Maybe the space aliens really did manufacture us, and modern tech can prove it!
Thanks.
You know I love this stuff. If I had to do it all again, I think I would have gone into anthropology instead of chip-making. (Of course, I probably wouldn't be retired now though, lol.)
"Interestingly, while the Scandinavians are fair complexioned, the Eskimos are dark skinned."
Study the Lapps of Scandinavia and Russia. Also called Sami. They are not asian in appearance; more like other Europeans.
I'll GGG this one after midnight.
Presently, I worry that we don't completely understand DNA well enough to make all the declarations about human origins that some are making.
Up until the last century, humans were much more physically-active than Americans are today. Eating well will not keep you in good shape without exercise
Older Dryas (very cold glacial period) was about 15K years ago, Younger Dryas about 12-13K.
End of Younger Dryas is associated with the beginning of agriculture.
People are clustered into tiny groups during maximum glaciation, all kinds of interbreeding, then they spread out.
It's called founder effect.
Individuals don't have to "out compete" in order to pass on genes.
If everybody else is killed by, say, a volcano, or a comet, the survivor isn't necessarily fitter, just lucky.
Genes don't compete, they're free riders.
Everybody is so hot on competition. You guys!
If all the tall, smart, strong guys march over a cliff, and all the weak, sniveling, spineless ones stay home, guess who reproduces?
I blame Bush! (And global warming).
I immediately thought of Aurel Stein. He is the original discoverer of the Mummies Of Urumchi in the Tarim Basin back in the very early 1900's. He thought they were Silk Road travellers that had died.
They aren't?
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