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)
Interesting. But would the ice age also affect African populations? And if so, as much as in Europe?
This is not new. The skin pigmentation changes during the European ice age has been well known since the 1960s.
They must have been burning fossil fuels back then. And just think, the population must have been at least twice as many as there are now since they had a severe case of global warming then.
The real question - "Where are the fossilized SUV's?"
I'm not buying it.
Since there is no such thing as concurrent "group" evolution, the necessary predicate for this theory is that all human life descended from a common ancestor 15,000 years ago. Everyone else had to have lost the evolutionary race and died out. With humans allegedly scattered widely over the face of the earth long before that, this theory is specious.
Ice ages don't just impact the areas under or near the ice sheets. Major climate pattern changes happen everywhere. For instance the Sahara region and the Levant were relatively lush well watered areas. Change from a wet to a dry climate and you change the food sources. That change can lead to various selections.
Interestingly, while the Scandinavians are fair complexioned, the Eskimos are dark skinned.
And are relatively recent arrivals to the Arctic (probably about 6,000 years ago, I believe).
Thanks...makes sense. And, I guess, it's a question of degree of change.
Probably because the Eskimos arrived from Asia fairly recently.
What? ToE shows how natural selection acts on individuals, but its evolutionary effect is on the population's gene pool, not the individual.
But, consider, 6,000 years and no evolutionary change toward fair complexion? THeir complexion is as dark as residents of South China.
How, then, can we confidently deduce that light-complexioned scandinavians "evolved" in 10,000 or 15,000 years? Where's the evolutionary advantage in that if Eskimos aren't visibly evolving in the same basic climate?
This is quite interesting and parallels some ideas I have had for awhile, which have only recently been confirmed.
I have always shied away from margarine and all the pseudo good for ya crap that goes on, and I appreciate and use moderate amounts of butter and animal fats, even though they are the saturated kind.
My belief always was that hey, we've been eating this stuff for the last hundred thousand years or so, etc.
Turns out your body DOES know how to digest stuff like that. But trans fats, and hydrogenated vegetable oils, that they've been telling us for years and years and years is "Good for ya" are only about four hydrogen atoms away from being legally and chemically classified as PLASTICS.
We are making great strides in genetics and molecular biology. Within 15 years we WILL KNOW HOW TO HELP A PERSON LIVE TO 200 YEARS OLD.
But geezer that I am, I probably won't make it myself!
But evolution MUST start with a random, non-directed mutation in an individual, won't you agree? And then that individual's progeny must out-compete the other individuals, right?
Don't run away from the "ToE" as you call it.
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Huh? Of course there is. It's called gene flow and it's one of the four basic evolutionary mechanisms.
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