Thursday, April 13, 2006

Still Evolving, Human Genes Tell New Story

Interesting new research on evolution and genes. From The New York Times:

Providing the strongest evidence yet that humans are still evolving, researchers have detected some 700 regions of the human genome where genes appear to have been reshaped by natural selection, a principal force of evolution, within the last 5,000 to 15,000 years.

The genes that show this evolutionary change include some responsible for the senses of taste and smell, digestion, bone structure, skin color and brain function.
From The Economist:
Perhaps the most intriguing results were those connected with food metabolism. The gene for alcohol dehydrogenase is undergoing selection in Asia, as is that for processing sucrose (table sugar). Meanwhile, the genes for processing two other sorts of sugar, lactose (found in milk) and mannose (found in some fruit) are changing in Europeans and Yoruba respectively. Fatty-acid metabolism, too, is changing in all three populations. And Europeans are having the toxin-disposal systems in their livers modified.
You can read the actual report here which also mentions differences in brain genes:
Though there is not an overall enrichment for neurological genes in our gene ontology analysis, several other important brain genes also have signals of selection, including the primary inhibitory neurotransmitter GABRA4, an Alzheimer's susceptibility gene PSEN1, and SYT1 in Yoruba; the serotonin transporter SLC6A4 in Europeans and East Asians; and the dystrophin binding gene SNTG1 in all populations.
It is amazing to me that this research was all done via computer with mathematical models. Biological research is moving from in vitro to in silico. Now that DNA from many people and even our distant human ancestors are all online, doing a "lab experiment" now becomes writing some code to apply a mathematical model or algorithm to the data.

The fact that genes for skin color and metabolism have changed is not very surprising. The ones on brain size and function are going to be very interesting as they find out more about what those genes actually do. It seems plausible that genes affect intelligence, aptitude, disposition and the way brains work. But, man I wouldn't want to be the scientist that had to report those results.

Another impact on this study, is all of the diets and psychology out there based on "how humans have been for tens of thousands of years". Diets like the PaleoDiet or Caveman diet assume that humans are biologically the same as we were when we were hunter gatherers 10,000 years ago. This research shows that there have in fact been noticeable changes to the genes and biology of humans in the last 10,000 years. So the enzymes in our stomachs have been altered by the many generations that lived on an agricultural based diet. There are those that believe that raw food is healthier for humans, as cooking food is not "natural". But, once again it looks like there has been more than enough time for the genes of humans to have evolved to expecting cooked food.

The research wasn't very precise about when these genes first evolved and how many generations it took for them to become common. I think that would make for a good follow up study. I would also be interested in which genes have become much more common in the last say 200 years. Where is evolution pushing us today?

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