A morphing demonstration of human evolution shows the transformation from a small lemur, up the evolutionary ladder into a human: seen here as legendary evolutionary biologist Stephen Jay Gould.
Up. The evolutionary. Ladder.This bit of absurd teleology, which is I’m sure causing Gould to spin at high revolutions in his grave (or urn or whatever), accompanies a press release about an article on Natural Selection.The press release starts out with: “Stephen Jay Gould would have been pleased…”Well, maybe about the article, but not about the ladder of evolution bit.The press release itself starts out with a straw man, claiming that between 1970 and 2000 most people believed that while natural selection was important, most evolutionary change did not involve it. But, the press release goes on it turns out it is.Of course, it was Stephen Gould himself who did the most to undo slectionist thinking of the mid 20th century. And no, Natural Selection has NEVER gone out of favor by evolutionary biologists. Geneticists of various stripes have felt that Natural Selection is not too important, but that has not been the only voice regarding this particular issue.
“From 1970 to 2000, there was a widespread view that although natural selection is very important, it is relatively rare,” said Jonathan Pritchard, a geneticist at the University of Chicago. “That view was driven largely because we did not have data to identify the signals of natural selection. . . . In the last five years or so, there has been a tremendous growth in our understanding of how much selection there is.”That insight has only deepened as scientists have gained the ability to read the entire human genome, the chain of “letters” that spell out humanity’s genetic identity.”Signals of natural selection are incredibly widespread across the human genome,” Pritchard said. “Everywhere we look, there appears to be very widespread signals of natural selection in many genes and many processes.”Pritchard helped write a recent paper that identified some of those changes. The paper was published in the public access journal PLoS Biology.The research offers a fascinating snapshot into how the human genome has continued to change as humans adapted to new circumstances over the past 10,000 years. As people went from hunter-gatherers to agricultural societies, for instance, there is evidence of genetic adaptations to new diseases and diets.
Here is the abstract from the actual paper in PLoS Biology:
The identification of signals of very recent positive selection provides information about the adaptation of modern humans to local conditions. We report here on a genome-wide scan for signals of very recent positive selection in favor of variants that have not yet reached fixation. We describe a new analytical method for scanning single nucleotide polymorphism (SNP) data for signals of recent selection, and apply this to data from the International HapMap Project. In all three continental groups we find widespread signals of recent positive selection. Most signals are region-specific, though a significant excess are shared across groups. Contrary to some earlier low resolution studies that suggested a paucity of recent selection in sub-Saharan Africans, we find that by some measures our strongest signals of selection are from the Yoruba population. Finally, since these signals indicate the existence of genetic variants that have substantially different fitnesses, they must indicate loci that are the source of significant phenotypic variation. Though the relevant phenotypes are generally not known, such loci should be of particular interest in mapping studies of complex traits. For this purpose we have developed a set of SNPs that can be used to tag the strongest â?¼250 signals of recent selection in each population.
Voight, B.F., Kudaravalli, S., Wen, X., Pritchard, J.K. (2006). A Map of Recent Positive Selection in the Human Genome. PLoS Biology, 4(3), e72. DOI: 10.1371/journal.pbio.0040072