Humans and chimps shared a joint ancestor as recently as five million years ago. Biologists have long supposed that if they could identify the genes that changed in the evolutionary lineage leading from the joint ancestor to people, they would understand the genetic basis of how people differ from chimps and, hence, the essence of what makes humans human.
Because the sequence of DNA units in the two genomes is 98.8 percent identical, it seemed that just a handful of genes might define the essence of humanity.
The project received a lift two years ago when a large London family with barely intelligible speech was found to have mutations in a gene called FOXP2. Chimpanzees also have a FOXP2 gene, but it is significantly different. The human version shows signs of accelerated evolutionary change in the last 100,000 years, suggesting that the gene acquired a new function that helped confer the gift of speech.
But the process of transforming the joint human-chimp ancestor, who was probably a very chimpanzeelike creature, into a human seems much more complicated in light of the new analysis. In a preliminary screen, Dr. Clark and his colleagues have found that a large number of genes shows signs of accelerated evolution in the human lineage. Those are genes that, by a statistical test applied to changes in their DNA, appear to be under strong recent pressure of natural selection and so are likely to be those that make humans differ from chimpanzees....
The authors of the Science article note that many of the human genes they found to have undergone accelerated evolution turn up in the list of Mendelian diseases, those caused by defects in a single gene. The reason for that curious association could be that the genes serve new functions, ones that emerged so recently that evolution has not had time to install backups, Dr. Clark said...
Staggering. Contrast this article with my post of two days ago on the neuro circuitry that underlies human perceptions of self and cognition. Those circuits are most similar in great apes and humans; since the great apes and we parted paths a while ago this suggests a certain degree of parallel evolution.
Large numbers of genes with a lack of functional redundancy ... Something staggering happened in the past 200,000-300,000 years. Why did homo sapiens alter so quickly? What were the selection pressures? I think the usual explanation is that by that time human population density had risen sufficiently that competition and/or cooperation pressures became intense, and the war of cognition began.
Of course geneticists will not be able to resist the obvious experiments. With a few tweaks here and there, we will create sentient chimpanzees. It might be even easier with the great apes. Since we're eating the great apes at a terrific pace (we probably ate the Neanderthals and Homo Erectus as well) presumably that will be done on zoo bred creatures. After they can talk, we can explain ourselves to them. The chimps will understand, but the great apes may find us a bit off-putting.
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