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.Ī prominent set of accelerated human genes are those involved in hearing, particularly the gene that makes a protein called alpha-tectorin, a component of the tectorial membrane of the inner ear. Clark and his colleagues have found that a large number of genes shows signs of accelerated evolution in the human lineage. 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.īut 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. Chimpanzees also have a FOXP2 gene, but it is significantly different. 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. 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.īecause 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. Humans and chimps shared a joint ancestor as recently as five million years ago.
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