Signs of selection in our genes

Humans and chimpanzees have been diverging for around 5 million years, during which time they've acquired major anatomical and cognitive differences, but New York–based researchers report this week in PLoS Biology that some of the strongest evidence of positive selection since divergence is seen in genes that relate to immunological defense and apoptosis.

Building on an earlier study, Cornell University's Rasmus Nielsen and colleagues compared over 13,000 annotated human genes and their chimp equivalents, using the ratio of synonymous to nonsynonymous mutations as evidence of positive selection. Their aim, Nielsen said, was to determine "which genes have been changing as humans and chimpanzees have evolved into their modern forms."

The team subjected orthologous human–chimp gene pairs from published human data and polymerase chain reaction data obtained from a single male chimpanzee to likelihood analysis, which revealed any differences in mutation type ratio. They excluded genes with fewer than three nucleotide ...