Context, context, context

A recent paper in PLoS Biology, A scan for positively selected genes in the genomes of humans and chimpanzees, is bouncing around the evolution blogosphere (ok, I don’t like the word blog, but I digress…). The paper, by Rasmus Nielsen et al, shows that since the divergence of humans and chimpanzees positive selection has acted most strongly on genes associated with spermatogenesis and cancer. Genes that we might expect to show many differences, such as those with maximal expression in the brain, show little evidence of positive selection.

Mike the Mad Biologist argues that Nielsen’s method may be missing a lot of genes responsible for differences between the two species.

However, even if there aren’t many changes in the genes—these macro-molecular forms—there are still many differences in the developmental contexts in which these types of organisms exist. Remember, genes don’t do anything outside of a specific expression, so even the same ‘gene’ that has the same ‘function’ might have quite different large scale consequences for the organism.