Selecting for Humans

Frans de Waal / Emory University

The paper:

The finding:
Rasmus Nielsen from the University of Copenhagen and colleagues from Cornell University compared 13,731 human genes to their chimpanzee orthologs and found the strongest evidence for positive selection in both genomes among apoptosis genes and tumor suppressor genes. Genes expressed in the brain showed little or no evidence for positive selection. "We're really forming a very complete picture of the way natural selection has formed the genomes of the species we're looking at," Nielsen says.

The significance:
Molly Przeworski at the University of Chicago says that with the genome-wide variation data, "we'll be able to detect other kinds of selection," which will lead to better evolutionary insights.

The surprise:
Nielsen says he was surprised that, in the brain, "when you look at protein-encoding genes, we're much more similar to chimpanzees there than we are in the other categories of genes," such as those in testis, liver, blood, or kidney.

The catch:
"They detect one particular type of selection, but we don't know how frequently selection acts that way," Przeworski says. James Sikela at the University of Colorado Health Sciences Center says copy number variation, for example, "would be another way that evolution could work to make important changes in genomes, which would be important in, let's say, brain function."