Apparently, our ancestors and chimps just couldn’t keep their hands off each other:

The researchers, from the Broad Institute of MIT and Harvard, propose that humans and chimpanzees first split up about 10 million years ago. Then, after evolving in different directions for about 4 million years, they got back together for a brief fling that produced a third, hybrid population with characteristics of both lines.

That genetic collaboration then gave rise to two separate branches, one leading to humans and the other to chimps.

This will no doubt drive the creationists ape.

[Via The Speculist]