From National Geographic:
The study suggests that the human and chimp lineages initially split off from a single ape species about ten million years ago. Later, early chimps and early human ancestors may have begun interbreeding, creating hybrids—and complicating and prolonging the evolutionary separation of the two lineages. The second and final split occurred some four million years after the first one, the report proposes.
“One thing that emerges [from the data] is a reestimate of the date when humans and chimps last exchanged genes,” said David Reich, a professor at Harvard Medical School’s Department of Genetics in Boston.
More here.