Recent genetic studies indicate ancient humans interbred with at least three known and possibly one unknown hominid species. This interbreeding went on for thousands of years in a possibly back and forth gene exchange between the species.. http://www.sciencedaily.com/releases/20 ... 133658.htm
Family tree of the four groups of early humans living in Eurasia 50,000 years ago and the lingering genetic heritage due to interbreeding. (Credit: Image courtesy of University of California - Berkeley)
Neanderthal Genome Shows Early Human Interbreeding, Inbreeding
Dec. 18, 2013 — The most complete sequence to date of the Neanderthal genome, using DNA extracted from a woman's toe bone that dates back 50,000 years, reveals a long history of interbreeding among at least four different types of early humans living in Europe and Asia at that time, according to University of California, Berkeley, scientists.