Phys.Org has a report on a study of the interbreeding of Homo Sapiens and other species in the past. Interspecies love-ins and the offbeat history of our species. Basically our ancestors seem to have been getting it off with just about any hominid in sight. The inter-species birthrate to allow for the amount of other DNA that has been found is relatively low, so there was probably a fertility problem. Either that or it didn't happen very frequently. Any way it is an interesting insight into our ancestry.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.