Reply #18: Not necessarily true

[semillama]

Cross-species breeding is possible, as any birdwatcher will tell you. If two species are closely related enough, fertile offspring are possible.

The problem is that we lack adequate samples of Neandertal DNA to compare with our own. It's entirely possible that the DNA lines of mixed Neandertal/Cro-Magnon breeding have been extinguished, due to chance (That is, a line of people with such a genetic heritage failed to reproduce enough and the gene line extinguished.)