Compare this from New Scientist:
The publication of the Neanderthal genome last year offered proof that Homo sapiens bred with Neanderthals after leaving Africa. There is also evidence that suggests they enjoyed intimate relations with other hominins including the Denisovans, a species identified last year from a Siberian fossil. Link.
with Genesis 6:2 The sons of God saw that the daughters of men were beautiful, and they married any of them they chose.
Even if this is not what the Bible is talking about in Genesis - you just never know what scientists are going to turn up!