[Coyoteman]

So far as I know, the geneticists have never had Neanderthal tissues to work with. Conclusions seemed to be based on computer models.

There have been upwards of five mtDNA sequences, and I think one Y sequence, established. Most of these samples are from teeth, which are great vessels for preserving DNA. So, its not just computer models.

[RobbyS]

Then it is still highly speculative. However, I am willing to accept if they have also make a determination about the DNA of extinct beasts like the Sabertooth tiger.