What If the Neanderthals Had Not Gone Extinct?

Neanderthal DNA is 99.7% identical to our own, and researchers claim that some humans might be carrying as much as 2% of the Neanderthal genome. Making things even weirder is that scientists recently recovered a nearly complete DNA sequence from a 50,000-year-old Neanderthal skeleton. So in theory, Neanderthals could make a comeback. But how would they adapt? And how long would they survive?