I wouldn't say entirely that they "didn't survive" considering we're talking about their genes existing within humans today. Also, long term survival of a spec

I wouldn't say entirely that they "didn't survive" considering we're talking about their genes existing within humans today. Also, long term survival of a species has a lot more to do with luck than you'd think. e.g If cooling temperatures killed off their primary food source and forced them to migrate into human controlled territory where they didn't have experience, they'd be at a disadvantage. But if they lived in a temperature warming era, we may be having the opposite conversation right now. "Guns, Germs, and Steel" is a good summary of this hypothesis.