This is interesting to ponder... It could be that their "lifestyle" became obsolete. (like hopefully the 1% of the richest humans will one day). In other words, some kind of food source they relied on may have become extinct, dooming the species, esp. in winter. Like Mammoths. Sorta what happened to the Native Americans when Buffalo Bill decided to kill every fucking buffalo roaming free, so the natives would have nothing to live on. And we see what happened to them in just a couple of hundred years. And if they didn't have other sources of food (provided by white men), they would've perished. Yes, I can see Neanderthals living like Native Americans, off the land, eating the most abundant species, which suddenly disappears... In fact, maybe the Neaderthals had it down, living for 10's of thousands of years in harmony with the Mammoths, not taking too many. Then one day along comes HUMANS, who figure out a way to take out whole herds of Mammoths, perhaps by driving them off a cliff with fire or some such, thus decimating the population which might never have recovered. So perhaps HUMAN GREED, demanding far more than they needed to survive (just like today), caused the demise of both the Mammoth and the Neanderthal. Hell they wouldn't even have had to fight the Neanderthals, just destroy their primary food source, and you win! Now there's a scenario I can see happening and setting the stage for where we are today... Perhaps we, the 99%, are just like Neanderthals, in the process of extinction by the 1% due to their excessive greed.