But I personally think they couldn't handle the weather change. And my former BIL is just a hold-over.
/johnny
Finding the most recent Neanderthal traces so far north would seem to back that up. It's possible that Neanderthals followed the glaciers north as they receded.
As far as I know, the Neanderthals never developed anything that could be called “art.” And by the same token, no indications of any religion.
But the fact that they were unable to conceive of projectile weapons (throwing spears, arrows, darts, slings, boomerangs, etc.) is highly indicative of a fundamental difference in their brains.