We now know that the Neanderthals were still around and the Cro Magnons were moving in about 35,000 years ago. There was plenty of time to do these paintings then scamper off to what we now call the Western European Refugia South of the Pyrenees.
We see this same sort of lack of imagination at work with AGW. The Global Warming crowd imagine that Antarctica can melt, the ocean can rise, and everybody will stand around the streets of Miami dumbfounded and drown!
If we give earlier human generations 20 years, that gives us 5 generations per century, so in 1,000 years with 10 centuries, we will have 50 generations. In 10,000 years we'll have 500 generations.
Obviously it only takes 1 generation escaping from the slow-moving ice sheets and glaciers for there to be MANY future generations.
A lot of stuff can go in 1,000 years!