20,000 years ago

I'm just thinking what would happen if I accidentally walked through a time portal and went back in time 20,000 years? Would I eventually meet other human beings? Would they be hostile? Would they think I'm strange? What would my life be like?

Not that I believe that backwards time travel is possible; indeed, I believe it's metaphysically impossible. But I might be wrong, and besides, it's interesting thinking about such things.