Neanderthals were smarter than most people think.

A study of Mousterian (Neanderthal-associated) stone tools shows some were fitted with handles via a carefully crafted glue made of bitumen and ochre. Both ingredients occur naturally, but not in combination.

If you get the mix right (and the researchers had to experiment) you get a handy glue of the right tackiness to stick to the tool but not to the skin. A bit like half-wrapping a razor blade in Blue Tack.