Leaving aside for the moment the question of gender roles, I've been coming to the conclusion that studies of the origins of humans still underestimate the importance of speech. What they miss is that speech doesn't just communicate within the group: it communicates across time. It allows culture to accumulate and grow, and that, in my opinion, is what makes the difference between humans and smart apes. It might be all it takes to explain the huge technical difference between humans and Neanderthals, and why some other pre-humans with brains almost as big as ours never got past the cracked-stone-blade stage of tool making.

Because when you look at it critically, one human's cleverness doesn't amount to all that much. Put a naked ignorant human down in a chimp or gorilla tribe and he couldn't do much better than the rest of them, for all his big brain. Even the inventor of Tarzan, writing pure fantasy, had to cheat by giving him European culture in the form of tools and books to make his achievements believable.

If you can share a discovery, a better way of doing things, you can pass it on, so the next generation can build on it instead having to invent it all over again. That's how you go from twisting creepers into a basket, to making nets so you don't need the whole tribe to turn out to corner one beast and weaving cloth good enough to make the cold North habitable. One of the most credible explanations I've heard for our anomalously long lifespan is that old people's knowledge was an asset to the tribe, long after they were useless as breeders and food providers, and getting too weak for childcare.

That's why the making of complex artifacts seems to come out of nowhere, with no visible change in the remains of the people making it. Because culture builds exponentially: slow development of the basics, till you reach a stage where ideas come together and techniques reach perfection, and suddenly it takes off and people watching from a distance say "Where did that come from?"