“Anyone who cannot cope with mathematics is not fully human. At best he is a tolerable subhuman who has learned to wear shoes, bathe and not make messes in the house.”

I’ve seen the louse genetics figure before. The date is consistent with the out-of-Africa hypothesis than humanity originated in east Africa about 100,000 years ago. Of course it depends on what you mean by “humanity.” Most scientists use the word “human” loosely to refer to any bipedal primate, even for creatures like Neanderthals that everyone now agrees could not have been human ancestors. If by “human” you mean homo sapiens sapiens, it looks like humans wore clothes from the beginning.

Heinlein had a thing for solving equations. IIRC one of his ideas was to require a voter to solve a quadratic equation before they could vote.

If I’ve got my dates straight, when he was growing up the USA was much less specialized than it is now — a large proportion of the population lived on family farms, and were pretty self-sufficient. I can’t recall if he grew up on a farm, but I know he served in the Navy. Between farming and serving in the Navy you’d have most or all of those skills down. Still pretty specialized though, compared to a totally self-sufficient animal.

To the list I’d add starting a fire in the rain, to start.

Looking at what we’ve learned from the “ice man” is a fascinating glimpse into paleolithic life. And louse genetics indicate we’ve been wearing clothes for only 78,000 years or so. I think we got specialized pretty soon after we started living in cultures. Evolutionarily speaking, developing that kind of cooperation is and specialization is exceedingly rare, and has only happened 14 times or so in the history of life on Earth. I think all but one of those times were in insects. Some folks think that society and specialization, more so than intelligence, bipedalism, pair bonding, tool use, brain size, opposable thumbs and the rest is the hallmark of humanity and the reason that we have been so successful as a species. It may also explain why we haven’t heard much from life on other planets.

So maybe specialization is for humans and insects — but not the rest of life on Earth. And I think humanity is the only species that doesn’t use genetic determinism, but culture, for specialization.