When I wrote this I gave a first draft to my sister to read. She objected vociferously to my postulate that early humans, pre-civilization, had anything even approximating agriculture, ever planted anything in the ground and tended it.. She still does, and I know I'm going beyond what received wisdom is about these people. But I'm not real good at receiving others' "wisdom" when it flies in the face of what I consider logic, and to me this does. I refuse, as you've already seen, to entertain the proposition that early humans were intellectually inferior to us modern folks; there's no evidence in paleontology that brain size or capacity has significantly changed since what I've set up as Hugo's time, and the capacity to think creatively and to learn shouldn't have changed all that much, either. Since simple observation would allow Hugo's compatriots to see the basics of plant reproduction and sustenance, and it's only a small step beyond to begin purposefully growing things in collective gardens. We're not talking beyond that; the inability of small groups to set up long-term settlements would preclude more than casual gardening. (There's a good bit more about this later in the novel, in some more detail.) But why should hunter-gatherer groups have been limited to what simply sprouted up by chance nearby?
I mean, when agriculture arose in greater concentration around 10,000 years ago or so, did it actually spring into being from nothing? Or was the notion of cultivating plants a long-standing and established one, which ultimately gave rise to fixed population centers as humans increased in number and required greater stability of food supply? I lean pretty strongly toward the latter, as this novel should tell you.
Hugo's good health, including dental, shouldn't be a huge surprise. Illness or a propensity toward it wouldn't have been a big survival trait in a time when the odds of a pregnancy producing, in time, a living adult were pretty damn small. So the fact that Hugo became a fully grown man alone says he had to be pretty healthy, and reasonably resistant to disease.