Two things today:
First, alcoholic beverages. Distilling was of course a long way in the future in prehistoric times, but fermentation wasn't. It's a natural process, so it seems likely that early humans quickly discovered the intoxicating properties of such as fermented fruit juice, etc., and even ways of producing it deliberately. There's even a modicum of evidence of this during the earliest historic period.
Second, where did these early humans live? Popular thinking is that they made their homes in caves, and perhaps some did, but humans inhabited a wide range of terrain, whereas natural caves of any habitable dimensions are available only unusually and in limited areas. In addition, caves certainly have drawbacks as residential properties. There's some archaelogical evidence of constructed dwellings in some areas. And it would scarcely have been beyond their capabilities; I mean, even birds and some amphibians build nests, not to mention many mammals. I think of Hugo's people as sufficiently industrious to erect their own shelters, which should not have been a problem with societal cooperation.
Over the course of writing this I put a lot of thought into the living circumstances I felt were most likely for early humans. There's a good bit more of this toward the end of the story. Some readers have argued with me about some of my hypotheses that go beyond conventional thinking, and perhaps they're right. But I think there's enough rational support for my approaches that I can reasonably ascribe them to the prehistoric world of my imagining.