I don’t have any citations, but I don’t think that “work” was at all similar to what we do now. Early hominid work would have involved many different tasks throughout the day, such as tracking, hunting, cleaning, gathering, building, repairing, traveling, etc, right? Compare that to “do this one task 8-16 hours in a row,” and it does seem like a mode of work we would be particularly ill suited for. Orrrr maybe I’m wrong, I’m using general knowledge and inductive reasoning, so I would not be suprised to learn I’m off base here.