Something people never seem to understand is that humans, homo sapiens, have hardly changed since we became HOMO SAPIENS. We are the same species, albeit with some variance the depends solely on the environment we live in. Currently humans are stronger, taller, more adept in combat, and healthier (the better among us at least) than at any point in human history. Do you think grug from 25 000 years ago spent his entire day doing this gruelling shit you imagine him to? Or do you think he was a HOMO SAPIEN who when he killed the mammoth, sat down and was as lazy as he was allowed to be? Do you really think he spent hour of his day training in any regard, for anything in specific, or do you think he did what he needed to do, the bare minimum, and fucked off after that?