since million years, human go at the gym and lift regular weights to get really strong, it's well known, how else would they do? They also eat protein mixtures
I don't know how Neanderthals got strong but I'm not sure they had a lot of rocks to carry regularly.
and the "results" are a bit artificial as well, what matters is a strong core, legs, arms, but not the useless volume you get when lifting, because that's not a movement we do in our daily lives, we rather do small movements, static pauses, small weights. Better training for the right purposes