It ia still happening just watch the YT clips.
Animals still cant sweat and since the average height of human increased. We prolly have longer legs now.
Which should allow us to run faster. And yes a lot of folks have bad diets now. However there are still enough people who eat pretty healthy
And back then life was far from perfect. Life expectations are much higher now. So maybe there werent fitter perse but much more determine to hunt or find food.