I can’t attest to the entire past, but my ancestors on both sides were farmers or construction workers. They were fit. Heck, my dad has a beer gut at 65 but still has arm muscles that’ll put me to shame — someone lifting weights once a week. I’ve had to do construction for a summer and everyone there was in good shape.

They don’t go to the gym, they don’t have the energy; the job shapes you. More or less the same for the farmers in the family.

Perhaps this was less so in the industrial era because of poor nutrition (source: Bill Bryson, hopefully well researched). Hunter gatherer cultures that we still study today have tremendous fitness (Daniel Lieberman).