I remember an illuminating lecture from Ray Anthony back in the mid '90s (I'm sure your rember too Ray) where he told us that foot problems really developed when man invented the wheel and needed hard flat surfaces for them to run over.
That's why of course the foot is designed to be a mobile adaptor for the undulating surfaces we're all should walking on.
So now here's the research to prove it.
Their conclusion is wrong because these guys as we all know clocked up a lot more walking and standing time while doing their hunter garter thing.