There is an exercise thing about Marathon runners, that Blue Collar workers find it easier to train. They basically have to do less, and have better results. What they worked out was because they are exercising all day at work, they have better heart rates.
Also one of the big movements in fitness is for want of a better word the '300' systems. Not really fair to call them that, but easier for everyone if I do. It feeds into what we are discussing really well, actually. What they have found is, if you want to be real world strong, or fit, do real world things. Sounds like a Doh! moment, but what actually happened was a US Judo coach went to find out why the Russians keep owning them, and discovered kettlebells. Which are basically dumbbells, but the weight can move and is not centred over the hand. The whole point of this and why it ties in here is that they found that all of the high tech equipment trains the big muscles, ignoring the small ones. The small ones are important for stability.
So why can a native pick up large weights and move them, and we struggle, because he did it yesterday, the day before, and for most of his life. Why can he do it barefoot, because he has never worn shoes for any length of time, so all of those muscles, and toughing we need, he has had a lifetime head start on.