Plus look at toddlers and some Asian cultures. They can squat full dept with no problem. My toddler can squat and stand up without issue. I can - but I've retrained myself and opened up my hips/hamstrings and worked on core strength. baby's mama cannot perform a full depth squat let alone with any weight on the or front rack position. The old Asian lady down the street can and does when she does her gardening.

I think that coupled with a lot of people have at least mild APT because of a weak core is the major issue. It causes hip strain.

I wouldn't be surprised if most of that flexibility in Asian cultures comes from using a squat toilet (or open defecation) everyday.