It ought to be fascinating to find out if such vocal characteristics changes over time with upper body strength in the same person (for instance, putting them t

It ought to be fascinating to find out if such vocal characteristics changes over time with upper body strength in the same person (for instance, putting them through a six month strength training program). Or if this is somehow set at puberty, and people's relative strength remained the same over most of their lives. I would imagine most people don't suddenly acquire an urge to become stronger after they reach their thirties. Or at least they didn't while humans were evolving.