The body can pose many puzzles for us, but one of the most intractable ones for me is "what to do with the shoulders?"
The hip joints are so easy by comparison: either the upper ends of your legs are snugly in their ball-and-socket joints (no problem) or they are not (problem).
But our shoulder joints have evolved radically differently. In order to allow both our arms to hang from us and us to hang from our arms, the shoulders offer a compromise of flexibility and stability. The simple shoulder shrug is the gestural manifestation of that.
In this discussion with Vivien Mackie she helps me to elucidate an answer, and given how prevalent shoulder issues are, I think it's worth a watch!