[floriol]

Doesn't it have to do something with the "average" primate body plan? I really like highlighting the running aspect, since we truly seem to be record holders in endurance running, which was largely enabled by sweating. And since the primate body plan has upper limbs with significantly more freedom of motion compared to "running on 4" animals like deer, primates have to actively use many muscles to be able to put its weight on them (I am only familiar with the human skeleton in detail, but I assume primates have a similarly free scapula, while horses' are much more restricted, their first legs connect nearly vertically into it, making standing basically energetically free)

So, isn't bipedalism simply the energetically better way of locomotion for the primate body plan (look at other primates, they semi-walk on their lower limbs, only balancing with their hands - but they are not great at running and live mostly on trees so climbing is more important there)?