A very interesting video explaining how and why people used to walk differently. Essentially, it is explained, now we walk heel-first because it is easier and safer to do so. Five centuries ago and more, people wore shoes that were more like leather socks and to step forward they used the ball of the foot first to make sure they don't step on something that might hurt them.
It is very interestingly related to medieval depictions of people doing various things in strange, for us, postures.