Animation began with a model of Australopithecus

The way chimpanzees move, though, is quite different from us. Their knees are always slightly bent, and they lean forwards at the hip to compensate for this. So, did Australopithecus move like us - or like them?

Well, neither - according to the work of Dr Robin Crompton and his team at Liverpool University, UK. The legs and pelvis of Australopithecus were quite different from ours, but also different from chimpanzees'.

Analyses of which muscles are used in the different ways of walking showed that Australopithecus would neither have been able to walk upright in the way a chimpanzee does nor the way we do. Instead, Dr Crompton found that there was another modern ape that occasionally walks upright and was a much better match for how Australopithecus may have moved - the orang utan.

Bent knees

Orang utans live almost exclusively in the trees, but that does not stop them from occasionally walking on two legs. Rather than walk on the ground, they walk along branches, steadying themselves by holding on to other branches with their hands. The way they walk, with straight legs and very little bending at the knee, might be a much better model for Australopithecus.

These early hominids faced many threats

So, the animators on Walking With Beasts worked with Dr Crompton to try to get Australopithecus moving on the screen in as realistic a way as possible. It may look strange to us, because it is unfamiliar, but other scientists who have watched the movement describe it as "startling" to see all their theories put to the test and come out as successful.

We may never know if this is how Australopithecus really looked, but it would certainly have been possible, given their skeletons, and would even have been energetically efficient over short distances.

Why do we walk so differently, then? Dr Crompton's work on early humans suggests that modern humans have evolved a way of walking that is more efficient than that of Australopithecus when we are carrying things in our hands.

Walking With Beasts is broadcast in the UK on BBC One on Thursday, 15 November, at 2030 GMT.