The skeleton of Lucy, the best-known example of the hominid Australopithecus afarensis, shows that its owner probably got around on two legs. But it is not at all clear what gait was preferred. Was it chimpanzee-like? Or the related ‘bent-hip, bent-knee’ carriage that humans can use but normally don't (as seen in exaggerated form in films featuring Groucho Marx)? Or erect, like that of modern humans?

Robin Crompton and colleagues have tackled these questions by assessing the biomechanical effectiveness of a numerically simulated model skeleton of Lucy, and testing it under various assumptions (Journal of Human Evolution 35, 55-74; 1998). Among the results are the screen dumps shown here, which come from animations run by the authors. They show Lucy with ‘motion functions’ derived from erect human walking (top) and bent-hip, bent-knee walking.

figure 1

Figure 1

Crompton et al.rule out a chimpanzee-like gait. They also conclude that bent-hip, bent-knee motion is so much less mechanically effective, and heat generation so much greater, that an erect carriage was favoured. Lucy, they believe, walked tall.