Them's fightin' legs

Elizabeth Pennisi has a short piece in Science describing David Carrier's ideas about leg length and fighting in early hominids.

David Carrier, a comparative physiologist at the University of Utah in Salt Lake City, has jumped into the fray with a provocative idea about Lucy's legs. In earlier studies with dogs, he had found that short legs provide mechanical benefits during fights. Pit bulls' short limbs, for example, aid stability and are tough enough to sustain attack without breaking.
Carrier contends that Lucy and other australopithecines also had bodies built for defense against each other: Their short legs may have provided a competitive edge when males battled rival suitors.

This is basically the wrestler vs. distance runner physique story. And it could be true -- but is it a primary cause or a secondary one? Depends how they were fighting, I should think.

The interesting part is that it is not an argument based on optimal energy expenditure. But is it safe to use sexual dimorphism as a proxy for male competition? And were australopithecines really very sexually dimorphic?

Boy, there sure seem to be a lot of unknowns lately.

References:

Pennisi E. 2006. Was Lucy's a fighting family? Look at her legs. Science 311:330. Full text (subscription)