Make love AND war: Human ancestor Australopithecus used shorter legs for both

William Atkins
Tuesday, 13 March 2007 08:33

Science - Biology

American biologist David Carrier states within his article published March 2007 within the journal Evolution that australopiths had short legs and squat bodies, not just for climbing, but to maintain a center of gravity that was closer to the ground so as not to likely become overturned in fights over women.

The genus Australopithecus (an ape-like human ancestor) came right before the genus Homo—our present classification of modern humans and their close relatives. Only the Homo sapiens species still exist, all other human relatives are now extinct.

The Australopithecus lived between two to four million years ago. Males were short, only about 4 feet 6 inches (137 centimeters) tall, and females only about 3 feet 9 inches (114 centimeters) tall. They had strong forearms and lower legs, robust hands and feet, broad hips, muscular necks, and enlarged heads. They were the first hominids to walk solely on two feet.

During his study, Carrier measured leg length and analyzed indicators of aggression in nine primate species. He compared Australian aborigines (due to their relatively pure ancestry) with eight primate species: black gibbons, bonobos, chimpanzees, dwarf guenon monkeys, gorillas, olive baboons, orangutans, and siamang gibbons.

Carrier found that the longer the hind-limb, the less aggressive was the animal—the shorter the more aggressive. Also, females tended to have longer legs than males, supporting the contention that males did most of the fighting.

He hopes that his research will help humans understand their violent behaviors in the past, which remains still today. His study, along with other similar studies in the past, shows that human violence is related to competition between males. Carrier states within Continuum (the magazine of the University of Utah), “… our high level of violence is something we evolved to be. It’s our nature.”

Carrier also contends that humans did not evolve long, more slender bodies until they invented weapons and learned to fight with them. At which time, they needed to run fast in order to kill their prey with their weapons. Thus, Australopithecus eventually evolved from short to long legs.

From his studies, Carrier comments: “If I argue that humans are by nature violent animals, the concern is that such an argument will be used to justify violent behavior. Although there is some merit to that fear, if our goal is to prevent future violence we need to understand why we are violent animals — where the tendency came from and why it has stayed with us.” [Continuum]