Tech Shout!

A study conducted by the University of Utah has concluded that ape-like human ancestors (australopiths) had short legs for around 2 million years because a squat physique and stance helped the males fight over access to females.

According to David Carrier, a professor of biology, “The old argument was that they retained short legs to help them climb trees that still were an important part of their habitat. My argument is that they retained their short legs because short legs helped them fight.”

For those who are unaware about their ancestors namely those creatures of the genus Australopithecus, well, they are the immediate predecessors of the human genus Homo. These pre-human creatures had heights of about 3 feet 9 inches for females and 4 feet 6 inches for males. They lived around 4 million to 2 million years ago.

Carrier said, “For that entire period, they had relatively short legs-longer than chimps’ legs but shorter than the legs of humans that came later.”

“So the question is, why did australopiths retain short legs for 2 million years? Among experts on primates, the climbing hypothesis is the explanation. Mechanically, it makes sense. If you are walking on a branch high above the ground, stability is important because if you fall and you’re big, you are going to die. Short legs would lower your center of mass and make you more stable.”

In spite of this, Carrier has said that his research suggests short legs helped australopiths fight because “with short legs, your center of mass is closer to the ground. It’s going to make you more stable so that you can’t be knocked off your feet as easily. And wit short legs, you have greater leverage as you grapple with your opponent.”

Carrier has compared the australopiths with all modern great apes such as humans, chimps, orangutans, gorillas and bonobos, who engage in at least some aggression as males compete for females.

Carrier compared the Australian aborigines with the eight primate species namely gorillas, chimpanzees, bonobos, orangutans, black gibbons, siamang gibbons, olive baboons and dwarf guenon monkeys.

“Given the aggressive behavior of modern humans and apes, we should not be surprised to find fossil evidence of aggressive behavior in the ancestors of modern humans,” Carrier says. “This is important because we have a real problem with violence in modern society. Part of the problem is that we don’t recognize we are relatively violent animals. Many people argue we are not violent. But we are violent. If we want to prevent future violence we have to understand why we are violent.”

“To some extent, our evolutionary past may help us to understand the circumstances in which humans behave violently,” he adds. “There are a number of independent lines of evidence suggesting that much of human violence is related to male-male competition, and this study is consistent with that.”

Nevertheless, male-male competition doesn’t fully explain human violence, Carrier says, noting other factors such as hunting, competing with other species, defending territory and other resources, and feeding and protecting offspring.