From: Anna Salleh, ABC Science Online
Published June 30, 2010 09:00 AM

Human Bite Stronger Than Thought

Humans have a much more powerful bite than previously thought, thanks to the mechanics of their skull, say Australian researchers.

Stephen Wroe from the University of New South Wales in Sydney and colleagues reported their comparison of human and other skulls recently in the Proceedings of the Royal Society B.

"The traditional view is that modern humans have lost the ability to generate a powerful bite," said Wroe.


He said this has been driven by the fact that humans have relatively weak jaw muscles and lightweight skulls, compared to our fossil ancestors and living great apes.

Some scientists argue a weaker bite evolved in response to humans eating softer foods, processing them with tools and cooking.

But, said Wroe, there has been no direct data to support these conclusions. He said the very thick tooth enamel coating human teeth is generally associated with processing hard foods in primates.

Wroe and colleagues used sophisticated engineering software to compare the maximum bite force of modern humans with that of four living apes (chimpanzee, gorilla, orangutan and gibbon) and two fossil hominids (Australopithecus africanus and Paranthropus boisei -- also known as "nut-cracker man").

They used a method called 3D finite element analysis to study digital models of skulls that had been CAT-scanned.

The researchers simulated a scenario in which the animal was biting a hypothetical hard object with its back teeth, and visualized how stress was distributed.

"When you actually look at the mechanics of it, the human jaw is highly efficient," said Wroe.

"For any given bite force you want, we can achieve it with much less muscle."

The researchers say the design of the human jaw makes it 40 percent to 50 percent more efficient than for all great apes.

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