4 mars 2016

Le visage a-t-il évolué pour encaisser des coups?

Ton visage est-il le résultat d'une évolution qui lui permet de mieux encaisser les coups? C'est ce que suggère cette étude:

(...) "It turns out that the parts of the face that became stronger were the parts of the face that most frequently break when modern humans fight," study author David Carrier, professor of biology at the University of Utah, told Live Science. "These are also the parts of the face that are most different in size and shape between males and females in both Australopiths and Homo." (...)

Watch any boxing match, bar fight or any other bout that pits humans against each other in hand-to-hand combat, and it's clear the face is usually the primary target. Studies on assault have shown that not only is the face targeted the most, it also often takes the most damage. A study published in 1990 in the Journal of the Royal Society of Medicine, and completed in the United Kingdom, found that 83 percent of all fractures sustained during an assault were facial fractures.

(...) In the study published this month in the journal Biological Reviews, Carrier and Morgan reviewed a large number of studies on primate facial structure. They found that as hominids evolved the jawbone in particular became larger and broader than in other primates, the cheekbones became larger and thicker, and the bones around the nose and eyes became thicker.

This "protective buttressing" hypothesis builds on earlier work from Carrier and Morgan that also suggests human anatomy is the product of early violence. (...) Hand bone structure that would allow a fist to form was first seen about 4 million to 5 million years ago, Carrier said. This is also the same time that humans started developing larger and thicker facial bones. 

Their research challenges a 60-year-old hypothesis that the dense facial structure of human ancestors evolved to help them chew hard foods like nuts or coarse grasses. However, after looking at the wear on Australopith teeth, some researchers have concluded that their diet likely contained very few hard-to-chew foods. Carrier and Morgan proposed an alternative explanation.

Still, other anthropologists, like Andrew Kramer, paleoanthropologist at the University of Tennessee, remain skeptical of the new hypothesis and believe that diet is still the more likely explanation.

(...) But Carrier and Morgan said the classical diet theory does not explain why males have larger facial bones and jawbones than females do, because the diets for both sexes were very similar. Most tussles happen between males, and that might explain why they have larger, stronger facial bones, and why studies show jaw muscles in males are 34 percent stronger than they are in females.

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