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Humans bite different from gr.apes/apiths

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  • Marc Verhaegen
    http://www.sciencedaily.com/releases/2010/06/100622095116.htm The robust jaws & formidable teeth of some of our ancestors and ape cousins may suggest that
    Message 1 of 1 , Jun 30, 2010
      http://www.sciencedaily.com/releases/2010/06/100622095116.htm

      The robust jaws & formidable teeth of some of our ancestors and ape cousins
      may suggest that humans are wimps when it comes to producing a powerful
      bite: but a new study has found the opposite is true, with major
      implications for our understanding of diet in ancestral humans.
      The surprise findings suggest that early modern humans did not necessarily
      need to use tools and cooking to process high-nutrient hard foods, such as
      nuts - and perhaps less tough foods such as meat - but may have lost an
      ability to eat very tough items, such as tubers or leaves.
      In the first comparison of its kind, Australian researchers have found that
      the lightly built human skull has a far more efficient bite than those of
      the chimp, gorilla and orang-utan, and of two prehistoric members of our
      family, Australopithecus africanus and Paranthropus boisei.
      They found that modern humans can achieve relatively high bite forces using
      less-powerful jaw muscles. In short, the human skull does not have to be as
      robust because, for any given bite force, the sum of forces acting on the
      human skull is much less.
      These results also explain the apparent inconsistency of very thick tooth
      enamel in modern humans - a feature typically associated with high bite
      forces in other species. Thick enamel and large human tooth roots are well
      adapted to take high loads when biting.
      The study appears in a paper in the journal Proceedings of the Royal Society
      B by a team led by Dr Stephen Wroe, of the Computational Biomechanics
      Research Group in the UNSW's School of Biological, Earth and Environmental
      Sciences ...
      These result calls into question previous suggestions that the evolution of
      a less robust skull in modern humans involved a trade-off for a weaker bite
      or was necessarily a response to behavioural changes, such as switching to
      softer foods or more processing of foods with tools and cooking. It has also
      been suggested that human jaw muscles were reduced to make way for a larger
      brain.
      "However plausible those ideas may seem they have been based on very little
      by way of comparative data: for example, there are no actual records of bite
      force collected from living members of any other ape species, " says Dr
      Wroe. "It turns out that we don't have a wimpish bite at all - it is very
      efficient and powerful.
      "When we're biting down in vertical plane, at the back of the jaw our bite
      is about 40-50% more efficient than it is for all great apes. It's even more
      efficient when biting at the front of the jaw.
      "We've only looked at two extinct hominins in this study, but, for our size,
      we humans are comparable in terms of maximum bite force to these fossil
      species, which include 'nutcracker man', renowned for its particularly
      massive skull and jaw muscles. Size matters, but efficiency matters more -
      and humans are very efficient biters ...


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