Sunday, August 16, 2009

Tree-climbing or Knuckle walking? That is the Question.

Up until this week, the assumption was that homo sapiens evolved from a knuckle-walking primate ancestor.  It seemed logical enough.  Two of our wrist bones fused, thereby making it easier for our ancestors' gate to be more stable while knuckle-walking.  But this week, the shattering news reached those of us interested in primates.  
Knuckle-walking?  Not so!  According to a new study published by Tracy Kivell and Daniel Schmidt, Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestors.  Homo sapiens, they say, descend from a tree-climbing ancestor who then came down and evolved to bipedalism.
As a matter of fact, the authors argue the data they collected would indicate knuckle-walking evolved twice - thereby placing chimpanzees and bonobos in a different knuckle-walking category than gorillas.  They found that the wrist bone structure of gorillas is very different from that of chimpanzees and bonobos, our closest relatives.
Gorillas spend more time on the ground and in trees.  This, Kivell and Schmidt argue, would tend to indicate that our far away ancestor was a tree-climbing ape rather than a knuckle-walking one.

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