Saturday, July 19, 2014

Devolution discredited

A 2006 BBC documentary entitled “The Family That Walks on All Fours” shows 5 siblings living in a remote area of Turkey who are unable to walk upright (CLIP HERE, IMAGES HERE). They have an inherited condition called Uner Tan Syndrome (UTS) and they are used to illustrate a theory developed by its discoverer, neuroscientist and evolutionary biologist Ûner Tan of Turkey's Cukurova University, that people with UTS are a human model for reverse evolution - “devolution” – and offer insights about how our predecessors transitioned from 4-legged to 2-legged walking. In a newly published study by American anthropologist Liza Shapiro of the University of Texas at Austin shows that the family and others with UTS have simply adapted to their inability to walk upright and do not represent an example of backward evolution. She does this by showing that the study subjects walk in a lateral sequence (placing a foot and hand down on one side and then the other), while apes and other nonhuman primates walk in a diagonal sequence (placing a foot down on one side, then a hand on the other side, and continuing in that pattern). Shapiro sums up, "As we have shown, quadrupedalism in healthy adults or those with a physical disability can be explained using biomechanical principles rather than evolutionary assumptions.”

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