Human Quadrupeds

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Human Quadrupeds

Post by Snookems » Fri Apr 07, 2006 1:49 pm

Human Quadrupeds

It sounds like something from an old-style circus: Four sisters and a brother who have walked on all fours since childhood. But it's gotten some scientists excited that the siblings could provide a clue to our evolutionary past. And the BBC is jumping in with a special, airing 17 March, on "the first human quadrupeds the modern world has ever seen."
The five are now young adults in a family of 19 living in a village in southern Turkey. Scientists from the nearby University of Cukurova began studying them in2004. Physiologist Uner Tan found that they are mentally retarded, with very limited vocabularies, and brain scans revealed atrophy in the cerebellum, the brain's motor area. A German-Turkish team published a DNA study online in the Journal of Medical Genetics in December 2005 that maps the quadrupedal trait to a particular locus on chromosome 17.

In a paper in the March International Journal of Neuroscience, Tan postulates that the syndrome represents "a backward stage in human evolution" and may cast light on how speech and bipedality coevolved. Because the siblings walk on the palms of their hands, rather than on their knuckles, like apes, Tan hypothesizes that our hominid ancestors were palm-walkers.

Researchers at the London School of Economics (LSE), who have also examined the family, have come up with a less dramatic interpretation. Evolutionary psychologist Nicholas Humphrey and colleague John Skoyles believe the condition is the result of a highly unlikely combination: cerebellar atrophy (which alone would not prevent bipedalism) and the whole family's unusual penchant for "bear walking"--using hands and feet instead of the usual knee crawl--in infancy. The LSE team brought in a physiotherapist, who was quickly able to teach the hand-walkers to walk upright. Nonetheless, Humphrey says the phenomenon could indeed supply "a model for how our ancestors might have walked."

Antharopologist Owen Lovejoy of Kent State University in Ohio throws cold water even on this idea, saying "people have been debating ancestral palm-walking for more than 100 years, but its emergence with this type of cerebellar dysfunction in modern humans does nothing to advance the argument."



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