Genetic mutation linked to walking on all fours

image: BBC
via Delicious Ghost

Many of you might have seen the BBC/NOVA documentary The Family That Walks on All Fours that aired in 2006. The film profiles the five siblings of a Turkish family with a condition known as Unertan syndrome. This affliction is not only associated with quadrupedality, but also manifests imperfect articulation of speech, mental retardation, and defects in the cerebellum, a part of the brain involved in motor control.

Now, according to Turkish scientists, genetic mutations have been found in four unrelated families (including the above mentioned Ulas family) that are responsible for a protein which is known to be critical to the proper functioning of the cerebellum during development. This finding might put a dent the hypothesis that there is a single gene associated with bipedalism yet might help confirm that there was a genetic component to the transition from quadrupedalism. I'm not really sure how this will bear out in relation to Uner Tan's "backward evolution" hypothesis.

PhysOrg:

Although the families lived in isolated villages 200-300 km apart and reported no ancestral relationships, the scientists expected to find a single genetic mutation implicated in the condition. They were surprised to find that this was not the case.

"We carried out genome-wide screening on these families", said Professor Ozcelik, "and found regions of DNA that were shared by all those family members who walk on all fours. However, we were surprised to find that genes on three different chromosomes are responsible for the condition in four different families.

Here's a snippet from the NOVA documentary:




Passionate Productions - The Family That Walks on All Fours
BBC News - Family may provide evolution clue
Times Online - Life on four legs