Turkey: Mutation causes siblings to walk on all fours

[Emu]

http://news.bbc.co.uk/1/hi/sci/tech/4782492.stm

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Family may provide evolution clue

Five siblings from Turkey who walk on all fours could provide science with an insight into human evolution, researchers have said.

The four sisters and one brother could yield clues to why our ancestors made the transition from four-legged to two-legged animals, says a UK expert.

But Professor Nicholas Humphrey rejects the idea that there is a "gene" for bipedalism, or upright walking.

A BBC documentary about the family will be shown on Friday 17 March.

Professor Humphrey, from the London School of Economics (LSE), says that our own species' transition to walking on two feet must have been a more complex process that involved many changes to the skeleton and to the human genetic make-up.

However, a German group says a genetic abnormality does seem to be involved in the siblings' gait.

Coordination problem

Three of the sisters and one brother have only ever walked on two hands and two feet, but another sister alternates between a bipedal and quadrupedal gait. Another brother walks on two feet all the time, but only with difficulty.

The siblings live with their parents and five other brothers and sisters. They were born with what looks like a form of brain damage.

MRI scans seem to show that they have a form of cerebellar ataxia, which affects balance and coordination.

However, scientists are divided on what caused them to revert to quadrupedalism (walking on all fours).

The method of locomotion used by the Turkish children and by our closest relatives chimpanzees and gorillas, differs in a crucial way, said Professor Humphrey.

While gorillas and chimpanzees walk on their knuckles, the Turkish siblings put their weight on the wrists, lifting their fingers off the ground.