Turkish Family Walks On All Fours Like Animals
Scientists Go Ape As Family Walks On All Fours
By Sam Lister in London 08-03-2006 FIVE brothers and sisters who can walk naturally only on all fours are being hailed as a unique insight into human evolution after being found in a remote corner of rural Turkey.
Scientists believe the family may provide information on how man evolved from a four-legged hominid to develop the ability to walk on two feet more than three million years ago.A genetic abnormality that may prevent the siblings, aged from 18 to 34, from walking upright, has been identified.
The discovery of the Kurdish family in southern Turkey last July has triggered a fierce debate.
Two daughters and a son have only ever walked on two palms and two feet, with their legs extended, while another daughter and son occasionally manage a form of two-footed walking.
The five can stand up, but only for a short time, with both knees and head flexed.
Some researchers claim that genetic faults have caused the siblings to regress in a form of "backward evolution".
Other scientists argue more strongly that their genes have triggered brain damage that has allowed them to develop the unique form of movement.
But all agree that the family's walk, described as a "bear crawl", may offer invaluable information on how our apelike ancestors moved.
Rather than walking on their knuckles like gorillas and chimpanzees, the family are "wrist walkers", using their palms like heels with their fingers angled up from the ground.
Scientists believe this may be the way hominids moved, allowing them to protect their fingers for the more delicate and dextrous manoeuvres so critical in the evolution of man.
Nicholas Humphrey, evolutionary psychologist at the London School of Economics, who has visited the family, said the siblings appeared to have reverted to an instinctive form of behaviour encoded deep in the brain, but abandoned in the course of evolution.
"It has produced an extraordinary window on our past," he said. "It is physically possible, which no one would have guessed from the (modern) human skeleton."
Professor Humphrey, who has been contributing to a BBC program, The Family that Walks on All Fours, to be broadcast on March 17, said that weeks of study, and factors such as the shape of their hands and the callouses on them, showed this was a long-term pattern of behaviour and not a hoax.
The siblings, who live with their parents and 13 other brothers and sisters, are mentally retarded as a result of a form of cerebellar ataxia - an underdevelopment of the brain similar to that in cystic fibrosis.
Their mother and father, who are themselves closely related, are believed to have passed down a unique combination of genes resulting in the behaviour.
Professor Humphrey said cultural influences in their upbringing might have played a crucial role, with parental tolerance allowing the children to keep to quadrupedal walking.
But others believe the cause is more purely genetic.
Uner Tan, a professor of physiology at Cukurova University in Adana, Turkey, who first brought the family to the attention of scientists, argues that the gene mutations have made them regress to a "missing link" primate state.
Researchers said that while the women affected - Safiye, 34, Senem, 22, and Amosh, 18 - tended to spend their time sitting outside the family's very basic rural home, one brother, Huseyin, 28, went into the local village on all fours, where he could engage in the most basic interactions.
Jemima Harrison, of Passionate Productions, which produced the documentary, said the family's identity and location were not being disclosed.
"They walk like animals and that's very disturbing at first," she said. "But we were also very moved by this family's tremendous warmth and humanity."
Story from The Times.
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.
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.
Tool use
"What's significant about that is that chimpanzees ruin their fingers walking like that," Professor Humphrey, an evolutionary psychologist, told the BBC News website.
He added that calluses pictured on the hands of one family member demonstrated that the behaviour was not a hoax.
Professor Humphrey said this could be the way that humankind's direct ancestors walked.
Hands which have kept the fingers dextrous would also have been able to manipulate tools, a key development which influenced the evolution of the human body and intelligence.
"I think it's possible that what we are seeing in this family is something that does correspond to a time when we didn't walk like chimpanzees but was an important step between coming down from the trees and becoming fully bipedal," the LSE researcher said.
'Infant walking'
Professor Humphrey thinks that the brain abnormality simply caused the siblings to rediscover a form of locomotion used by our ancestors.
"Because of the peculiar circumstances they were in, they kept walking as infants," he said.
But a team led by Stefan Mundlos of the Max Planck Institute in Berlin, Germany, thinks that the genetic abnormality which causes the children's unusual gait may have played a more fundamental role in evolution.
Professor Mundlos has located the gene on chromosome 17 and speculates that a gene important in the transition to bipedalism may have been knocked out in the children.
Producer on the documentary Jemima Harrison said the programme's producers were moved by the family's "tremendous warmth and humanity".
BBC Two's The Family That Walks On All Fours is broadcast on Friday 17 March at 2100 GMT
http://news.bbc.co.uk/go/pr/fr/-/1/hi/sci/tech/4782492.stm
