When Turkish evolution biologist Uner Tan introduced the civilization to a Turkish family members with part members who could walk just on every fours, in a "bear crawl," he and other scientists speculated this strange gait to be the rebirth of a properties lost throughout human evolution.
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Not so, a new study finds.
The family and also other world with Uner Tan syndrome do not represent "a backward stage in person evolution," together Tan wrote in a 2006 document in the global Journal that Neuroscience, said Liza Shapiro, a professor of anthropology at the college of Texas in ~ Austin. In brand-new research, Shapiro and her colleagues contrasted videos of the family"s gait v the gaits the nonhuman primates, together as primates or gorillas. They found the gait fads did no match. Instead of recreating ape walks, world with Uner Tan are simply adapting to their disorder, Shapiro and also her colleagues reported July 16 in the journal PLOS ONE.
On every fours
Tan first noticed the syndrome that currently bears his surname in a household of 19 life in rural southerly Turkey. Five of the family members members walk making use of their feet and also hands, and additionally have cognitive disabilities. The family was the subject of the 2006 BBC2 documentary, "The household That to walk on every Fours."
Research has because revealed the the disorder is caused by a genetic mutation on chromosome 17, i beg your pardon affects the cerebellum, component of the brain responsible because that movement and balance. From the beginning, Tan"s statements around the evolutionary nature of the impacted family"s walking patterns were controversial. The influenced children never had actually physical treatment or adaptive modern technology such together wheelchairs, making their gait a necessity.
But nobody ever challenged the major claim: that the influenced children walked favor nonhuman primates. Primates the walk on every fours execute so in different way than most other mammals, Shapiro called Live Science. Primates to walk in a diagonal sequence, putting down a hind limb and then the opposite front limb: left foot, right hand, appropriate foot, left hand.
Most other mammals walk in a lateral sequence, through the same-side limbs following each other: left foot, left hand, appropriate foot, right hand. Person babies and adults asked to "bear crawl" on hands and also feet generally walk in a lateral sequence, too, Shapiro said.
Adapting, no devolving
Shapiro said she came to be interested in researching the gait of human being with Uner Tan Syndrome in 2006 after seeing the documentary on the Turkish family.
"It was all about whether or not it was evolutionary reversal, which kind of horrified me," she said. Immediately, though, she can see the the household was not making use of the primate diagonal gait.
Shapiro did not have accessibility to great video that the family"s walking trends until recently, once one of she co-authors told she he had footage native the BBC. From the video, she and her colleagues were able come analyze much more than 500 strides do by the five household members with the disorder.
About 99 percent the the strides were lateral, not diagonal — a blow against the id that the family members members had actually "rediscovered" an genealogical primate way of walking. Instead, they were walking like any type of typical adult would certainly if asked to relocate on hands and also feet.
A lateral gait is handy because that long-limbed pets (such as humans) as soon as walking on every fours, she said, since it helps keep the four from bumping right into one another.
"They"re act what any human walk in that situation where they can"t was standing up," Shapiro said.
Shapiro emphasized that even if the family members had relocated with a diagonal gait, the pattern would not prove anything around human evolution or the beginnings of bipedalism.
"Bipedalism requires a lot of changes, physical and anatomical alters in the body," she said. "Neurological changes. Engine changes. It"s not simply one thing."
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Stephanie Pappas is a contributing writer for Live Science. She consist of the people of human and also animal behavior, and also paleontology and other scientific research topics. Stephanie has actually a Bachelor of art in psychology indigenous the college of southern Carolina and also a graduate certificate in science interaction from the university of California, Santa Cruz. She has actually ducked under a glacier in Switzerland and also poked hot lava with a rod in Hawaii. Stephanie hails from eastern Tennessee, the worldwide center because that salamander diversity. Follow Stephanie ~ above Google+.