Thursday, February 23, 2006
Discovered genetic defect creates devo-lution into ape-like people
An editor of a noted scientific journal says he has discovered a genetic defect that seems to set back the clock on human evolution by more than a million years.
Its victims walk on all fours and mouth a primitive language, the scientist reported. He added that the syndrome may literally undo eons of evolution, and thus reflect with some accuracy what our ape-like ancestors were like.
The researcher, Uner Tan of Cukurova University Medical School in Adana, Turkey, has posted an online video clip of an affected woman walking on all fours, her face blurred.
The idea that evolution can run backward isn’t new; some scientists say there have been confirmed cases of it in animals. But it’s also a controversial subject, and considered hard to prove in any given case.
Tan, at any rate, argued that this could be a case of it, so the mutation—known to run in one Turkish family—might offer scientists an unprecedented glimpse into human origins.
“This syndrome interestingly exhibits prehuman features” and represents “possible backward evolution,” he wrote in a paper describing the condition. As such, it “can be considered a live model for human evolution.”
The paper appears in the March issue of the International Journal of Neuroscience, where Tan sits on the editorial board. He also named the condition after himself: Unertan syndrome.
The mutation could shed light on the “transition from quadrupedality to bipedality”—from four-legged to two-legged walking, he wrote. Possibly more important, he added, it may illuminate the evolution of the mind.
“The children exhibiting this syndrome originated from a family having 19 children,” he wrote in another recent paper, in the journal Neuroquantology. Five of these, aged 14 to 32 years, “walked on two palms and two feet, with extended legs… They could stand up, but only for a short time, with flexed knees and heads.”
“The patients had a rather primitive language... they spoke to each other using their own language, using only a few hundred words” which the parents could partly understand, Tan wrote.
“They were mentally retarded; they could not count from one to ten. They were not aware of time and space. For instance, they did not know where they live (which country, which village, which city). They were unaware of year, season, day, and time. Otherwise, they had quite strong legs and arms.”
“The sitting posture was rather similar to an ape,” Tan added. “They could not hold their heads upright; the heads were flexed forward with their skulls. They could not raise their heads to look forward. This head posture with flexed skull was rather similar to the head posture of our closest relatives, like chimpanzees.”
Like most primates, Tan observed, victims of the syndrome walk with a characteristic sequence of movements: after a foot touches the ground, the hand on the other side does. “They could walk fairly fast using their strong legs, without any imbalances.”
Tan said in an email that with colleagues, he has mapped the defect to a region of the genome called chromosome 17p, a site of some of the biggest genetic differences between humans and chimps. Other researchers have also recently linked bipedalism to 17p.
Tan’s report is reminiscent of a 2002 discovery that a different mutation, affecting a gene called FoxP2, created severe speech and grammar problems.
That finding has sparked intense research into what scientists think could be the first known “language gene.” FoxP2-mutated patients also have some coordination difficulties, prompting much discussion among scientists of possible links between language and coordination.
Those patients aren’t reported to have problems standing up, though, unlike those Tan studied.
Scientists generally consider the transition to upright walking as the most important event in human evolution, according to Tan. This freed the hands for skilled movements such as throwing and toolmaking, he added, and may have even made consciousness possible—though a growing number of scientists say consciousness might not be unique to humans.
Video clip here.
Posted by C. at 11:24 AM