Saturday, April 5, 2008
Friday, April 4, 2008
After two years in which he sometimes tasted ridicule, there is now some recognition for a Turkish scientist who claims evolution may have gone backward in some unusual countrymen of his. Physiologist Uner Tan’s latest research on the people—who have walked on all fours lifelong—is set to appear in one of the most prestigious scientific journals.
In the research, Tan and colleagues identify a gene linked to the condition, which they call Unertan syndrome.
The publication comes after Tan, facing skepticism and sometimes hostility, had long difficulties in getting his studies on the syndrome published in major journals.
Controversy followed Tan ever since he proposed his reverse-evolution theory, which along with the syndrome itself was first reported to the general public in World Science. The theory—not discussed in the Proceedings paper—holds that the syndome may be a genetic throwback to our ape-like ancestors’ walking style, and thus could shed light on it. Some scientists have called the idea highly implausible. They argue that any mutation causing modern people to walk on all fours must involve a single genetic change, whereas the evolutionary transition to upright walking probably involved many changes.
Others who disagree with Tan have gone further and accused him of sloppy scholarship and even erratic behavior. The scientific debate has been complicated by bitter, more personal disputes between Tan and some colleagues, as well by what some observers have called a circus-like atmosphere that surrounded the syndrome’s discovery in 2006.
Yet amid these controversies, some researchers called Tan’s reverse-evolution hypothesis plausible and testable. Reverse evolution—an organism’s return to genetic characteristics of its ancestors—has been documented to occur in some animals, such as fish that lose their eyes after living in dark caves for generations.
The new paper, co-authored with six of Tan’s colleagues including his wife, Meliha, reports that a responsible mutation has been found in two of four families that by now have turned up affected by “Unertan syndrome.”
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Since the intial report of the syndrome, Tan and colleagues have identified three more Turkish families affected. The Proceedings paper reports that members of two of the families suffer a mutation in a gene called VLDLR, which influences how new brain cells find their way to the right place in the developing brain. One brain region affected is the cerebellum, which governs balance for walking and standing.
In a third family—that of the first discovered cases of the syndrome—Tan’s group confirmed a previous study linking their mutation to a region of a chromosome called 17p. The region is believed to be one of the areas of greatest differences between humans and chimps. Tan has said that this finding supports his reverse-evolution idea. Although the new paper didn’t go into that, he said he expects future studies to look at this issue. Probably “many genes are involved,” he added.