Humans that Walk on All Fours: Scientists Discover Family Isn't Evolving Backwards (VIDEO)

First Posted: Jul 17, 2014 08:18 AM EDT
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In 2006, a group of humans that walked on all fours was made famous by a BBC documentary. Now, scientists have contradicted claims that this group represents a possible example of backwards evolution.

Five siblings in a family that lives in a remote corner of Turkey walk exclusively on their hands and feet due to their condition, called Uner Tan Syndrome (UTS). Since they were first discovered in 2005, scientists have debated the nature of their disability, and some have speculated that they might represent a backward stage of evolution. Now, researchers have looked at this family a bit more closely.

The researchers analyzed 518 quadrupedal walking strides from several videos of people with various forms of UTS, including footage from the BBC documentary of the five Turkish siblings. Then, the scientists compared these walking strides to previous studies of the walking patterns of healthy adults who were asked to move around a laboratory on all fours.

So what did they find? It turns out that nearly all human subjects walked in lateral sequences, which means that they placed a food down and then a hand on the same side and then moved in the same sequence on the other side. In contrast, apes and other nonhuman primates walk in a diagonal sequence; they put down a foot on one side and then a hand on the other side, continuing the pattern as they move.

"Although it's unusual that humans with UTS habitually walk on four limbs, this form of quadrupedalism resembles that of healthy adults and is thus not all unexpected," said Liza Shapiro, one of the researchers, in a news release. "As we have shown, quadrupedalism in healthy adults or those with a physical disability can be explained using biomechanical principles rather than evolutionary assumptions."

The findings reveal that UTS does not represent an example of backwards evolution. People with this condition do not walk like nonhuman primates. Instead, they walk in the same patterns as regular individuals.

The findings are published in the journal PLOS One.

Want to see the family for yourself? Check out the video below, courtesy of YouTube.

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