The members of the family use the palms of their hands in a "bear crawl".
A family living in Turkey has baffled scientists studying the evolution of humans. Certain members of the Ulas family walk on all fours, which had not been observed in fully-grown adults before this discovery. This unusual behaviour was first documented in a 2006 BBC documentary titled 'The Family That Walks on All Fours'. The video shows the members of the family using the palms of their hands in a "bear crawl". A scientific paper has also been published, giving details about the family.
The BBC quoted Professor Humphrey, from the London School of Economics (LSE), as saying that four sisters and one brothers were born with the unusual trait that could yield clues to why our ancestors made the transition from four-legged to two-legged animals.
Unfortunately, a sixth member of the family, who also had the characteristic, died.
"I never expected that even under the most extraordinary scientific fantasy that modern human beings could return to an animal state," Professor Humphrey said on 60 Minutes Australia.
"The thing which marks us off from the rest of the animal world is the fact that we're the species which walks on two legs and holds our heads high in the air," he explained.
"Of course, it's language and all other sorts of things too, but it's terribly important to our sense of ourselves as being different from others in the animal kingdom. These people cross that boundary," added the expert.
A study by researchers at Liverpool University said that the children at the centre of the study had skeletons with more resemblance to apes than humans and a shrunken cerebellum, said New York Post.
Professor Humphrey later said that a physiotherapist later and equipment used to help them walk on just two feet, which led to significant improvements in mobility.