Five members of a Kurdish family in Turkey, who can only walk naturally on all fours, are being hailed as a unique insight into human evolution.
Scientists told the Times of London the family might provide invaluable information on how humans evolved from four-legged hominids, developing the ability to walk on two feet more than 3 million years ago.
Two daughters and a son have only walked using two palms and two feet, with their extended legs, while another daughter and son occasionally manage a form of two-footed walking, the Times reported, noting all five can stand upright, but only for a short time.
Last year's discovery of the family in rural southern Turkey has produced a scientific debate: Some researchers believe genetic faults caused the siblings to regress in a form of "backward evolution," while other scientists claim genes triggered brain damage.
But Nicholas Humphrey, a London School of Economics evolutionary psychologist, told the Times weeks of study indicate their method of walking is a long-term pattern of behavior and not a hoax.
"However they arrived at this point, we have adult human beings walking like ancestors several million years ago," Humphrey said.
Copyright 2006 by United Press International
Explore further: New study uncovers factors in students' reporting of weapons at school