
For 17 years, the scientific community has been trying to shed light on the mystery of five members of the Ulas family in southeastern Turkey who walk on all fours.
The Kurdish family lives in isolation in a remote corner of Turkey. However, some of its members seem to have put a "shield" on three million years of human evolution.
Of the 19 children born to Rezi and Hatis, who walk like any ordinary person, five members walk on four legs, so the hands also perform the functions of the legs.
Some scientists have described their condition as "regressive", but this theory has drawn criticism from other experts who argue that it is a combination of "genetic" factors.
Others argue that an important factor in their condition depends on the conditions and environment. Their skeleton is more ape-like than human.
Although they did not go to school, they managed to learn the Kurdish language to communicate with other family members. For more than 20 years, the family's existence remained hidden, until two British scientists came across an unpublished paper by a Turkish professor in 2005.