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 four limbs.

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. Initially, Turkish scientists spoke of evidence of “regressive evolution”.

Of the 19 children born to Rezi and Hatis, who walk straight, five brothers walk with all four limbs, write the newspapers “Daily Express” and “Daily Mirror”. At first researchers thought it was a throwback to the evolution of standing.

But unlike the primates from which humans evolved, the Ulas brothers don’t use their fist to walk, but their palm like monkeys do. Some scientists have described their condition as “regressive”, prompting criticism from other experts who argue it is a combination of “genetic” factors.

Sisters Safiye, Hacer, Senem and Emine as well as their brother Hüseyin have received disparaging comments from villagers in the southern Turkish province of Xatay (near the border with Syria). The family had a total of six children who walked on all four legs, but one died at the age of five.

Family members may be the missing link between humans and apes, scientists say.

Those who walk on all fours are harassed by the wider environment and therefore, mostly women, prefer to move near their home.

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 For more than 20 years, the family’s existence remained hidden, until two British scientists came across an unpublished paper by a Turkish professor in 2005.