The Ulas family live in rural southern Turkey. In total, 19 children live with their parents, seven of whom are intellectually disabled and the rest non-disabled. Subject to intense research, the family has five children who display extreme imbalance along with their cognitive disabilities, which make it difficult for them to stay upright while walking. As a result, these five children all move around on their hands and feet, having become adept at moving in this way after years of never standing upright.

When observed by Üner Tan of Çukurova University Medical School in Adana, Turkey, it was concluded that the way some members of the Ulas family moved closely resembled how ancient Homo sapiens would have walked before evolution made them become bipedal, and it was controversially claimed they were a result of “backwards evolution”. In doing so, their condition was dubbed Üner Tan syndrome.

However, a BBC documentary looked to take a more biological and sympathetic approach towards the family. Spurred on by an unpublished paper by Üner Tan explaining his observations and ideas, British scientists Nicholas Humphrey and John Skoyles joined Tan on a visit to the Ulas family alongside a film crew, where they documented every step of the journey.