The Family That Walks On All Fours is a BBC2 documentary that explored the science and the story of five individuals in the Ulas family in Turkey that walk with a previously unreported quadruped gait. The documentary was created by Passionate Productions and was broadcast on Friday 17 March 2006. The voiceover is Jemima Harrison. A revised version of the documentary that shifts the focus away from the story of the discovery of the family and includes the views of additional scientists was shown on NOVA on 14 November 2006. Debate exists as to the nature and cause of their walking, including controversial speculation in the form of the Uner Tan syndrome that it may be a genetic throwback to pre-bipedal hominid locomotion. Nicholas Humphrey, who accompanied the documentary makers, concluded that it was due to a rare set of genetic and developmental circumstances coming together. First, their mother recalls that initially all of her 19 children started off walking with a bear-crawl. Second, due to an inherited recessive genetic mutation, they have a non-progressive congenital cerebellar ataxia that impairs the balance children normally use to learn to walk bipedally. Not being able to manage the balance needed for bipedal walking, they perfected in its place their initial bear-crawl into an adult quadruped gait.