tags: The Mystery of the Family That Walks on All Fours, Nova, PBS, television, disability, birth defect, heritable mutation, inbreeding, genetics, molecular biology, neurobiology, developmental biology, streaming video
This fascinating video is a complete episode of the American science program, Nova. This episode is about a Turkish family where all the children -- who are adults -- walk on all fours. This episode, which started out as an exploration of the neurobiology and genetics behind this curious behavior turned into a touching human story about a family trying to deal with a devastating disability.
Link: 
An older example.
"A Fact- There are at present two children at Curwyt in Devonshire, who have been suffered, by their mother, to run wild from infancy rather than accept parish assistance. The one is a boy of ten, the other a girl of twelve years of age. They are both in a state of nature, feeding only on wild berries, and running on all fours with amazing celerity. If pursued, they utter a terrific scream, and hide themselves on the top of a hill, or in the recesses of a thicket. They are never seen in a standing posture; nor can they be prevailed on to approach any person but their mother, with whom, though they cannot speak, they have always kept up a distant and fearful communication.” “What is become of these children, or whither they be yet existing, I cannot tell, though I have ordered an inquiry to be made.”
Lord Monboddo citing from a local newspaper article, Antient Metaphysics, volume 4. 1779