However, 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 (i.e. on their feet rather than their knees).
The unusual gait in question was attributed by Nicholas Humphrey, who accompanied the documentary makers, to a unique combination of genetic and developmental factors. The mother recalled that all of her 19 children initially walked on their feet instead of using their knees.