Homeotic Evolution in the Mammalia: Diversification of Therian Axial Seriation and the Morphogenetic Basis of Human Origins
(A) Humans appear to retain the original hominiform longer flexible lumbar region. (B) Anatomical reconfiguration results in effective elimination of the lumbar region in Gorilla. (C) Despite a modal number of 5 lumbars, humans may have 4 lumbar but maintain a long flexible lumbar region. (D) Molecular phylogeny suggests that lumbar region shortening in Pan occurred independently and convergently (X-ray in D after Filler 1979 ).