Patterns of Neoteny in the relative skull growth in Homo and Pan
Succesive stages of
skull development from infancy
to maturity in chimpanzees (top three) and humans (bottom pair).
of both species have a large craniums and small faces. Relatively more
rapid growth of the jaw in juvenile chimps (above, middle)
gives them skull proportions resembling those of adult humans, in which
the relative proportions are less altered (right). Continued rapid
expansion of the jaw in adult apes
(top right & below right) gives them proportionately larger jaws
The two photographs
of a juvenile and adult male chimpanzee are from a 1926 study by the
German anthropologist Adolf Naef. Of the former, he says,"[It] is the the most human-like picture of
an animal, of any that is known to me."