ABSTRACT
Understanding the growth of craniofacial systems in mammals, particularly in man, has always posed problems. Such craniofacial systems are formed ontogenetically of multiple tissue types, and the contributions of these tissues do not obviously match the divisions of adult skeletal elements (see Thorogood, this volume). Even the kind and number of segments in the head region continue to attract attention (Maderson, 1987). Furthermore, craniofacial systems appear to show trends toward an unusual number of developmental abnormalities or teratologies. Many of these teratologies suggest that we are not looking at a simple coordinated whole (Salinas, 1982; Shprintzen, 1982); rather, it seems as if multiple cranial and facial components incur differential growth either symmetrically or asymmetrically.
It seems instructive to treat the basis of this curious array of complications from an evolutionary viewpoint, considering two aspects, adaptation and history.
