The article below is an analysis (in a non-human primate, the hyrax) that
supports the hypothesis that consumption of cooked foods was a factor in the
reduction of face size in humans during evolution. That is yet another example
of culture (cooking food) driving morphological change.

Journal title:    Journal of Human Evolution
Citatin details:  Volume 46, Issue 6 , June 2004, Pages 655-677

Article title:    Effects of food processing on masticatory strain and
craniofacial growth in a retrognathic face

Article authors:  Daniel E. Lieberman, Gail E. Krovitzb, Franklin W. Yatesa,
Maureen Devlina and Marisa St. Clairec


http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJS-4CG0R52-2&_user=10&_handle=B-WA-A-W-AA-MsSAYZW-UUW-AAUDUWDVVY-AAUVZUYWVY-YBAEZZZWY-AA-U&_fmt=summary&_coverDate=06%2F30%2F2004&_rdoc=2&_orig=browse&_srch=%23toc%236886%232004%23999539993%23504276!&_cdi=6886&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=4cbc7c1f4cd9ac18c4a1f11f0055ff32

Abstract

Changes in the technology of food preparation over the last few thousand years
(especially cooking, softening, and grinding) are hypothesized to have
contributed to smaller facial size in humans because of less growth in response
to strains generated by chewing softer, more processed food. While there is
considerable comparative evidence to support this idea, most experimental tests
of this hypothesis have been on non-human primates or other very prognathic
mammals (rodents, swine) raised on hard versus very soft (nearly liquid) diets.
Here, we examine facial growth and in vivo strains generated in response to
raw/dried foods versus cooked foods in a retrognathic mammal, the rock hyrax
(Procavia capensis). The results indicate that the hyrax cranium resembles the
non-human primate cranium in having a steep gradient of strains from the
occlusal to orbital regions, but differs from most non-anthropoids in being
primarily twisted; the hyrax mandible is bent both vertically and laterally. In
general, higher strains, as much as two-fold at some sites, are generated by
masticating raw versus cooked food. Hyraxes raised on cooked food had
significantly less growth (approximately 10%) in the ventral (inferior) and
posterior portions of the face, where strains are highest, resembling many of
the differences evident between humans raised on highly processed versus less
processed diets. The results support the hypothesis that food processing
techniques have led to decreased facial growth in the mandibular and maxillary
arches in recent human populations.

Tom Billings