This study asserts that premastication (the pre-chewing of food for infant feeding) has existed as a cross cultural human universal stemming from the post natal immaturity of infant development and their need to have nutritional supplements to breast milk before they develop the molars necessary to consume an adult diet. Hypotheses are informally tested by sampling 119 cultures from the eHRAf database and looking for frequency of premastication occurrence. About one-third with information on infant feeding mention pre-mastication.

The author tests various hypotheses regarding cross-cultural occurrence of geophagy, the eating of earth. Nearly 500 years of references to geophagy were compiled into the Database on Human Geophagy, which was then used to examine biological justifications for this little-understood behavior.