When dental caries rates are reported by sex, females are typically found to exhibit higher prevalence rates than males. This finding is generally true for diverse cultures with different subsistence systems and for a wide range of chronological periods. Exceptions exist, but are not common. In this paper, we present new data for sex differences in dental caries rates among the Guanches (Tenerife, Canary Islands), summarize results of meta-analyses of dental caries prevalence, and emphasize new research that stresses the critical role of female hormones and life-history events in the etiology of dental caries. Among the Guanches, corrected tooth-count caries rates for females (8.8%, 158/1,790) are approximately twice the frequency of caries among males (4.5%, 68/1,498). Higher caries prevalence among females is often explained by one of three factors: 1) earlier eruption of teeth in girls, hence longer exposure of girls' teeth to the cariogenic oral environment, 2) easier access to food supplies by women and frequent snacking during food preparation, and 3) pregnancy. Anthropologists tend to favor explanations involving behavior, including sexual division of labor and women's domestic role in food production. By contrast, the causal pathways through which pregnancy contributes to poorer oral health and higher caries rates are deemphasized or discounted. This paper presents recent research on physiological changes associated with fluctuating hormone levels during individual life histories, and the impact these changes have on the oral health of women. The biochemical composition of saliva and overall saliva flow rate are modified in several important ways by hormonal fluctuations during events such as puberty, menstruation, and pregnancy, making the oral environment significantly more cariogenic for women than for men. These results suggest that hormonal fluctuations can have a dramatic effect on the oral health of women, and constitute an important causal factor in explaining sex differences in caries rates.