Razib has chimed in on the latest piece of research to come from John Lukacs, “Fertility and Agriculture Accentuate Sex Differences in Dental Caries Rates,” published in Current Anthropology. Throughout time, women have had more cavities on average than men. I’ve explained how cavities are formed in a previous post. Diet change and sexual division of labor have been suggested to be the dominant forces at play. With the Neolithic revolution, the human diet and lifestyle was dramatically revamped. With steady food sources, people reproduced faster and populations boomed.
Lukacs did a comprehensive review of records of the frequencies of dental cavities in both prehistoric and living human populations in his paper. His sample included teeth from people of Euro-American ancestry, and from Africa, teeth from Guinea-Bissau, Madagascar, and Niger… from Asia, he covered China and Taiwanese aboriginals.
He concluded that the increased sedentary lifestyle and fertility increased the demands on the female reproductive system, which in turn intensified the negative impacts of dietary change on oral health. of women He attributes the increased rates of dental caries in females to three factors:
- Female sex hormones, like estrogen, significantly impact cavity formation. Estrogen is produced by the placenta throughout a pregnancy and the levels increase steadily until birth.
- Females produce less saliva than men. Saliva has two important components, enzymes like amylase, that begin break down of complex sugars. If these sugars aren’t broken down, microbes in the mouth consume them and as a biproduct release acids that break down the enamel of the tooth. Saliva also has another component, antibodies and phagocytes that attack the very microbes that cause cavities.
- Women crave high-energy, sweet foods during the third trimester which we all know are promotes cavities and dental decay.
So ultimately female physiology combined with the the changes in diet and increased feritlity are the reasons why women have more cavities than men. Razib mentions that with increased fertility comes a reciprocal increase infant mortality, especially because the agricultural revolution increased communicable diseases. He concludes that hunter-gatherer infants are far more likely to reach reproductive age than infants of an agriculturalist.
But I disagree. Despite the recent popularity of the paleo-diet, the real hunter gatherer lifestyle is not easy. Many hunter gatherer societies have erratic sources of nutrition, very few have regular caloric intakes. John Hawks explained that among hunter gatherers, like the Hiwi, only 43% of the adults were expected to see the age of 30. Furthermore, many hunter gatherer cultures also have food taboos which dictate the diets of females. For example, Australian aboriginal societies restrict protein and fat foods for pregnant and lactating women. Similar traditions exist in Africa too. In Athapaskan societies, females at menarche cannot eat fresh meat.
Women who do not consume many calories, reach menarche at an older age and become amenorrheic — irregularly menstruate. If and when they do have a child, they are often of low birth weight, and the child has a higher risk of dying because they have little to no fat reserves. They consume inadequate amounts of nutrition since the mothers cannot make insufficient amounts of milk. All of which influences birth spacing significantly.
Despite the increased probability of cavities, the Neolithic revolution has generally been a good thing for women and children.
- John R. Lukacs (2008). Fertility and Agriculture Accentuate Sex Differences in Dental Caries Rates Current Anthropology, 49 (5), 901-914 DOI: 10.1086/592111