External environmental variation during gestation impacts the physiology of human development in utero, affecting birth weight, disease risk, and longevity, but evidence for these impacts has not yet been explored in dentition. We examined the relationship between variation in gestational environmental temperature and fluctuating asymmetry (FA) in deciduous dentition. FA measures developmental instability by quantifying random deviation in body structures. Because deciduous teeth form during prenatal life, dental FA captures signals of stress during gestation. We measured dental casts representing 172 child participants (ages 3-6 years) with health history records from the longitudinal Burlington Growth Study. FA was calculated from crown dimensions and inter-cusp distances that develop during gestation. Temperature information was sourced from historical weather statistics based on the nine months preceding each participant’s birth date, binned into trimesters. The sample was divided by sex (n_female=81) to examine if males and females respond differently to temperature stress. Using multiple regression, we tested for the effects of average temperatures in each trimester, controlled for year of birth. Regression results indicate that, in females, an increase in average temperatures during the first trimester is significantly associated with an increase in FA (β=0.027, p=0.03) when controlling for year of birth. There is no relationship in the second or third trimesters in either sex, during which enamel is laid down. Our results suggest the first trimester may set the trajectory for dental developmental instability. Additionally, there may be sexual dimorphism in the response of dental development to temperature stress.

Funding was provided by the Wenner-Gren Foundation: Dissertation Fieldwork Grant; and University of New Mexico: New Mexico Research Grant, Joseph Powell Anthropology Endowment Award, Anthropology Research Development Award.