Emily Moes^1,2, Heather JH Edgar^1,3

¹Department of Anthropology, University of New Mexico, Albuquerque, NM

²Department of Physician Assistant Studies, University of St. Francis, Albuquerque, NM

³Office of the Medical Investigator, University of New Mexico, Albuquerque, NM

ABSTRACT

Objectives: Research working to reconstruct patterns of health in the recent and deep past often use  fluctuating asymmetry (FA) in the dentition to measure developmental instability during specific ages of development, but the link between FA and environmental stressors is unclear, possibly due to methodological and sex-specific differences. We investigate FA in the permanent dentition together with sociocultural and environmental factors hypothesized to influence early-life health.

Materials and Methods: We collected data from dental casts and health history records from the longitudinal Burlington Growth Study, representing 303 participants. Six indices of FA were created to test for variation in the relationship between environmental factors and ages of susceptibility to dental plasticity. These indices were separated by the ages at which traits are developing, as well as types of measurements used. Using linear regression and separating by sex, each index was systematically examined with the co-occurring or preceding parental and childhood factors.

Results: Of the 34 variables examined, we found that each index is associated with only 1-4 variables, if any, which account for very little variation in FA (adj. R² = 0.02-0.06). Dental FA in males was associated with a history of illness prior to age 1, mother’s height, mean temperature during the fourth and fifth prenatal months, parental group membership, and father’s education. Dental FA in females was associated with mother’s age at parturition, deciduous dental FA, mother’s prior history of miscarriage, breastfeeding history, and father’s education.

Discussion: For both males and females, acute and chronic stresses were associated with increases in dental FA, although rarely were the stresses the same between sexes, possibly due to dimorphism in growth investment strategies. The body’s sensitive windows of development and inherent trait differences in susceptibilities to disruption are responsible for variation in dental FA. Dental FA may be a better reflection of early life stress when used in combination with other biomarkers.