The relationship between dental age and long bone growth in Arikara infants

The relatively advanced timing of tooth calcification and eruption has been documented in living Native American children. This study uses least squares regression analysis to demonstrate similar precocious patterns of dental development in an archaeological American Indian sample from South Dakota.

Diaphyseal lengths of the femur, tibia, humerus, and radius from Arikara subadults between about birth and three years of age were analyzed using the model, bone length = b₀ + b₁(age) + b₂(age)². Age was estimated using three deciduous teeth and dental calcification standards based on White children. The resulting intercepts were compared to modal perinatal long bone lengths, determined by frequency distributions of the Arikara long bones. If the modal lengths accurately represent mean birth lengths in the Arikara then the intercepts are lower than expected. This discrepancy suggests that the White dental standards are over-aging the Arikara subadults.

By slightly lowering the ages assigned to developmental stages of the second deciduous mandibular molar (DM2), the intercepts were raised so that they approximated the modal perinatal lengths. Regression curves for the deciduous mandibular canine (DC) and the deciduous mandibular first molar (DM1) were then adjusted to fit the adjusted DM2 line. Timing differences among the teeth were noticed. While Arikara DM2 consistently develops relatively early, DC and DM1 are more advanced only until about 0.5 years. A comparison of the adjusted Arikara curves to growth curves for White samples reveals differences in patterns of relative long bone growth and suggests that rates of long bone growth in Arikara infants are advanced relative to the long bone growth rates for White infants.