Meagan Vakiener Flint

Preliminary abstract: Mammalian mothers experience tradeoffs during the weaning process: increase lactation duration or caloric content of breast milk to reduce the risk of infant mortality, or terminate offspring nutritional dependence to invest in future reproduction. Modern humans show variation in weaning age, but have an accelerated schedule compared to our closest living relatives, the great apes. A comparatively early weaning age may be related to higher quality nutrition, changes in food preparation such as cooking, or increased alloparental care, but the evolutionary origin of accelerated weaning in humans is poorly understood due to difficulties investigating weaning in the fossil record. The microanatomy of teeth preserves an incremental record of their growth, visible as daily and near-weekly layers that are relatively immune to chemical alterations. Since trace elements are incorporated into dental tissues in proportion to their dietary intake, their microspatial distribution within the normal sequence of growth increments can be used to reconstruct dietary history during tooth development. This proposed research seeks to validate using the distribution of calcium-normalized strontium and barium intensities in dental tissues to reconstruct the timing of weaning transitions, and to investigate weaning age variability within a single well-documented wild population of Virunga mountain gorillas (Gorilla beringei beringei) in Rwanda. The ability to partner behavioral and chemical tooth data from individuals in this population represents a unique opportunity to test an emerging methodology for recovering direct evidence of weaning in the human fossil record and for testing other weaning proxies used for skeletal remains and living populations.