Direct Evidence of Milk Consumption from Ancient Human Dental Calculus

Milk is a major food of global economic importance. Humans have exploited animal milk as a food resource for at least 8500 years, and in order to overcome milk indigestibility during adulthood many populations have developed cultural practices to reduce the lactose content of milk. Additionally, some populations have evolved lactase persistence (LP), a genetic trait that enables continued lactose digestion after infancy. However, the origins, spread, and scale of dairying remain poorly understood. Current lines of evidence, such as lipid isotopic ratios of pottery residues, faunal mortality profiles, and LP allele frequencies, imply a complex history of dairying at the level of populations. However, in order to understand how, where, and when humans consumed milk products, it is necessary to link evidence of consumption directly to individuals and their dairy livestock. Here we report the first direct evidence of milk consumption, the whey protein β-lactoglobulin (BLG), preserved in human dental calculus from the Bronze Age (ca. 5000 BP) to the present day. Using protein tandem mass spectrometry, we demonstrate that BLG is a species-specific biomarker of dairy consumption, and we identify individuals consuming cattle, sheep, and goat milk in the archaeological record. We then apply this method to Greenland's medieval Norse colonies, a population known for its extreme reliance on dairy products. We find a decline of this biomarker in the dental calculus of Norse Greenlanders consistent with diminished access to milk products leading up to the abandonment of the Norse Greenland colonies in the second half of the 15^th century CE.