Molecular and isotopic evidence for milk, meat and plants in prehistoric eastern African herder food systems reveal changing selective contexts for lactase persistence

The development of pastoralism transformed human diets and societies in grasslands world-wide. The long-term success of cattle herding in Africa has been sustained by dynamic food systems, consumption of a broad range of primary and secondary livestock products, and the evolution of lactase persistence, which allows digestion of lactose into adulthood and enables the milk-based, high protein, low-calorie diets characteristic of contemporary pastoralists. Despite the presence of multiple alleles associated with lactase persistence in ancient and present-day eastern African populations, the contexts for selection for LP and the long-term development of pastoralist foodways in this region remain unclear. Pastoral Neolithic (c. 5,000-1,200 BP) faunas indicate that herders relied on cattle, sheep, and goats, and some hunting, but direct information on milk consumption, plant use, and broader culinary patterns is rare. Combined chemical and isotopic analysis of ceramic sherds (n=125) from Pastoral Neolithic archaeological contexts in Kenya and Tanzania, using compound-specific δ13C and Δ13C values of the major fatty acids (FAs), provides the earliest chemical evidence for milk, meat, and plant processing by ancient herding societies in eastern Africa. These data provide the first direct evidence for milk product consumption and reveal a history of reliance on animal products and other nutrients, likely extracted through soups or stews, and plant foods. They document a 5,000-year temporal framework for East African pastoralist cuisines, evidence of milk prepared or served in ceramic vessels, and changing cultural contexts through time for selection for the distinctive eastern African genetic basis for lactase persistence.