Hunter-Gatherer Foraging Strategies in Tropical Grasslands: Model Building and Testing in the East African Middle and Later Stone Age

Hunter-gatherer adaptations to moist tropical grasslands are not well known from either the ethnographic or the archaeological record. This is unfortunate as grassland adaptations are clearly significant to human biological and behavioral evolution. The most effective strategy for remedying this problem is to develop models for grassland exploitation based on strong understandings of the ecological similarities and differences between cold, temperate, and tropical grasslands. Cold, temperate, and tropical grasslands are similar in that water and raw materials are often scarce and the most abundant large mammals are gregarious and mobile. Tropical grasslands differ from cold and temperate grasslands by having a greater diversity and biomass of edible above-ground plants and plants with underground storage organs, making carbohydrate availability greater and less seasonal. Large mobile mammals and resident large mammals are more diverse and have greater biomass in tropical grasslands. Overall, tropical grasslands are a richer and less seasonally punctuated environment than either cold or temperate grasslands. A comparison of ethnographic data regarding variation in foraging strategies in different cold, temperate, and tropical settings lead to the construction of three models for hunter-gatherer exploitation of tropical grasslands: a Generalized Grassland Model (no specialized tactical hunting - considered the favored model given modern African grassland conditions), a Seasonal Grassland Model (only seasonal use of specialized tactical hunting techniques - considered unlikely for Africa), and a Specialized Grassland Model (regular use of specialized tactical hunting strategies - considered highly unlikely for Africa). A preliminary test of these models shows the Athi-Kapiti Plains Holocene archaeological evidence is most consistent with the Generalized Grassland Model. The Last Glacial Maximum is most consistent with the Seasonal Grassland Model. A single MSA occupation also suggests that specialized tactical hunting strategies were used. These differences in hunting strategies were probably due to the differences in ecological conditions between the Holocene and the Last Glacial Maximum.