Holocene vegetation dynamics of the Koobi Fora Basin, East Turkana, Kenya: Insights from phytolith analysis

The Koobi Fora Basin is renowned for its rich paleontological and archaeological record. Despite extensive study of earlier periods the Holocene (∼11,7000 years ago to present) sedimentary record, the Galana Boi Formation, remains understudied. This Formation preserves a record of lake-level fluctuation, environmental shifts, and the appearance of the first herders in eastern Africa around ∼5000 years ago. Here we examine Holocene vegetation change using phytolith and chronological data from five archaeological sites. Phytoliths from twenty Holocene, and three modern samples from Ileret, Karari and Koobi Fora were extracted using heavy liquid flotation. All phytoliths encountered were identified and classified. Our data show subtle temporal changes in vegetation cover from wooded grasslands in the early Holocene to open wooded grasslands in the mid Holocene. By late Holocene, the; vegetation cover had transitioned to open grassy shrublands. Broadly, the phytolith; assemblages likely reflect local to regional scale vegetation. However, at Karari ridge, intra-site differences suggest localized, small-scale anthropogenic modification, indicated by; elevated abundances of useful taxa, such as palms. The phytolith data suggest that climate became progressively drier from 6000 years ago to present, consistent with basin-wide paleoenvironmental reconstruction from leaf wax biomarkers. These ecological changes coincided with shifts in socio-economic subsistence strategies. Early Holocene populations engaged in hunting, gathering, and fishing while the mid Holocene, early pastoralists appear within the basin, but continued to use diverse wild food resources alongside maintaining livestock (caprines and cattle). The reduced woody cover density, together with decline in wetland indicators over the past four millennia, gradually transformed the region into sparsely; vegetated landscapes observed today. These changes subsequently shaped and sustained; resilient pastoralist lifeways under increasingly arid conditions. An increased sample size and multiproxy approach are crucial for understanding Holocene spatiotemporal human-environment interactions in the Basin and for understanding human resilience to environmental pressures, including unpredictable climate change and contemporary lake-level fluctuations Lake Turkana.