Contextualising early hominin environments: A multi-proxy palaeoenvironmental reconstruction of the earliest Oldowan at Nyayanga, western Kenya

Several early Oldowan localities are known from the Homa Peninsula, in southwestern Kenya, the oldest of which, Nyayanga (∼3–2.6 Ma), preserves the earliest known evidence of Oldowan tool assemblages, long-distance raw material transport, and butchery. Here, we present a multi-proxy reconstruction of hominin environments at Nyayanga, using stratigraphy, particle size, phytoliths, and stable isotopes to reconstruct the site's sedimentary dynamics, depositional environment, and palaeovegetation. Four units have been identified from Nyayanga (NY-1 to NY-4); this study concentrates on NY-1 to NY-3. The site is interpreted as a former alluvial plain environment where deposition occurred through episodic hyperconcentrated flows and intermittent unconfined fluvial flows. During flow hiatus, secondary processes, including fluvial runoff and aeolian deposition, occurred, along with the development of a stable land surface. Climatic conditions at Nyayanga are characterized as moderately seasonal and well-watered. Isotopic analyses of fossil mammals and pedogenic carbonates, alongside phytolith taxonomic analyses, demonstrate that C 3 vegetation is underrepresented throughout the sequence, whereas higher abundances of C 4 plants could indicate a dense ground cover. Based on multi-proxy evidence, the landscape at Nyayanga becomes more stable through time, showing less frequent higher-energy, hyperconcentrated flows and less unconfined fluvial activity. Soil development increases and becomes more mature with varying levels of pedogenesis.