Rapid early Pleistocene climate, vegetation, and fire dynamics in the Turkana Basin

Rapid climate and ecosystem dynamics have been shown to affect evolutionary changes in hominins, including the development of stone tool technology. However, multi-proxy reconstructions of environment changes at timescales that can resolve these transitions, which are crucial for testing hypotheses on the nature of this relationship, have been limited. Further, the interplay between various environmental parameters, namely precipitation, vegetation, and fire, may have nonlinear or otherwise complex interactions that are important for our understanding of evolutionary responses. Here, we present new millennially resolved leaf wax hydrogen and carbon isotope, polycyclic aromatic hydrocarbon (PAH), and pentacyclic triterpene methyl ether (PTME) biomarker datasets from the HSPDP-WTK13 sediment core extracted from the Turkana Basin in Kenya. The drill site is proximal to multiple Acheulean archaeological and hominin discovery sites. Our West Turkana records span a single high-amplitude insolation cycle (∼21 kyr) just after 1.76 Ma, coinciding with the earliest evidence for Acheulean technology from the nearby Kokiselei site complex. In the context of nonlinearly increasing precipitation strength as a response to insolation, we find a parallel increase in fire activity, which indicates a fuel-limited, rather than moisture-limited, fire regime. While the relationship between climate and vegetation appears to be more complex, there is coherence between ecosystem parameters on the millennial scale whereby fire acts as an ecological disturbance, dampening vegetation growth in the context of strong rainfall while allowing for significantly stronger fire activity during times of mixed C 3 -C 4 ecosystems. Abrupt transitions in climate and vegetation structure likely had a large effect on hominins by exerting selection pressures favoring greater behavioral plasticity and constraining the conditions that promoted natural fires that may have been manipulated by hominins. With high-resolution, multi-proxy biomarker data, we are better able to deconvolve climate-ecosystem relationships and their impact on our hominin ancestors.