Fine-scaled climate variation in equatorial Africa revealed by modern and fossil primate teeth.

Abstract

Variability in resource availability is hypothesized to be a significant driver of primate adaptation and evolution, but most paleoclimate proxies cannot recover environmental seasonality on the scale of an individual lifespan. Oxygen isotope compositions (δ¹⁸O values) sampled at high spatial resolution in the dentitions of modern African primates (<i>n</i> = 2,352 near weekly measurements from 26 teeth) track concurrent seasonal precipitation, regional climatic patterns, discrete meteorological events, and niche partitioning. We leverage these data to contextualize the first δ¹⁸O values of two 17 Ma <i>Afropithecus turkanensis</i> individuals from Kalodirr, Kenya, from which we infer variably bimodal wet seasons, supported by rainfall reconstructions in a global Earth system model. <i>Afropithecus</i>' δ¹⁸O fluctuations are intermediate in magnitude between those measured at high resolution in baboons (<i>Papio</i> spp.) living across a gradient of aridity and modern forest-dwelling chimpanzees (<i>Pan troglodytes verus</i>). This large-bodied Miocene ape consumed seasonally variable food and water sources enriched in ¹⁸O compared to contemporaneous terrestrial fauna (<i>n</i> = 66 fossil specimens). Reliance on fallback foods during documented dry seasons potentially contributed to novel dental features long considered adaptations to hard-object feeding. Developmentally informed microsampling recovers greater ecological complexity than conventional isotope sampling; the two Miocene apes (<i>n</i> = 248 near weekly measurements) evince as great a range of seasonal δ¹⁸O variation as more time-averaged bulk measurements from 101 eastern African Plio-Pleistocene hominins and 42 papionins spanning 4 million y. These results reveal unprecedented environmental histories in primate teeth and suggest a framework for evaluating climate change and primate paleoecology throughout the Cenozoic.