Open savannah grasslands (dominated by C4 plants) became a significant component of northeast African vegetation during the late Neogene. We present molecule-specific carbon isotopic measurements of terrestrial plant biomarkers preserved in marine sediments off northeast Africa that allow reconstruction of orbital-scale vegetation changes in short time windows over the past 9.4 m.y. The biomarker data show large-amplitude vegetation variability as early as 3.8 Ma, with the greatest C4 expansion occurring after 3.4 Ma. We sampled orbital-scale oscillations of up to 5‰, almost as large as the observed late Neogene range of 7‰, suggesting that large and repeated oscillations between more open and more closed landscapes were an important aspect of northeast African vegetation change during the past 4 m.y.

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