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Efforts to date the oldest modern human fossils in eastern Africa, from Omo-Kibish^{, –} and Herto^, in Ethiopia, have drawn on a variety of chronometric evidence, including ⁴⁰Ar/³⁹Ar ages of stratigraphically associated tuffs. The ages that are generally reported for these fossils are around 197 thousand years (kyr) for the Kibish Omo I^,,, and around 160–155 kyr for the Herto hominins^,. However, the stratigraphic relationships and tephra correlations that underpin these estimates have been challenged^,. Here we report geochemical analyses that link the Kamoya’s Hominid Site (KHS) Tuff, which conclusively overlies the member of the Omo-Kibish Formation that contains Omo I, with a major explosive eruption of Shala volcano in the Main Ethiopian Rift. By dating the proximal deposits of this eruption, we obtain a new minimum age for the Omo fossils of 233 ± 22 kyr. Contrary to previous arguments^,, we also show …