Frost et al. (1) show that molars of the East African Theropithecus oswaldi lineage become systematically larger from 4.0 to 0.5 My. They use this trend to infer ages for various South African fossil sites, assuming no clinal variation in tooth size over the continent. They estimate an age of ca. 2.4 My from the large T. oswaldi darti teeth at Makapansgat. Sterkfontein Members 4 and 2 lack Theropithecus but preserve other cercopithecid species similar to Makapansgat, so they propose a similar age, rejecting radiometric dates and stratigraphic observations (2) placing Sterkfontein Members 4 and 2 from ca. 3.4 to 3.7 My. We do not question that tooth size can be helpful for relative dating in East Africa but rather challenge the extrapolation of inferred ages to Sterkfontein. Frost et al. have based their age estimate for Sterkfontein mainly on paleomagnetism and U-Pb dating of flowstones and the presence of Cercopithecoides williamsi, "true" Papio, and Parapapio, which they compare with Makapansgat.