Abstract Previous study of the strontium calcium ratio (Sr/Ca) of robust australopithecine skeletons from the Transvaal site of Swartkrans indicated that this Pleistocene hominid was an omnivore, suggesting that models for niche differentiation amongst contemporaneous hominids based on trophic level (i.e. Homo sp. = omnivore vs. A. robustus = herbivore) may be incorrect. In this study, we report that relatively elevated Sr/Ca is found in Homo sp. when compared to Australopithecus robustus skeletons from Swartkrans (ca. 1·8 ma BP). Examination of 87 Sr/ 86Sr in the same skeletons reduces the possibility that the result is due to different substrate sources of Sr. Foods with elevated Sr/Ca in the general area of Swartkrans are mainly geophytes, suggesting that the early Homo niche may have included relatively intensive exploitation of underground plant resources.