Isotopic evidence for the timing of the dietary shift toward C ₄ foods in eastern African Paranthropus

Significance Reconstructing the dietary adaptations of our earliest ancestors is critical to understanding the evolution of our relationship with our environment. Here, we present carbon isotope data from hominins of the Shungura and Usno Formations, both part of the Pliocene to Pleistocene Omo Group, Ethiopia, a key sequence for the study of hominin evolution in eastern Africa. Our data show that about 2.37 Ma the diet of both robust and gracile hominins shifted profoundly toward consumption of C 4 -derived foods (largely grasses and sedges), within the temporal range of an early member of the genus Paranthropus aethiopicus . This dietary shift in both groups of hominins occurred during a period marked by similar patterns for coeval herbivore taxa.