The hominin fossil record of the Omo-Turkana Basin

The Omo-Turkana Basin is one of three major regions for the study of hominin evolution in Africa. It has yielded a rich hominin fossil record of 1231 specimens, around a third of the record for the whole of Africa for the period from the Messinian through the Calabrian. Here, we consider the fossil hominin record of the Omo-Turkana Basin as an object of study in its own right and show the contribution that an analysis of such an exhaustive record can make. The data come from 117 publications allowing the most complete, accurate, and up-to-date synthesis of this record. Our analysis provides a quantitative perspective on the biases affecting this record, such as skeletal element abundance representation, chronostratigraphic distribution, and difficulties in taxonomic assignment. It also provides historical perspective, illustrating the major contribution made by the Omo-Turkana hominin fossil record to our knowledge of human evolution. We provide a synthetic overview of the taxa represented and discuss the chronological distribution of taxonomic groups in the basin including the relative abundance of Paranthropus and Homo (2/3 and 1/3, respectively) during their long period of coexistence. Integrating the data makes it possible to address difficult questions that have been underinvestigated until now. For example, contrary to the prevailing view, the genus Homo is well represented in the Omo-Turkana Basin between 2.7 and 2 Ma. Additionally, we show that the hominin fossil record of the Upper Burgi and KBS Members is atypical, both in terms of skeletal element abundance and taxonomy. Neither paleoenvironments nor taphonomic or collecting biases can fully explain this anomaly.