The origin of the Homo sapiens lineage: When and where?

Abstract

It is often assumed that both our species and the last common ancestor (LCA) of Neanderthals and modern humans originated in Africa, with all Eurasian Pleistocene populations expected to ultimately come from Africa. This paper aims to review the Middle Pleistocene fossil record of Africa and Southwest Asia to reinforce the need to at least consider the possibility of a non-African origin for the “sapiens lineage” as a plausible hypothesis. While the fossil record from the late Middle Pleistocene of Africa does suggest that the earliest representatives of Homo sapiens are indeed found in this continent, we found no consistent evidence showing that the LCA necessarily also originated in Africa. At present, based on paleogenetic analyses, the most widely accepted hypothesis suggests that the LCA may have lived during the early Middle Pleistocene. To this information, we must add the constellation of traits observed in H. antecessor, a species that from both morphology and molecular data has been interpreted as being close to the LCA. The morphology of the LCA may be defined by a mosaic of features in the cranium and dentition which, so far, has not been found in the African record. We emphasize that the case for an African origin for the LCA is not a closed one. We suggest caution and the need for further findings and studies, especially in Southwest Asia, which may be a critical region for studying the divergence of H. sapiens and H. neanderthalensis.