Human evolution in the Middle Pleistocene: The role of Homo heidelbergensis

For paleoanthropologists working in the Middle Pleistocene, these are interesting times. New discoveries of artifacts and human fossils have been reported from western Europe, so that it now looks as though this continent was populated 800,000 years ago, if not earlier. One of the fossils, from Ceprano in Italy, is described as Homo erectus. Whether this ancient species ever reached Europe has been repeatedly questioned, but the Ceprano cranium is complete enough to provide some hard evidence. Other finds from Spain are even more spectacular. The Sima de los Huesos (‘‘Pit of Bones’’) in the Sierra de Atapuerca has yielded a wealth of skeletons that are best interpreted as early Neanderthals, perhaps close to 300,000 years in age. Older but unfortunately more fragmentary remains, also from Atapuerca, display no Neanderthal features and are claimed as representatives of a new species. Homo antecessor will require close study. These European discoveries focus fresh attention on the evidence accumulating from Africa and Asia. Human bones are known from the earlier Middle Pleistocene of Africa at localities such as Bodo in Ethiopia and Broken Hill in Zambia. The crania show anatomical features that distinguish them from Homo erectus. In the Far East, the people at Dali and other sites are also more advanced than Homo erectus, but their affinities to groups in the West are uncertain. This Middle Pleistocene record, still sparse but increasingly well dated, raises important questions. One concerns the fate of Homo erectus in different regions of the Old World. Another is how many distinct species should be recognized among the descendants of this ancient lineage. It is apparent that the traditional approach of lumping diverse humans together as ‘‘archaic’’ Homo sapiens will no longer work. The picture is highly complex, and several taxa probably are needed to accommodate the fossils. Evolutionary relationships among these populations must be clarified, but pose some major problems. I will address only a subset of these topics pertaining mainly to earlier Middle Pleistocene hominids.