Direct dating of human fossils and the ever-changing story of human evolution

This review is a follow up to Grün et al. (2006): Direct Dating of Human Fossils. Since that time there has been progress on the experimental side of the geochronological analyses, which are detailed for uranium-series isotope and ESR dating. Also, many new human fossils, including several new species (e.g., H. naledi, H. luzonensis, and H. longi) have been discovered, named and dated. Direct dating of human fossils has contributed to some major revisions in our understanding of human evolution. For example, the enigmatic Homo floresiensis has been dated to >60 ka instead of ∼18 ka as was originally published. This put an end to the heated debate about how H. floresiensis could have survived the arrival of H. sapiens on Flores for several tens of thousands of years. From Africa, results are presented for Swartkrans, Thomas Quarry, Broken Hill (Kabwe), the Rising Star sites Djebel Irhoud, Florisbad and Omo Kibish. In western Asia, human fossils from Mislya, Tabun, Qafzeh and Al Wusta were analysed and in Europe from Payre, Moula Guercy, Lezetxiki, Apidima, El Sidron and Atapuerca (Sima de los Huesos and Gran Dolina). From Asia and Oceania we discuss the results from Denisova, Penghu, Harbin, Liujiang, Liang Bua, Mata Menge, Callao, Ngandong, Sambungmacan, Wajak, Niah and Tabon, while from Australia WLH50 is added to WLH3. We describe the dating procedures for each site. All published data were re-evaluated. The systematic analysis of the U-series isotopic data led to new insights, particularly with respect to detailed U-diffusion processes (provenance of the uranium, leaching, secondary overprints etc.), which altered the interpretation of the ages for some of the sites. For example, we can show that the minimum age of H. luzonensis is 134 ± 14 ka, covering the transition of MIS6 to MIS 5 (younger dates were the result of secondary U-overprints), and that Apidima 1 and 2 have significantly different isotopic characteristics, refuting claims of initial contemporaneous burials. We discuss the implications of the results for our present understanding of human evolution.