Homo naledi and Pleistocene hominin evolution in subequatorial Africa

Abstract

New discoveries and dating of fossil remains from the Rising Star cave system, Cradle of Humankind, South Africa, have strong implications for our understanding of Pleistocene human evolution in Africa. Direct dating of Homo naledi fossils from the Dinaledi Chamber (Berger et al., 2015) shows that they were deposited between about 236 ka and 335 ka (Dirks et al., 2017), placing H. naledi in the later Middle Pleistocene. Hawks and colleagues (Hawks et al., 2017) report the discovery of a second chamber within the Rising Star system (Dirks et al., 2015) that contains H. naledi remains. Previously, only large-brained modern humans or their close relatives had been demonstrated to exist at this late time in Africa, but the fossil evidence for any hominins in subequatorial Africa was very sparse. It is now evident that a diversity of hominin lineages existed in this region, with some divergent lineages contributing DNA to living humans and at least H. naledi representing a survivor from the earliest stages of diversification within Homo. The existence of a diverse array of hominins in subequatorial comports with our present knowledge of diversity across other savanna-adapted species, as well as with palaeoclimate and paleoenvironmental data. H. naledi casts the fossil and archaeological records into a new light, as we cannot exclude that this lineage was responsible for the production of Acheulean or Middle Stone Age tool industries.

Keywords: Dinaledi Chamber; Homo naledi; Lesedi Chamber; evolutionary biology; genomics; hominin; human evolution; none; paleoanthropology.

Figure 1.. African fossil sites from the Middle and earliest Late Pleistocene.

Sites discussed in the text are highlighted in pink here. Geological age estimations for each fossil hominin assemblage are given in Table 1, along with references. DOI: http://dx.doi.org/10.7554/eLife.24234.003

Figure 2.. Phylogenetic scenarios for H. naledi.

A simplified cladogram of Homo, with the possible placements of H. naledi indicated. The cladogram places A. africanus as an outgroup to the Homo + Au. sediba clade, as consistent with nearly all phylogenetic analyses of these species (Berger et al., 2010; Dembo et al., 2015, 2016). To simplify the tree, we have omitted H. antecessor, H. heidelbergensis and Neanderthals, which all phylogenetic analyses place as sisters to H. sapiens relative to H. erectus. There is no present consensus about the branching order among H. habilis, H. rudolfensis, H. floresiensis and Au. sediba (Dembo et al., 2015, 2016), and so these are depicted as a polytomy. DOI: http://dx.doi.org/10.7554/eLife.24234.005