Homo sapiens, Neanderthals and Speciation Complexity in Palaeoanthropology
Tracking the origins of new species and delimiting taxa across space and time present well-trodden sources of controversy for palaeoanthropology. Although biological diversity comes with frustratingly elusive boundaries, the task of describing and understanding diversity remains no less crucial, and palaeotaxonomy no more dispensable. This is epitomized by recent developments in discussions on our species' origins and the extent to which Middle Pleistocene hominin forms represent distinct lineages. While it is tempting to think that progress in such debates is only hampered by the paucity of fossil and genomic data, we argue that problems also lie with unrealistic assumptions in theory. In particular, we examine ongoing discussions on whether H. sapiens and Neanderthal deserve distinct species status as a means to advocate for the necessity of reframing speciation in palaeoanthropology in a more biologically plausible way. We argue that available palaeontological evidence is best interpreted under a framework that sees speciation as an evolutionary process that starts in space, thereby involving a geographic dimension, and progresses in time, thereby involving a diachronic dimension, with an incremental accumulation of relevant characters at different phases of the process. We begin by discussing evidence about species-level differentiation of H. sapiens and Neanderthals and analyze major sources of taxonomic disagreement, before illustrating the potential of this perspective in making progress on the earliest stages of H. sapiens speciation within Africa.
