Laura van Holstein: "The Red Queen versus the Court Jester: Determinants of Speciation in Human Evolution"

Talk link: https://youtu.be/MISYTyWt5v0

Talk abstract: Many animal clades show a negative relationship between speciation rate and the number of closely related species, as competition for saturated niches places limits on clade expansion. Here, I track speciation rate across two hominin phylogenies, and show that Australopithecus and Paranthropus follow this general trend, but that Homo is fundamentally unusual in bucking it. Speciation is density-dependent in Homo, but the relationship is positive: the more species in the previous time slice, the higher speciation rate in the next. I test ecological and non-ecological routes Homo might have taken to escape competitive restrictions on speciation and suggest that is probable that the unique macroevolutionary pattern seen in Homo was shaped by range expansion and tool use. My principal argument, then, is that Homo is not just unique in a comparative context for its microevolutionary autapomorphies – reliance on lithic technology, capacity for long-range running and range expansion, unusually large brains, complex language, and so on – but that these characteristics, combined, produced hitherto unknown highly unusual macroevolutionary dynamics.