Divergence-time estimates for hominins provide insight into encephalization and body mass trends in human evolution

The authors apply a Bayesian total evidence dating approach to a recent hominin phylogeny, estimating that the origin of Homo probably occurred 4.3-2.56 million years ago. Ancestral state reconstructions show the onset of a trend towards greater body mass with the origin of the genus and gradual but accelerating encephalization rates throughout hominin evolution. Quantifying speciation times during human evolution is fundamental as it provides a timescale to test for the correlation between key evolutionary transitions and extrinsic factors such as climatic or environmental change. Here, we applied a total evidence dating approach to a hominin phylogeny to estimate divergence times under different topological hypotheses. The time-scaled phylogenies were subsequently used to perform ancestral state reconstructions of body mass and phylogenetic encephalization quotient (PEQ). Our divergence-time estimates are consistent with other recent studies that analysed extant species. We show that the origin of the genus Homo probably occurred between 4.30 and 2.56 million years ago. The ancestral state reconstructions show a general trend towards a smaller body mass before the emergence of Homo, followed by a trend towards a greater body mass. PEQ estimations display a general trend of gradual but accelerating encephalization evolution. The obtained results provide a rigorous temporal framework for human evolution.

Automated summary

The study applied a Bayesian total evidence dating approach to hominin phylogeny, estimating the origin of Homo probably occurred 4.3-2.56 million years ago. Ancestral state reconstructions revealed a trend towards increasing body mass and accelerating encephalization evolution. The results provide a rigorous temporal framework for human evolution.