(A) Brain size deviation was calculated as the difference between the mean BayesModelS prediction (made while excluding all hominin data from analysis and using the alternate hominin phylogeny) and the observed value. Phylogenetic distance was measured as time since the shared ancestor of hominins and Pan at 9.28 mya. (B) Hominin portion of the alternate hominin phylogeny after δ transformation, with δ = 3.745 following the directional acceleration model. Among the PGLS models fit to this data, the directional acceleration model (AICc = −23.88) was favored, as it outperformed the the Brownian (AICc = −15.71), directional (AICc = −22.12), and accelerating (AICc = −22.38) evolution models. This model gave evidence for both evolution towards larger brain volume relative to body mass (slope = 0.06) and for accelerating evolution (δ = 3.745).