Fig. 4: Predicting neonatal brain size from adult brain size in primates.

a Phylogenetic tree of primates including all taxa from which the predictive models are derived (black, n = 254) and all taxa for which imputed neonatal brain size (pink, n = 30). Silhouettes at the tips are not to scale, are purely for illustrative purposes, and are all obtained from phylopic.org. b A plot of the data used in the model overlaid with the predicted values from the phylogenetic inference model in pink. c Distributions of prediction errors (actual−predicted values) from our self-validation analysis (n = 45 taxa with known neonatal and adult brain sizes) using the three different inference methods (OLS: ordinary least squares predictive equations, green; PGLS: phylogenetic generalised least squares predictive equations, orange; phylogenetically informed predictions, blue). Boxplots elements are as follows: centre line, median; box limits, first and third quartiles; whiskers, 1.5 × inter-quartile range; points, outliers. Tighter distributions near zero indicate more accurate predictions than distributions skewed away from zero \({\sigma }^{2}\) = 0.012 for OLS predictive equation, 0.015 for PGLS predictive equation, and 0.008 for phylogenetically informed prediction).