a, Number of genes in each organ that evolved new trajectories across the phylogeny. Includes genes that differ between opossum and eutherians, for which the change cannot be polarized because of the lack of an outgroup. b, Distribution of trajectory changes among organs for the different species. The number of genes that changed in each organ is depicted in Fig. 4b. Humans show a relative excess of changes in brain tissues and a relative paucity in testis. **P = 2 × 10−5 for brain, P = 0.02 for cerebellum and P = 1 × 10−10 for testis (from binomial tests where the probability of success is derived from what is observed in mouse, rat and rabbit). c, Genes tested for trajectory changes (7,020 genes) in mouse (top) and human (bottom) have significantly lower tissue- and time-specificity than genes not tested for trajectory changes (13,325 genes in mouse and 14,778 in human, two-sided Wilcox rank-sum test). d, Genes with trajectory changes in mouse (top) and human (bottom) have similar or lower tissue- and time-specificity than genes with conserved trajectories (two-sided Wilcox rank-sum test). N.S., not significant. e, Number of organs in which genes evolved new trajectories in the different species. Box plots are as in Fig. 3e.