a, PC3 and PC4 of the PCA based on 7,696 1:1 orthologues depicted in Fig. 1b (each dot represents the median across replicates), and scree plot describing the amount of variance explained by the first 10 principal components. b, PCAs of individual organs (n = 7,696 1:1 orthologues). c, Correlation of expression levels throughout development between human brain and the other organs (20,345 genes) (top), and between mouse liver and the other organs (21,798 genes) (bottom). Similar patterns were observed using other organs as the focal organ, and species. For human, the prenatal data are in weeks (w) postnatally; new, newborn; sch, school age (7–9 years); ya, young adult (25–32 years); sen, senior (58–65 years).