Results are for non-transmembrane pfams. (A) The brown linear regression was calculated for recent animal pfams (slope = −0.062, R2 = 0.0097, p = 6 × 10−7, n (number of pfams) = 2456), green for recent plant pfams (slope = 0.056, p = 0.1, n = 183), and black line over ancient pfams in all lineages (slope = −4.2 × 10−4, p = 0.9, n = 3102). Data underlying animal and plant curves is visualized separately in Figure 1—figure supplement 3. Slopes represent the decrease in average IUPred2 score, that is, the predicted propensity of the average amino acid to be disordered, per billion years. Each data point consists of the average across all instances of homologous pfams, across all species in which it occurs. Phylostratigraphy assigns these to age classes, dated using timetree. To help visualize the data, every age class is represented in the figure by a weighted box plot, where the width of the plot indicates the number of pfams in that age class. The median is shown in red, with the boxes representing upper and lower quartiles (the 75th and 25th percentile), and the whiskers indicating 9 and 91 quantiles. For age classes with only a single pfam, values are presented as small red dots. For clarity of presentation our plots do not show outliers, although we note that these are included in our linear regression models. (B) Phylostratigraphy slopes for pfams calculated over different subsets of the data are plotted with their 95% confidence intervals. The point colors correspond to the regression slopes in (A).