Fig. 2: Root-to-tip regression and date-randomization temporal test.

a Root-to-tip linear regression lines plotted either in blue solid line when integrating historical genomes (blue dots, n = 184), and in red dashed line when only computed from modern genomes (white dots with red line, n = 171). Gray areas (error bands) indicate 95% confidence intervals. Associated values are the linear regression equation, adjusted R² and p-value obtained from a two-sided Student test under the null hypothesis of a slope equal to zero, with (n−1) degrees of freedom (significant only when including historical genomes). b Evaluating temporal signal in the dataset by date-randomization test showed no overlap between the age of the root estimated from the real and date-randomized datasets (summed up in a single box) when historical genomes were included (left). Boxplots display the five following summary statistics: minimum, first quartile, median, third quartile and maximum of the 95% highest posterior density intervals. Statistics were computed from n = 10,000 iterations. Source data are provided as a Source Data file.