Distribution of C T substitution frequencies at the first position of the 5 end of sequencing reads from ancient ( n = 298, red) and present-day ( n = 943, blue) phage contigs. Box and whisker plots in c and d show median (centre line), upper and lower quartiles (represented by boxes), and highest (upper whisker) or lowest (lower whisker) value within a 1.5 inter-quartile range (IQR) while black dots indicate values outside of the IQR.
