Correlation Analysis between the Maximum Number of Cell Types and the Density of the Transmembrane Gene Duplicates throughout the History of LifeThe estimates of the number of cell types in eukaryotes at different times in the past was derived from the work of Hedges et al. [23], and the corresponding density of duplicates was calculated by using linear interpolation in the time series inferred from the overall density trace (for details, see Protocol S1).