Origin of protein domains and domain combinations along the tree of life.

The total number of domains and domain combinations is 3464 and 116,400, respectively. Columns from left to right list the number of domains and combinations originated from each major lineage, the ratio of the number of combinations over that of domains, and the average number of domains per protein rooted at each lineage. Taxa are arranged according to their phylogenetic classification. Some nodes could not be evaluated since they derive from 0 or 1 domains.