Extent of domain duplication in different proteomes. The extent of duplication is estimated from the frequencies of observing domains in the different SCOP superfamilies and is shown as the fraction of total assigned domains for each proteome. The size of the human proteome is estimated at the number of protein sequences in the ENSEMBL dataset (∼29,000). Comparable results from frequencies of PFAM families (Bateman et al. 2000) are reported.