Those assuming the evolution of eukaryotic genomes has progressed upward in complexity may find the following abstract from PNAS1 startling: We use the pattern of intron conservation in 684 groups of orthologs from seven fully sequenced eukaryotic genomes to provide maximum likelihood estimates of the number of introns present in the same orthologs in various eukaryotic ancestors. We find: (i) intron density in the plant-animal ancestor [sic] was high, perhaps two-thirds that of humans and three times that of Drosophila; and (ii) intron density in the ancestral bilateran [sic] was also high, equaling that of humans and four times that...
