Patterson et al. consider studies from the period 1987-1992, including both plants and animals, but not unicellular organisms, which lack sufficient morphological characters for a useful comparison. Most of the discussion focuses on higher taxonomic categories, above the level of family. The degree of congruence between molecular and morphological phylogenies seems no better than reported previously in the 1987 book. Few taxonomic groups give completely consistent phylogenies when different methods are used. Disagreement seems to increase as more taxa are added, more characters are considered, and at higher taxonomic levels.
Molecular phylogenies are as likely to disagree with each other as are morphological phylogenies.
The authors' concluding statement suggests pessimism that evolutionists will ever be able to produce a single acceptable tree of relationships for all living organisms. The function of DNA has generally been seen as the production of proteins. Clearly, some DNA is involved in gene regulation, yet the function of a large proportion of the genome is still unknown. Among these are introns, satellites, 3' untranslated regions, short and long interspersed elements, and pseudogenes. Satellite DNA might play a role in holding the chromosome together, especially at its ends and at the centromere.