Abstract
Two goals of evolutionary studies are to determine the relationships among organisms and the mechanisms by which change occurs (Sibley and Ahlquist 1986). For various reasons, both goals have been elusive. Relationships among species are often difficult to establish, especially because different methods of comparison may give different results. Such conflicting results are attributed to convergence, parallelism, reversals, and unequal rates of change. These problems are usually explained as the result of natural selection. By this reasoning, the best method for determining phylogeny would be to use some feature not controlled by selection.