SINEs of the perfect character

In their quest to reconstruct the tree of life, evolutionary biologists are constantly looking for new sources of data. Morphological data have been applied to the phylogeny problem since the 1800s, and morphology continues to be the only source of available data on relationships for the vast majority of species on Earth, past and present. However, since the 1960s, molecular data have contributed an increasing fraction of the new information used to reconstruct phylogenetic history (1). Each new source of molecular information has provided a new perspective on evolutionary history, and each technique has a set of advantages and disadvantages. As with morphological approaches, most of these molecular techniques continue to be useful for specific kinds of problems. Nonetheless, almost every new molecular approach to phylogenetic inference has been ballyhooed as capable of “revolutionizing” the field. In truth, no one technique is a perfect solution for all phylogenetic problems, even though each provides us with a new perspective on evolution. Even the oft-perceived superiority of molecular data is largely a matter of timing. As Avise (2) has noted, imagine if we had studied the DNA sequences of organisms for decades without ever seeing a phenotype, and then someone suddenly discovered the morphologies and behaviors that DNA sequences specify! The sense that we were finally making real progress in our understanding of evolution would be at least as great as the sense of wonder and excitement that has accompanied advances in molecular biology.