I'm coming to this debate late -- haven't caught up with Tweeters mail yet -- but I want to express a viewpoint similar to those that I think a couple of other folks (?Michael Hobbs, Doug Canning?) have at least implied in their responses. I think DNA is great stuff; as a molecular biologist, I've worked with it in some way all of my professional life. It makes us what we are, obviously. But I think biology has taken a seriously wrongheaded turn if the question of delimiting species has been turned into a question of the similarity or difference in DNA sequences. The link between DNA sequences and the final whole organism, especially one as complicated as a bird or mammal, is just too long and complicated and tenuous. The only species definition that makes any sense is one based on the question of interbreeding. (Irregular or complicated interbreeding, or interbreeding between groups that aren't sister species, just means that evolution is still in process and that nature doesn't always allow us humans to have neat, orderly classifications for everything.) Whether two organisms will mate depends on complicated matters of appearance and behavior, which can't be read off a DNA sequence. I believe DNA sequences, or DNA hybridization, can be used to make cladograms and to sort out phylogenies, but I sure as hell hope ornithologists aren't going to let themselves be bullied by champions of DNA For Everything into making their judgements about species limits just on the basis of sequence similarity.

Burt Guttman
The Evergreen State College
Olympia, WA 98505 guttmanb at evergreen.edu
Home: 7334 Holmes Island Road S. E., Olympia, 98503