By Quentin Wheeler
A new book explores the scientific, and very human, drive to name and classify the organisms around us, but its conclusions about how best to do so miss the mark
[Published 7th August 2009 03:33 PM GMT] @ www.the-scientist.com
Carol Kaesuk Yoon's Naming Nature tackles the oldest profession practiced by people with their clothes on. Taxonomy is the science of species: discovering, describing, classifying, and naming the millions of kinds of organisms with whom we share our planet. Yoon laments the dwindling support and respect for taxonomy and associated losses that go far beyond science. But Yoon, a journalist and PhD biologist, also adds an interesting twist to her view of taxonomy. She examines the discipline -- from the ancient Greeks to the present -- through the prism of human umwelt, the ethologist's description of how organisms perceive the world around them.
Yoon draws upon data from disciplines as diverse as child development, anthropology, and neurology to support her arguments for the human umwelt. As a taxonomist, I was fascinated by her suggestion that umwelt helps explain conflicts among different schools of taxonomic thought. When evolutionary taxonomists clung to the idea of paraphyletic taxa (groups that include an ancestral species and some, but not all, of their descendant species), Yoon suggests it was their umwelt that held them back.
Although evolutionary biologist Ernst Mayr had acknowledged by the early 1980's that Willi Hennig's theory of phylogenetic systematics (which groups species based on shared derived charcters and emphasizes common ancestry among species or branching patterns) revealed evolutionary relationships, yet he still argued for paraphyletic groups -- e.g. Reptilia, which includes dinosaurs, lizards and crocodiles but not birds.
The extent to which his umwelt led him to cling to the traditional groupings is an open question, but there were other reasons too. Evolutionary taxonomy tried to indicate degrees of phenotypic difference as well as branching patterns. People could easily recognize many artificial groupings due to overall physical similarity. And a huge literature already existed using names like Reptilia and Invertebrata that would need to be rewritten. It is fascinating to contemplate the influence of umwelt in this resistance to change, but Yoon oversimplifies by discounting the conscious reasons that Mayr and others had for their objections to phylogenetic systematics.
There are other details of both theory and history that I believe Yoon simply got wrong. She suggests, for example, that the "species problem" -- answering the deceptively simple question, "what is a species?" -- is likely to never be solved. Following her discussion of Charles Darwin's barnacle studies, she leaves the reader with the impression that species designations are necessarily arbitrary. Theoreticians working on species definitions since Hennig have made great progress in presenting testable hypotheses by viewing a species as the result of evolutionary history rather than an outcome of one of the many processes associated with speciation, such as the ability to interbreed.
Good taxonomy has always involved separating species from species-in-the-making. This, in turn, depends upon a sophisticated set of theoretical arguments about characters that takes variation into account. Yoon and Darwin are correct that all species show variation, of course. That variation is the raw genetic material of natural selection. At the heart of good taxonomy, however, is distinguishing between characters that are informative at the level of species and within-species traits that are not.
I agree with the spirit but not the particulars of Yoon's conclusions. She hopes that humans regain a close, personal contact with biodiversity so that we can better appreciate and value other species and get behind the urgent need to ramp up both our conservation and exploration of species. Amen to that.
Taxonomy, however, has another role to play as we meet an uncertain environmental future. We need corroborated, reliable species and phylogenetic classifications if we are to efficiently expand our knowledge of millions of species and have a rich enough vocabulary with which to talk about them. Aside from technical disagreements about the history of taxonomy and how it ideally works, I find myself most in opposition to her conclusion that we submit to this ancient umwelt, follow our feelings, and use whatever names we choose.
This drains taxonomy of its power to help people learn, access, and enjoy species in a logical framework. It introduces the kind of postmodern relativism to nomenclature that denies that there is truth and knowledge to be found in Nature. Yoon's approach to taxa would unleash pre-Linnaean chaos and may even be welcomed by Creationists who would find justification for ignoring much of what we have learned about evolutionary history. The world really is not flat, regardless of what our senses tell us as we drive across Kansas. And "fish" really is an artificial grouping.
Taxonomists will find the treatment of their field superficial and troublingly inaccurate, but will be intrigued by Yoon's umwelt argument. The general reader interested in taxonomy should seek out additional treatments of its history. Everyone should listen to Yoon's advice to explore Nature and discover living things for themselves. The more astronomers explore the heavens, the more we appreciate the rarity of biodiversity, and the more urgent the need to explore and classify species becomes. As taxonomists organize and deliver increasing volumes of information about Earth's species via the Internet, the more democratic the science will become so that we can all indulge our curiosity -- and umwelt.
Naming Nature: The clash between instinct and science, by Carol Kaesuk Yoon, W.W. Norton & Co., New York, 2009. 352 pp. ISBN: 978-0-393-06197-0. $27.95 US.
Quentin Wheeler is University Vice President, Dean of the College of Liberal Arts and Sciences, and Founding Director of the International institute for Species Exploration at Arizona State University.
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