When people think of science, they think of physics or chemistry or astronomy, of particle accelerators, of racks of test tubes or giant telescopes. They don’t think of taxonomy; yet this less-than-glamorous science is at the heart of modern biology.
Taxonomy is not, as you might suppose, the scientific study of taxes. Instead it’s the science of classifying living organisms into hierarchical groups that represent the relationships among them. It’s been going on since the first humans started calling some living things “birds” and other living things “fish” to distinguish between them.
The ancient Jews had quite an extensive taxonomic system to help decide which animals could and could not be eaten. Aristotle resolved the living world into 14 groups, such as mammals and birds, and then arranged creatures within the groups according to size–ignoring an enormous range of other characteristics.
A 17th-century English naturalist, John Ray, was the first to try to classify living things based on their anatomical similarities, because, as he put it, “When men do not know the names and properties of natural objects…they cannot see and record accurately.”
However, the most famous taxonomist (which isn’t quite the oxymoron it may appear) was the 18th century Swedish botanist Carl von Linné, who founded the modern science of taxonomy by writing Systema Naturae. (Since he wrote in Latin, he’s better known by his Latinized surname, Linnaeus.)
Linnaeus invented many of the names that are still used today to describe the hierarchy of nature. The fundamental group is the “species.” Related species are grouped into a “genus.” Thus, horses and zebras are two different species, but they belong to the same genus, Equus. (Partly because Linnaeus wrote in Latin and partly because Latin, as a dead language, does not change, the scientific names of creatures are usually Latin or, at least, Latinized.)
Related genera, such as the asses and onagers, are grouped together into “families”–in this case, the Family Equidae. Equidae is then grouped with two other families, the rhinoceroses and the tapirs, to make up an “order,” Perissodactyla, the odd-toed ungulates. (All of these animals have either one or three toes per foot.)
Perissodactyla and all the other orders of hair-covered, milk-producing animals are grouped together in a “class,” Mammalia. Mammals are then grouped with the classes of other backboned animals, such as reptiles, into a “subphylum,” Vertebrata, which is part of the “phylum” Chordata, containing all animals which have a nerve chord at some time in their life cycle.
Finally, the Chordata are placed with all the other phyla of living creatures that are multicellular and “heterotrophic” (meaning they have to eat), into a “kingdom,” Animalia.
Each species has a two-word name. The first word is the genus; the second is species-specific. Thus, the common European starling goes by the scientific name of Sturnus vulgaris, Sturnus being the genus of starlings and vulgaris meaning “common.”
(These names aren’t written in stone. As classifications are revised or updated in the light of new data, the name may change. For example, Linnaeus designated the bluebell as Hyacinthus non-scriptus. Since then it has also been known as Agraphis festalis, Scilla festalis, Scilla non-scripta, Scilla nutans, Endymion non-scriptus, Hyacinthoides non-scripta and, currently, Scilla non-scripta again.)
Darwin saw in the successful Linnaean system further evidence for his theory of evolution, and neatly turned Linnaeus’s hierarchy into evolutionary trees. (Linnaeus himself believed his classifications were revealing the work of the Creator.) The explanation of why some organisms are more closely related than others is called systematics.
Today there is more than one approach to taxonomy. Traditional, or evolutionary, taxonomy, is based on Darwin’s feeling that classification should represent the genealogy of the organism. Gaining ground today is the cladistic system, introduced by German biologist William Hennig in the 1960s in an attempt to turn the “art” of taxonomy into more of a true, methodological science.
Cladists emphasize classifying creatures solely on the basis of their particular characteristics, without reference to how they may have evolved. Fossils can be classified using this same approach, but cladistic taxonomists avoid designating any particular fossil as an ancestor of a living form, because there is no objective way of knowing all the features a living ancestral form would have had.
Another method of classification called phenetics makes use of computers to compare vast numbers of characteristics to assess similarity. In this approach even the absence of a characteristic in two organisms counts as a similarity.
Maybe this all sounds a bit dry, and maybe that’s why taxonomy is not a glamorous science. But taxonomy really is the underpinning of biology, and its importance is thus hard to overstate.
As Robert M. May, an English zoologist, puts it, “Without taxonomy to give shape to the bricks, and systematics to tell us how to put them together, the house of biological science is a meaningless jumble.”
And as Tim T. Tokaryk, Paul C. James and John E. Storer, curators at the Saskatchewan Museum of Natural History, recently wrote in a letter to the Leader-Post: “If we ask how many species are near extinction in the rain-forests or what effect global warming has on various ecosystems, we must first find out which species, extinct and extant, there are. This is the job of a taxonomist.”
It may not be a glamorous job, but somebody has to do it!
