Monday, June 24, 2019

Should we do away with the categories of Linnaean classification in biology?

Christie Wilcox, What’s in a Name? Taxonomy Problems Vex Biologists, Quanta Magazine, June 24, 2019.
arl Linnaeus was probably not the first scientist to realize the inherent connectedness of life on this planet. But he articulated and codified it. In the 10th edition of his Systema Naturae, published in 1758, he established a system of naming and organizing life that endures to this day — what we still call Linnaean taxonomy, although today’s system is somewhat different from the five-rank hierarchy he proposed. The principle is the same, though: Life is organized into nested ranks, with each higher tier representing a larger group of related organisms to which the species at the bottom belong.

This ranked taxonomy — domain, kingdom, phylum, class, order, family, genus, species — is foundational to biology pedagogy. Every student learns it, often through a mnemonic like “Didn’t Know Popeyes Chicken Offered Free Gizzard Strips” or “Dear King Phillip Came Over For Great Spaghetti.”

But a growing number of researchers think it’s time for taxonomy to move away from these ranks, or even abandon them altogether. “When a student has to learn it, it also suggests to the student that there’s something special about these groups,” said Andreas Hejnol, a comparative developmental biologist at the University of Bergen in Norway. Yet there isn’t.

The problem that Hejnol sees with the whole system is that the ranks don’t mean anything specific or uniform across all groups of life. Even though species is arguably the most important rank across multiple fields of biology, there are dozens of species concepts in use — and biologists working with different groups of organisms can’t seem to agree on just one. You might think that the other end of the hierarchy would be more settled, but it wasn’t so long ago that domains simply didn’t exist — the three domains we use today (Archaea, Bacteria and Eucarya) were only proposed in 1990. At that time, the top rank was kingdom, and there were five of those; now there are at least six, though some say there should be as many as 32. Similar ambiguities plague all the taxonomic ranks in between — even those often considered to be major, distinct and unambiguous, like phyla.
Color me sympathetic, and I haven't even read the article. But I do know something about classification and I've thought about this off and on. Glad to see that some biologists are at least thinking about it. 

Still, given how classification pervades the discipline, it's obvious that changing things, however sensible it seems in the abstract, would be an enormous pain in the posterior. Just how do you get everyone to agree to a new system? How would you propagate such a change and what would happen to the existing literature?

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