It’s been a long time since I found a book as fascinating and as frustrating as Naming Nature: The Clash Between Instinct and Science by biologist and science writer Carol Kaesuk Yoon. Though it came out in 2009, I only recently tumbled to its existence (how it came to my attention is described later in this post).
This account of the history of scientific taxonomy from Carolus Linnaeus (1707-1778) to the present had me engrossed from the outset even as I began muttering objections, not to the story per se that she tells it, but to the dire impact she ascribes to it.
In Yoon’s telling, taxonomy, the systemic categorizing of entities in the natural world, had its formal, scientific birth in the early 1700s with the publication of Linnaeus’ Systema Naturae, which, through its multiple editions, displayed his effort to identify and label all known plants and animals. It is to Linnaeus that we owe the two-part nomenclature in use today which gives each species a unique name identifying genus and species. His taxonomic system was based on the appearance of organisms, an understanding that species were immutable, and on his intuition about which were related to others. Yoon writes, “He had, by his own example, validated the ancient notion that life should be ordered based entirely upon one’s individual perceptions.” (p. 49)
In time, the original underpinnings of this system would be challenged and largely overthrown, a movement fueled initially by Darwin’s theory of evolution which revealed how much the natural world was in flux and that species are not fixed. The goal of taxonomy changed, the order it depicted would come to be based on evolutionary relationships, a shift which, as related in Yoon's book, challenged most people's view of the world. In essence, after Darwin (1809-1882), “what evolutionary history tells us must be grouped together and what a person perceives should be grouped together in the natural order need not correspond at all.” (p. 76.) Yoon describes the various phases that taxonomy went through following Darwin, from evolutionary taxonomy to numerical taxonomy to molecular taxonomy and to cladistics. (More on the last shortly.)
A critical part of her thesis is that humans have a natural (evolution- and brain-based) drive to categorize and label what is found in the living world. This innate impulse evolved in our earliest ancestors who, in order to survive, needed to use their senses to quickly identify and distinguish between what was benign and what was toxic in the world around them – which plants were edible or poisonous, which animals were prey or predator, and which fellow humans might be friendly or hostile. Yoon posits, because our brains developed to provide us with this view of the world, we continue to want to make distinctions based on how we experience the world, using our particular constellation of senses. This sensory perception of the world is called our umwelt, a concept at the heart of Yoon’s treatise. (I wrote previously about the markedly distinctive umwelts of many different species of animals when I reviewed Ed Yong’s brilliant book, An Immense World: How Animal Senses Reveal The Hidden Realms Around Us (2022).)
Yoon argues that the history of changes in scientific taxonomy following Darwin is largely an account of battles to separate it from the human umwelt, to make it truly scientific and grounded in evolution. She writes that, in these fights, conscious or, often, unconscious adherence to our umwelt drove some taxonomists to hold tight to a classification system that treated species as definite and real, physical appearance as the best organizing principle, and intuition as a useful tool for organizing groups. After all, that is what our umwelt tells us about the living world – appearances are critical and groups are fixed. The taxonomists who adhered to those traditional methods based on general appearance of organisms fought the changes and lost.
The true villain in her piece are the cladists whose cladistic analysis (from the Greek clade meaning branch) came to the fore beginning in the 1970s, following the upheaval wrought by the numerical taxonomists (who drove as many different morphological characteristics as possible of different groups through computer algorithms to generate trees of relationships) and the molecular taxonomists (who relied on the study of what we cannot see – molecules – to determine the relationships among organisms).
Though Yoon describes cladistics, I had to look to additional sources to try and get a better grip on it. Not sure I succeeded. As I understand it, cladistics rejects general physical appearance as an organizing principle. In this system, only shared derived characters, that is, evolutionary novelties that are unique to an ancestor group and passed down to descendants, should be used to identify the evolutionary affinity among different taxa. A taxon that includes only those groups of organisms exhibiting the same evolutionary novelties is monophyletic, a clade. A clade is a “natural taxon which is a group of organisms that exists in nature as a result of evolution. Although there are many possible groupings of organisms, only a few groupings comprise natural taxa.” (E.O. Wiley, et al., The Compleat Cladist: A Primer of Phylogenetic Procedures, University of Kansas Museum of Natural History, Special Publication No. 19, October 1991, p. 3.) Groupings that are not clades may be considered “artificial” in this schema.
I found a discussion on cladistics that paleontologist Donald R. Prothero included in his book Bringing Fossils to Life: An Introduction to Paleobiology (1998) useful. He noted that hair and mammary glands are found only in mammals and, thus, are considered shared derived characters for all animals classified as mammals. Other features, such as four limbs and backbones, are not helpful in separating mammals from vertebrates because these attributes are found in a multitude of other kinds of animals, originating in some ancestor species to all of these animals. They can, however, be useful in identifying larger clades that include mammals, such as the vertebrates (which, in the graphic below, include sharks, frogs, and mammals). (Prothero, p. 47-48.) Here is a very simple cladogram reflecting this example (it is largely based on figure 4.2 in Bringing Fossils to Life, p. 48).
This cladogram is annotated to identify examples of evolutionary novelties (e.g., vertebrae) that arose in an unknown ancestor group and were inherited by descendants from that group. These diagrams do not identify a specific ancestor group in which shared derived characters arose because, in practice, such a group likely will never be known. Instead, the goal for such graphs is the identification of the evolutionary relationship among groups, that is, which cluster of groups form clades.
There’s the rub. Cladistics “does away” with the so-called artificial groups of organisms, those groupings that are not truly clades. In their drive to promote their taxonomic system, cladists were motivated to target their methodology on special groups of organisms whose demise as taxonomically valid groups were particularly stunning, groups that most of us outside of science and some within science had long held dear and, based on our umwelt, certainly real. The cladists’ most celebrated and reviled “kill” which they promoted repeatedly may well have been that of fish which, as a group, is not a clade and so, according to cladistics, is artificial, in other words, “dead.”
The death of the fish was a special moment each time it was an enacted because it was as grating, as disturbing, as umwelt-insulting as possible. It was, in essence, a direct attack on whatever was left of the taxonomist allegiance to their antiquated instincts. (Yoon, p. 259.)
The cladogram below, from The University of California Museum of Paleontology, shows the clade that consists of the ancestor group of all that we consider to be fish. Its descendants sharing its evolutionary novelties are shown. Unfortunately, among all these fish is a group (highlighted in yellow) that includes animals we certainly don't identify as fish: tetrapods. Tetrapods are four-limbed organisms which include myriad groups such as mammals and, thus, us. As a result, cladistics posits that fish, as the group is typically perceived, is not a valid clade because it excludes the tetrapods and their descendants. To make fish a valid evolutionary group, we have some less than satisfactory options. We might decide to include the tetrapods, thereby making us fish. We might remove the tetrapods, but, to do so, we would have to drop all of the animals that are shown to the left of the lobe-finned fishes and tetrapods in the cladogram, i.e., the hagfish, lampreys, sharks, and rays. And, so, fish are dispensed with by the cladists.
(The cladogram above is from A Fisheye View of the Tree of Life: What Is a Fish?, part of the University of California Museum of Paleontology’s Understanding Evolution website. It is reproduced under the Attribution-NonCommercial-Sharealike 4.0 Creative Commons License.)
It’s a fascinating story that Yoon tells, this conflict between an increasingly evolutionary-based taxonomy and the innate, human umwelt that sees the order of the natural world in mostly Linnaean terms. Most of the objections I had as I followed her narrative centered on how much she engages in hyperbole to oversell the apparent impact on the rest of us (those outside of science) of the triumph of the cladists.
In her telling, most of the ills that currently plague the human relationship to the natural, living world stem from that separation of the scientific view of that world from that of the human umwelt. She posits, “Taxonomists abandoned their umwelt, and we did so along with them.” (p. 283.) People, she argues, stopped caring about the living world largely because, as defined by the cladists, the natural order no longer squared with our umwelt. As a result, gone were the amateur naturalists who could name a multitude of butterflies or beetles and, in their stead, have come consumers who can cruise the malls and identify myriad products on the basis of their logos. As this has been happening, the natural world has been under siege with species disappearing at an accelerating and alarming rate and, she posits, we do not care because science has turned its back on our umwelt.
Really? Science dominates our consciousness to that extent? There are points at which I think she realized how much she may have gone overboard about the consequences of the rise of the evolutionary-based taxonomy, and decided to leaven her message with some additional forces that might have contributed to our purported disconnect from nature. Consider this passage which begins with her central message and then segues into a discussion of how more than taxonomy might be at work:
Maybe it's no coincidence that, as taxonomy’s relationship with the living world began to change in many ways, so did everyone else's. It wasn't just scientists who were stepping away from luxuriating in the sights, smells, and sounds of the living world. The rest of us were, too. The 1960s certainly wasn't an age of spending one's weekends collecting shells or butterflies. But even beyond the decline of pure natural history pursuits, whose once obvious appeal had become largely mysterious, other factors were conspiring to decrease our chances for interaction with the living world. The paying work that brought people into regular, intimate contact with nature – small-scale farming, hunting, and fishing – was on the decline, the inefficient individual replaced by much more efficient industrial scale machinery. (Yoon, p. 207.)
Frankly, I think she has it right at the end of that quotation: the rate of urbanization and industrialization probably has had much more to do with changes in people’s daily relationship with nature than did any of the musings of cladists.
I also wonder whether the loss of the human umwelt in scientific taxonomy can really explain why human beings might be so unconcerned and accepting, as Yoon sees it, of the decimation of different species. Wasn't it often so in the past? Even when taxonomy still largely enshrined the human umwelt, we drove countless species into extinction. Think of the passenger pigeon, for instance. Go back still further, to say, 52,000 to 9,000 BCE, well before we had science at all, when we were still thoroughly immersed in our umwelt for our very survival, and what do we find? Early humans across this span of time were most likely at the center of the extinction of the world’s megafauna. (See, for example, Hannah Ritchie, Did Humans Cause the Quaternary Megafauna Extinction?, Our World in Data, November 30, 2022.) We humans seemingly have for a very long time had no compunction about doing away with entire species. Cladistics doesn't really merit the blame here.
An unscientific sample of one (me) suggests how limited the impact of the cladists and the death of fish have had on our (my) understanding of the natural world. Earlier this year, I read science writer Lulu Miller’s widely acclaimed book Why Fish Don’t Exist: A Story of Loss, Love, and the Hidden Order of Life (2020), a book that (deliberately) defies facile categorization, flowing among genres: memoir (of finding personal and sexual identity), biography (of David Starr Jordon (1851-1931), a renowned ichthyologist and the first president of Stanford University, and a thoroughly despicable individual whose view of static categories within the natural order led him to eugenics), and popular science (of the death of fish).
Until I read Miller’s book, I was blissfully unaware of the “calamitous” consequences of the rise of cladistics, something that clearly had no impact on me. Was I previously aware of cladistics? Yes. Did my nascent understanding of cladistics somehow wrest me away from my love of natural history and my connections to the living world? No. I never felt it threatened my sense of the world around me. Even more damning, it was Miller’s book itself that alerted me to the demise of fish as a “real” category of organisms. So much for the impact (at least on me) of the “death” of fish.
Let me expand my unscientific sample of one to a larger, but still unscientific, sample of two by including Lulu Miller herself. She has written and reported on science for NPR, and currently cohosts NPR’s Radiolab; so, she’s presumably certainly well read and attuned to what is going on in the world of science. But she writes that her introduction to the cladists and what they did to fish was in fact Yoon’s book published in 2009. How can that be, if the triumph of the cladists in the 1970s and 1980s left all of us disconnected from nature and uncaring about its fate? I doubt that she was, and I know I wasn’t.
Nevertheless, despite my grumblings about Naming Nature, it merits a reading.
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