A new book correctly criticizes the idea that some species are superior to others, but mistakenly claims that species aren’t real

January 29, 2023 • 10:10 am

The Berkeley News, the publicity site for the University of California at Berkeley, has a piece out announcing a new book that was published out in December (photo below). Since it was published by the venal and greedy Springer, the hardback of Speciesism in Biology and Culture will cost you only $159.

Click on the screenshot below to read about the book, which comprises nine essays rejecting humans’ view that we are the top and most important species, and that species can be ranked by their “superiority”. With that rejection I wholeheartedly agree. But there’s another theme, too: one which I think is misguided: species aren’t even real. Click below to read the article, which has a summary of the book.

Here are the book’s two themes:

In a new book, a group of scientists and philosophers places part of the blame on an attitude prevalent among scientists and the general public — the false belief that species are uniquely real, and that some species are superior to others.

To the researchers, this is analogous to racism — the fallacious belief that races exist as branches on the tree of life, and that some races are superior to others.

Now I agree that there is no hierarchy of species: we just happen to be the one that evolved a big brain with which we can control all other species, and an organ we can use to pat ourselves on the back as better than others. (A flea doesn’t have the capacity to see itself as superior to other species—but it can suck their blood!).

But the view that species are not “uniquely real” is a gross distortion. Species are far more real and discernible than human “races”, whose demarcation is somewhat subjective although even the “classic” races are not totally invented social constructs (they contain biological information).

If species weren’t real, however, there would be no problem of “the origin of species”, and nature would be a spectrum—a rainbow with no joints between its constituents. Orangutans, gorillas, and humans would all be arbitrary entities: “social constructs”. So would pigeons, starlings, robins, and cardinals. But I’m getting ahead of myself. A few more excerpts about the supposed non-reality of species:

Mishler has argued for decades against considering individual species as the most important grouping, particularly when discussing conservation. [JAC: actually, in the U.S. it is subspecies that are the units that must be conserved.] He laid out his arguments in a 2021 book, What, If Anything, Are Species? ( CRC Press), in which he proposed getting rid of taxonomic rankings altogether, including the binomial system for naming species that is used universally today. [JAC: As you know, this idea hasn’t caught on, nor will it.]

One key reason is that species distinctions are not equivalent across all branches on the tree of life. Bacteria that look identical may vary as much genetically as a dog from a cat, while some birds that live in totally different areas and look different can be nearly identical genetically. On the other hand, lineages — the sequence of organisms that have evolved from one another over millions of years — are consistent across all forms of life.

“Evidence shows that a species of amoeba does not mean the same thing as a species of fungus, animal or anything,” Swartz said. “And if species are not uniquely real, then where does that leave us? Is there anything that means the same thing across the tree of life? The answer to that question is: lineages. These are branches on the tree of life that maintain genealogical connections across time and space. They include children, or descendants, and their parents, or ancestors, on through animals broadly and their distant relatives. Lineages are branches across the tree of life.”

Throwing out the concept of species would eliminate the artificial dividing line that helps justify the belief that some species are more important. Instead, the authors maintain that humans are just one part of a genealogy connecting all living things. This interconnectedness forms an ecological web that sustains the planet and us, and that deserves to be protected equally with humans.

Mishler goes one step further, arguing that lineages should be respected — not for how they can benefit humans, but intrinsically, as part of the web of life. He detests the term “ecosystem services,” which implies that the natural world exists to service humanity.

. . .The authors point out that the standard definition of a species is a population that cannot breed with closely related populations. But Mishler said this definition is muddied by the fact that there is often wide variation within a breeding population; sometimes two separate species can and do successfully interbreed, and some species don’t breed at all.

. . .“Alan Templeton summarized it most succinctly: The trouble with species is too little sex and too much sex,” he said. “There are asexual groups that don’t do sex at all, but still have lineages. And then there are plants, like the orchid, which can just about be crossed with every other orchid, yet they’re bizarrely different from each other. So, reproductive compatibility, while a nice idea, just doesn’t work empirically.”

Species also can evolve because they get separated geographically or ecologically, not because of an inability to breed.

A more natural grouping is by lineage — ancestor-descendant pairs connected across time — or by clade, which consists of all the descendants of a creature.

Mishler and his colleagues have argued for years that species aren’t real, but their views haven’t gained any traction in the biological community beyond those few people who already reject the reality of species. Perhaps that explains this book.

The biological species concept (BSC), used by nearly all evolutionists, including me, is based on reproduction: a species consists of a group of populations whose members can exchange genes with each other, but cannot exchange genes with members of different species—where the different species live in the same area in nature—because there are barriers that impede genetic exchange between different species.

Now the entire first chapter of our book Speciation, by Coyne and Orr, is a defense of the BSC, a discussion of its problems (no, it’s not perfect), and an argument that it’s superior to all other species concepts because it gives us a handle on why organisms in nature don’t form a spectrum (see the Appendix for a discussion of alternative species concepts, including “lineage concepts” mentioned by Mishler).

First, the question of whether species are “real” is the same as the question “is nature a continuum or lumpy?”. That is, when we look at organisms like mammals or birds or trees in one place, do we see a continuum of variation that we can partition only subjectively, or are there discrete entities that are recognized widely as distinct? And for nearly all groups of sexually reproducing organisms, nature is lumpy. You already know this if you try to identify birds or mammals or other sexually reproducing organisms in the wild. We don’t have a spectrum of birds but, in one area, you see a series of discrete types that you can easily identify. Those groups (in one area; see below) are biological species: robins, starlings, pigeons, etc. etc., and are formally recognized with Latin binomials.  They are real, and you or Joe or Jill can easily slot what you see into a small number of bird groups—species. The lumpiness of nature in one area is, in fact, THE “species problem”, the problem that, despite the title of his book, Darwin didn’t answer. (He didn’t answer it because he had no knowledge of genetics and therefore no concept of reproductive barriers.) We need to explain why, in one area, we see a number of discrete forms and no intermediates (or only a few, which could be hybrids that are often sterile.)

The answer to the species question is that reproductive barriers, which are many (we have a chapter on each type in Speciation), keep species distinct by preventing any blurring that would occur with gene flow. Though hybridization between species in one area is more common than we used to think, in most groups it is rare, and if the hybrids are sterile or inviable, then they pose no problem for “blurring” species boundaries.

Now some caveats, for the BSC isn’t perfect:

a.) The BSC is meant to apply to sexually reproducing organisms because it’s based on genetic exchange between individuals or the lack thereof. In organisms like bacteria that are largely asexual, you can’t use it easily. Now whether those organisms form clumps as discrete as those seen in sexually-reproducing species isn’t clear: few people are interested in that topic, which I think is important. This issue is discussed at the end of the first chapter of Speciation.

b.) Two groups must usually live in the same place if you are to determine with certainty whether they are members of different species. If they do not form hybrids that are viable and fertile where they co-occur, they are different species. This is true, for example, of the lion and tiger, which used to co-occur in India before the lion was extirpated. They formed no hybrids in nature. (They sometimes do in zoos, but that’s because captivity can eliminate some reproductive barriers that occur in nature, like aversion to mating with other species. I call this the “prison effect”).

c.) If two similar species live in different places, it’s hard to tell if they’re different species or simply different populations of the same species. If you bring them together in the zoo or lab and they do not hybridize, or form sterile or inviable hybrids, then they are different biological species. But if they do form hybrids, even some fertile ones, the question is still unresolved, for, as I said, some true biological species hybridize in captivity but not in the wild. One can only guess in such circumstances. This kind of guessing is what biologists do when they designate very similar populations that live in different areas as “subspecies”. The “zoo or lab” tests are one-way: they can tell you that populations living in different areas are members of different species, but can’t tell you for sure that they’re members of the same species.

d.) Speciation is a process, usually occurring between geographically isolated populations of a single species. With no possibility of gene exchange, these populations begin to genetically diverge due to various processes like natural selection, sexual selection (a subset of natural selection), genetic drift, and so on. If that divergence occurs to the point that, when the different populations re-establish geographical contact, they do not exchange genes, then full speciation has occurred. But it need not occur: there are many time when populations aren’t isolated long enough to become reproductively isolated, and in that case they can re-establish contact and exchange genes. Those are not members of different species. (This re-establishment of contact is why human populations did not evolve into different species.)

Or, there could be some reproductive isolation but it’s not complete. In such cases we have to make a judgment, like calling them “incipient species” or “groups with incomplete reproductive isolation.” It turns out that there are evolutionary processes that, upon re-contact of incompletely isolated populations, can drive them, though natural selection, to evolve into different and full biological species. One such process is called “reinforcement”, and it’s been seen to work in both nature and the lab.

The upshot is that because the evolution of one species into two or more is a continuous process, there will be stages of the process in which there is some reproductive isolation but it’s not complete. (Geographically isolated populations will, if left long enough, nearly always become full species). That means that there will sometimes be problems establishing whether two populations are species or not. I like to say that spatially isolated populations become more and more “species-like” with time, and, when reproductive isolation is complete, finally attain the status of full biological species.

e.) The reality of species is also seen by common sense (the value of bird guides, for example), by the remarkable coincidence between indigenous people and outside scientists in recognizing the same groups existing in one location, and through using statistical methods to see if individuals fall into discrete phenotypic or genetic clusters. This is the very first topic we take up in our book, and provide ample evidence that clustering in one area is real, and that the same clusters are identified by both local residents and biologists from outside the area, establishing that the clustering is not simply the result of humans subjectively partitioning a continuuum of nature into discrete units.

If you think that species aren’t real, go outside for half an hour and look at birds. If you know your birds, do they form a continuum, or does each bird you see fall neatly into a group that has been recognized, described, and written up in bird guides? You already know the answer. Bird species are real, and that’s true in other groups of plants and animals.

I could go on, but if you can get hold of Speciation by Coyne and Orr, I’d suggest reading Chapter 1, which gives evidence for the reality of species. Since our book was taken over by Oxford University Press, it’s now as expensive as the one above, so try to get it from a library. Chapter 1 is, I think, accessible to the scientifically interested layperson. (The book, however, is written for professional evolutionists: grad students, advanced undergrads, or professional evolutionary biologists. I always tell my friends not to read it unless they’re willing to slog through the stuff meant for professional evolutionists.)

So yes, species are real in sexually-reproducing organisms, but there are intermediate cases because it’s a process that takes a lot of time—evolutionary time. Finding cases that are hard to decide does not negate the value of the BSC, for, in the end, it’s the genetic barriers between species that allow them to continue diverging from each other without “pollution” by genes from other populations. In other words, it is the evolution of reproductive barriers that produces the lumpiness of nature that we see in one area.

And that is the great value of the BSC: it explains why nature is lumpy, a question that wasn’t answered by evolutionists until around 1935 or so. It answers the species question, at least in sexually-reproducing organisms.  The concept of genetic barriers (reproductive isolation) gives a natural explanation for nature’s lumpiness, and thus the question of “the origin of species” in sexually reproducing groups boils down to the question of “the origin of genetic barriers. And that gives us something to work with at last! How do those barriers arise, and what is their nature? As I wrote in Speciation, I don’t know of a single study on the origin of species of plants or animals in nature that is not about the origin of genetic barriers and reproductive isolation. That’s how pervasive and useful the BSC has been!

As for the “lineage concept” of species, it’s deeply confused, and you can read the Appendix of my book to understand why. Just one point here: what lineages are we talking about? Lineages of genes are different from lineages of populations, and those differ from lineages of biological species. Species concepts based on using lineages of genes, for example, always wind up in a big muddle, and have not been used to answer the question of why nature is “lumpy.”  Insofar as lineages are constrained to remain separate, it’s because they’re reproductively isolated! But read the book to see more. Or look at any intro text on evolutionary biology, like this one.

In short, yes, I agree that no species is better than any other, or has any kind of natural hegemony over other species. That idea is crazy, though of course humans do kill and eat members of other species. But that doesn’t mean that we’re better than, say, cows—any more than lions are “better” than gazelles. So here I agree with the book’s authors.

But I think their view that species aren’t real is deeply misguided. It is, I think, an example of what I call “the reverse appeal to nature.” This is what I call the tendency to impose onto nature your own ideological or biological prejudices. The regular philosophical “appeal to nature” is the misguided idea that “what is natural is good”. (It’s similar but not identical to the “naturalistic fallacy,” which is “what we see in nature is what we ought to do.”)

The reverse appeal to nature simply stands that appeal on its head, saying “what we think is good must be what occurs in nature.” Another example of is using ideology to deny that there are two sexes in nature because you have an ideology that maintains that biological sex is a spectrum. You must thus claim that what exists in nature must be what your ideology tells you exists. This is why we see the pervasive ideological denialism of what is a palpable truth recognized by biologists. (And yes, there are only two sexes in humans and other animals.)

Perhaps the ideology behind the “species are not real” claim is that if you don’t think there should be a hierarchy of species, you can simply deny that species exist. But you don’t have to deny the existence of species to be kind to animals.

If you have questions about species or speciation, I’ll try to read the comments within a day and answer them. Or, best, consult this:

34 thoughts on “A new book correctly criticizes the idea that some species are superior to others, but mistakenly claims that species aren’t real

  1. Go outside and look at birds…and Yes, they do all come in this or that species, even if it’s sometimes hard to tell the immature ones. Around some parts here, though, go outside and look at the oak trees. Some are some identifiable species. Unlike the birds, though, they go in for hybrids. Or seem to. Anyway birds are a whole lot more obvious as species than some of the living things around us.

    1. Yes, oaks do hybridize (it’s in my book!) but somehow they manage to remain distinct in sympatry, probably because the hybrids are at a disadvantage (“postzygotic isolation”). What about primates, for example? Do you think that they’re not as distinct species as are birds? I suggest you look at Chapter 1 of our book, which deals with many things that are not as obviously different (there are lots of species that don’t look very different but are nonetheless distinct species).

      1. Plants really are a bit of a problem for the BSC, aren’t they? More and more evidence shows the ‘plant tree of life’ looks more like a network, with many major lineages having hybrid origins. Here is a forthcoming review I just came across:
        Deep reticulation: the long legacy of hybridization in vascular plant evolution
        GW Stull, KK Pham, PS Soltis, DE Soltis – 2022 – ecoevorxiv.org

  2. I always wonder about the Neanderthals commonly being classified as Homo neanderthalis. Clearly they interbred successfully with Homo sapiens, as we carry Neanderthal genes to this day. So why are they not considered a subspecies rather than a species on their own?

    1. I do think they’re a subspecies, and I’m not the only one. There was clearly gene exchange and the hybrids were at least partly fertile because we (“modern” H. sapiens) still carry their genes.

  3. I doubt that Brent (whom I know from graduate school and my early career) will get much traction in the effort to undo the binomial system and eliminate taxonomic rankings. Rankings become a challenge under a purely cladistic classification system, but a classification without a hierarchy would be unwieldy for sure.

    I’ll leave the matter of the reality of species to one side except to say that species of organisms are not unyielding, like chemical “species,” but that does not make them un-real. It might have been a better strategy for the book to focus on rejecting the idea of humans being at the top (a modern-day Scala Naturae) but to leave the species-reality matter for another time.

    On to Springer… . Their books are always super expensive; it seems that their primary market must be university libraries. Who else would spend so much? Oops. This just in. I see from Historian’s comment that the book is available for free!

    1. Allow me to prod you a bit. Do you think that gorillas are a real group distinct from humans? If so, why? Or are they simply an arbitrary group of animals designate subjectively as “gorillas”.

      1. Of course! Humans and gorillas are reproductively isolated from each other, and each is reproductively isolated from its closest living relative. As such, humans and gorillas have their own, unique evolutionary fates. They are ontologically real. (I know that “reality” itself is the philosopher’s playground, so I’m talking about things being real in the vernacular sense.)

        Before I left the field in 1995, I read everything there was about the biological species concept, allopatric speciation, sympatric speciation, peripatric speciation, etc. I read everything that Ernst Mayr wrote on the topic (well, not everything), and found his arguments to be very convincing. Lots of philosophers at the time (David Hull, Elliott Sober, and many others) were writing about—and defending—the reality of species as well. Your book too, of course, offers a vigorous and convincing defense,

        So, certainly, in my view, species in the form of reproductively isolated populations that cannot interbreed (or do not interbreed because of behavioral or other biological isolating mechanisms) are quite real. The genetic futures of two such populations—which have reached the stage of being two species—forever have separate historical fates. I don’t know how more real they can be.

        Bacteria, plants, and other organisms may be less clearly demarcated than sexually reproducing species but, in my view, they too are real. While there may be genetic exchange, this doesn’t mean that they don’t exist, only that they are more protean.

        I know I left a lot out of my original comment, as the literature is huge and I haven’t kept up in recent years. But if you ask me if species are real, my answer is yes.

  4. I will have to read that book (thanks Historian) but comments here will long have ceased by then, so here goes. Biology is a lumpy continuum in which the concept of species is very useful but it is not uniquely real because there are significant gray borders and it is not possible to draw a well-defined boundary.
    Over time, if one species evolves from another, how is it possible to decide on an absolute division?
    Over distance, if there is a ring species (if that term is still used), how is possible to determine an absolute line where one stops and the other starts?
    This is seen in some of the examples above – hybridization is rare but occurs especially in non-natural settings. There are incipient species where we aren’t sure.
    It’s the same with the concept of ‘life’ – a rock is not-alive but my cat (check, just sleeping) is alive but when does ‘life’ start or end and are viruses and similar things alive and when did life itslef start?


    1. If I’m following you, do you mean to say that in your view that there is not a distinct difference between any living and non-living things? No distinct differences between your cat and a rock? Or only that though there is a distinct difference between them, because there are border cases in which it is difficult to say if the thing is alive or not then all the clear cases are rendered invalid?

      Reality is very messy, and border cases between living / non-living and species A / species B can come down to such tiny or ambiguous differences that where exactly the line should be drawn is just not clear. But nevertheless there are perfectly clear, large clusters that are very real. There is no doubt at all that a rock and your cat are on different sides of the line. Just as there is no doubt that a cat and a bird are unambiguously members of different species.

      To my mind the border cases are not a problem but rather the “exceptions that prove the rule.” The messiness of border cases seems to me to be exactly what you would expect to see if the modern synthesis and the BSC were accurate models of reality.

  5. Mad a decently long comment, but an errant swipe of the finger caused it to vanish like the proverbial fart in the wind, so I’ll just say: good post, crappy book, Thanks for saving me $159.

  6. Another lovely tutorial and I appreciate it.

    If you have ideas on why few people are interested in the topic of “clumpiness/non-clumpiness” in say bacteria, your comments would be appreciated and thanked loudly here. On the other hand, you have things to do to keep us informed.

    Great post!

  7. Could you elaborate on one point? You agree with “the false belief … that some species are superior to others”. I am unclear what is meant here. Humans are clearly superior to all other species in some ways we consider important, including an ability to understand the physical world and to use that knowledge for our benefit. But we can’t fly very well, we can’t breathe underwater, and we can’t use echolocation as well as bats. How is ‘superior’ being used here?

    1. Might depend on who is making the claim. Certainly, religious people would argue from a different POV than another. I assume much of this is a holdover from ye olde Great Chain of Being, or just simple human arrogance coupled with the desperate need to feel special. Humans certainly rise to the top of the heap if you consider the ability to wipe out much of the earth’s biosphere on a whim, but that’s not much to be proud of. We are the only species to have a space program, as astronomically inclined are often heard to remark, but then most of us would be dead within a day of being lost in the remnant wilderness, while the “lowly” opossum goes bumbling along, happy as can be, but fails to negotiate traffic…granted, a surprising number of humans fail that as well. For me claiming humans are superior is a bit like saying “This is the BEST screwdriver!” Ok, but best for what job, what circumstances? Won’t do you a damn bit of good eating a bowl of soup.

  8. An elaboration and a caveat on points made by Jerry.

    The elaboration is that, for vertebrates, the US Endangered Species Act allows protection not just of subspecies, but of “distinct population segments”. So, American Crocodiles in Florida (the only population of the species in the US) can be protected without necessarily finding the whole species endangered. You don’t have to give a species or even subspecies name to a vertebrate to protect it. (Brent Mishler studies mosses, so needs a name to protect his organisms.)

    The caveat is that failure to breed in captivity is not definitive of being different species. Lots of species are hard to breed in captivity– it was decades before it was figured out how to breed cheetahs in captivity, and the status of king cheetahs not being a separate species was definitively resolved. The only dispositive result of captive studies is if the two forms breed, but the offspring are sterile or inviable.

    Jerry’s account of species and speciation in Why Evolution Is True is also excellent, and might be less daunting for some readers than Speciation.


  9. Species are historical entities. They’ll differ in their histories and so it’s difficult to come up with a single satisfactory definition of “species”.
    Perhaps a more fruitful way of looking at the species problem is to ask ourselves if species are real to their own members. Not as the result of any cognitive process, of course, but isolating mechanisms would seem to indicate that they are.
    Whatever happened to the idea of species as individuals? Ghiselin promoted this, as I recall.

    1. Thanks, that’s useful.
      I’ve been neglecting the issue for the last few years.
      Fortunately I recently unearthed my copy of Coyne and Orr.

  10. It is, I think, an example of what I call “the reverse appeal to nature.”

    This has also been termed the “moralistic fallacy”: what is desirable on moral grounds must indeed be the case.

    This has a corollary: if someone is claiming that X is true, it must be because they consider it morally desirable that X be true”.

    1. The corollary is exceedingly common in my experience and also one of the biggest obstacles to successful dialogue. Or honest dialogue, as I am convinced that often people knowingly use this fallacy because they have no intention of engaging in honest dialogue, but rather are intent on making you seem immoral to their audience, and therefore anything you say wrong, bad or invalid.

  11. In my opinion, a lot of this type of thinking is based on the false assumption that to state that X and Y are different implies that you’re also stating one is superior or inferior to the other. When and how did this type of reasoning start?

    1. It’s been going for a while, and explains why there’s opprobrium for even studying stuff like differences in mentation and preferences between men and women, or individuals between groups, or groups themselves. It’s the fear that finding differences automatically leads to bigotry. Of course it shouldn’t, but that mere fear is chilling research.

  12. I don’t understand why the authors even made their arguments, since their errors are easily discovered. Students in our freshman biology class are shown that there are real species in terms of reproductive isolation (“good species”), despite the fact that at the same time there are interesting cases that make it a bit complicated. The point there being that during early stages of speciation, which can be a protracted process and may never reach fruition, there are several ways in which different species concepts can give you conflicting answers. Cherry-picking the cases where speciation is not fully complete should not fool people with a little bit of background.

  13. Apparently even intelligent people have trouble with separating natural differences (like species, sex, or race) from the idea that they must be put (or will be put) into a hierarchy. Therefore, they think, if you want to eliminate the ideas that humans are the “highest form of life” or that men are better than women, come to recognize that it’s too blurry to distinguish between the two.

    This tendency partly comes from a human nature that likes to rank things, and, I think, partly comes from the Queer Theory insistence that everything is a “binary” — discreet and opposite categories created by language. The only way to break free of this is by “”queering” the boundaries by blurring them, or “transgressing” them by moving from one side to the other, therefore showing that they weren’t really real to begin with.

    The insistence that sex is a messy, unclassifiable “spectrum” is prompted by a desire to aid people who want to become some sex other than the one their biological reproductive system unfairly tries to force on them. I really hope (that is, I am of course assuming) that the authors of Speciesism in Biology and Culture are not self-identified “furries.”

  14. I can accept that humans are not superior. After all, a platypus would look down on us for having no electrical sensing ability whatsoever.

    However, it seems undeniable that humans ARE exceptional.

  15. What would be a non-speciesist course of action if, say, a human is suffering from amebiasis? Should we check whether the human or the population of amoebas represents more unique lineages before possible treatment?

  16. The picture from the book “Speciesism in Biology” was taken in Paris, in National History Museum, this is the entrance of “Paleontology Hall”. Each year I show this place to the students of Sorbonne University and I ask them “what do you think about this ?”…

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