Ex-Googler James Damore gives a simple, tidy explanation for the underrepresentation of women in STEM fields: they have evolved to be better at and more interested in “empathizing” than “systemizing” – people rather than things. He calls upon “science” to make his feelings about men and women look more like facts that are solid and unassailable.

Look into his “science” and you find psychologists like Simon Baron-Cohen, who divide people up into simple and tidy “brain types”, using the language of the natural sciences to make their theories about the essential difference between men and women look more like facts that are solid and unassailable.

James Damore says we must “open our eyes to a more accurate view of the human condition.”

Simon Baron-Cohen writes that “as we discover the ultimate causes” of sex differences – i.e. “inborn biological factors” – some readers “may find things that they would prefer not to see” (The Essential Difference, p.11).

They claim, in short, that however much we might like to believe that men and women are equally talented at everything, “science” will expose the tough but simple biological truth: men make better scientists and leaders, while women make better nurses and mothers.

They reach for “science” to show that differences in the way men and women think are solid and essential.

But do the “hard” sciences really offer such simple, tidy categories? What kind of place (and how much space) is there for essentialism in the biological sciences today?

Let’s continue a moment with the species question, by way of example, and then I promise I’ll actually get on to the sex differences stuff.

As I suggested in the last post, most biologists called off the search for the essences of species long ago. Even Linnaeus, in his later work, had begun to doubt that species were completely distinct or that they reflected an unchanging essence. And then came evolutionary theory, the core premise of which is that species change over time. It was broadly agreed their essences were nowhere to be found. But then, what was a species, if it wasn’t defined by some essence that all its members shared?

So began the search for the new essence of the term “species.” What special trait is it that makes a species a species, instead of a genus or a variety or a type?

I grew up with the impression that a species was a group of organisms that could breed to produce fertile offspring. I also had the impression that this was an objective reality. I expected that most people in this day and age would have grown up with a similar idea, but just for fun I did a mini Facebook survey and offer the results by way of anecodatal evidence:

• “A more-or-less arbitrary grouping of individual organisms based on their genetic similarity/relatedness.”

• “Can produce fertile offspring.” (NB. This guy went to the same school as I did.)

• “A group of chemicals that share chemical structures and can react in the same way.”

• “Group of organisms capable of interbreeding and producing viable offsprings.”

• “A type.”

• “Superficially plausible, but actually wrong.”

• “Taxonomy is bullshit. Don’t even try to work it out.”

The fact is that there are a number of competing definitions, and none of them are completely satisfactory. This is sometimes known as the species problem. In his seminal 1942 work, Systematics and the Origin of Species from the Viewpoint of a Zoologist, Ernst Mayr discussed the different approaches, which he termed species concepts. I’ll briefly introduce three species concepts that are common and have been influential:

The Morphological Species Concept: organisms are grouped by structural similarity.

• This is a version of the old natural kind concept, where perceived similarity of type is what matters. The problem here is that structural similarities frequally do not correlate with how closely organisms are related, or whether they can interbreed. A Chihuaha and a Great Dane look less similar than a donkey and a horse, but the former are considered members of the same species whereas the latter are not.

• Another problem arises in deciding which characteristis should be compared to gauge simlarity/difference, and where to draw the species boundary-line when it appears that there are gradations or a continuum of similarity. Such decisions may be arbitrary.

The Biological Species Concept: a group of organisms that can successfully interbreed and produce fertile offspring.

• This is the concept that Ernst Mayr argued for.

• One limitation of this concept is that it doesn’t work for species that reproduce asexually – and that’s a hell of a lot of species. In fact, the majority of organisms on earth.

• The other major problem here is that it isn’t actually all that clearcut whether two populations can interbreed “successfully” or not. How many fertile offspring does it take to qualify? Does this interbreeding have to happen “naturally” – do the populations have to have access to each other in the wild? Does that mean that populations on different continents cannot be members of the same species?
  And then, we frequently discover that pairs of populations can interbreed when we thought they couldn’t. Does that mean they are varieties of the same species, then? No matter how structurally and behaviourally different? In that case, we might have to consider that lions and leopards are one species. We might even have to class tigers in that species too; it all depends on how fertile how many of these offspring need to be.

The Phylogenetic Species Concept: a group of organisms with a unique ancestry, i.e. sharing one branch of the evolutionary tree and closely genetically related.

• This definition came after Ernst Mayr and was supposed to address the limitations of the biological concept.

• Geneticist Eugene M. McCarthy has called it “a morphological wolf in genetic sheeps’ clothing” because, like the morphological species concept, it uses structural and genetic similarities/differences to gauge how closely related organisms are.¹

• And DNA doesn’t necessarily tell us everything. As botanist and geneticist Verne Grant puts it, “Many evolutionists originally anticipated that molecular evidence in general and DNA sequence data in particular would resolve uncertainties about evolutionary relationships, but this hope has not been realized.”²

• Assessing the similarity of DNA sequences is not always that illuminating. Sequence similarity doesn’t necessarily mean organisms can interbreed. Big sequence differences don’t necessarily mean organisms can’t interbreed. And, as with morphology, how do you decide how much similarity is required and how much difference allowed? The species boundary-line is often drawn quite arbitrarily across a continuum of similarity.

Species Monists insist that a single definition exists, or can and should be found.

Species Pluralists accept that there is more than one valid definition, but there is a broad spectrum of pluralism, from anything-goes (not all that influential) to the just-a-few-accepted-concepts (more mainstream). Some pluralist thinkers regard the different definitions as reflecting the different kinds of species actually found in nature itself; some pluralist thinkers regard the definitions as useful intellectual constructs.

The morphological and biological concepts were already competing in Darwin’s time, along with the old essentialism. Darwin himself emphasised different versions of the concept at different times, and actually seemed to think that the category could not be defined because it didn’t really exist.

In a letter to Joseph Hooker dated December 24, 1856, he wrote,

I have just been comparing the definitions of species … It is really laughable to see what different ideas are prominent in various naturalists’ minds, when they speak of ‘species’; in some, resemblance is everything and descent of little weight — in some, resemblance seems to go for nothing, and Creation [is] the reigning idea — in some, descent is the key — in some, sterility an unfailing test, with others it is not worth a farthing. It all comes, I believe, from trying to define the undefinable.

In On the Origin of Species he recalled

I was much struck how entirely vague and arbitrary is the distinction between species and varieties.³

Later in this work he concluded,

In short, we shall have to treat species in the same manner as those naturalists treat genera, who admit that genera are merely artificial combinations made for convenience. This may not be a cheering prospect; but we shall at least be freed from the vain search for the undiscovered and undiscoverable essence of the term species (p.484).

Elsewhere, referring to the biological species concept, he pointed out its tendency towards a logical fallacy known as begging the question or a chicken and the egg argument:

There is no way to escape from the admission that the hybrids from some species of plants are fertile, except by declaring that no form shall be considered as a species, if it produces with another species fertile offspring: but this is begging the question.⁴

In slightly more modern English: I declare that two species cannot produce fertile offspring together. So if two organisms previously considered members of different species do produce fertile offspring, I declare they are one species and my definition remains intact.

This rather neatly demonstrates the way that our definitions and classifications, though arbitrary, can create or select the data that fit them, and exclude any evidence to the contrary.

So, for example, if I declare that the “female brain” is not designed for “systemising,” and then am faced with a female who “systemises” well, I simply declare that her brain cannot be “female.” She must instead have the “male brain” in her female body. If my name is Simon Baron-Cohen I’ll say she is “atypical for [her] sex”.⁵ Like this I avoid confronting the possibility that my definition is flawed and its criteria arbitrary.

To summarise: Darwin recognised that the term “species” was an artificial intellectual construct, supposed to be convenient for discussion, that did not in fact represent an objective reality. He expected that biologists would soon all recognise this, and called off the search for the “undiscoverable essence of the term species.”

NB. To say that the term or the class “species” as an intellectual construct doesn’t imply that the organisms denoted by the binomials homo sapiens and rattus rattus do not exist. Neither does it imply that all organisms are equally close genetically, or can interbreed freely. This kind of thinking simply recognises that the term does not represent a single natural class as found in nature. Instead the one term is being made to represent several different kinds of natural group. It is a term we have inherited from a pre-evolutionary tradition, and if we hadn’t inherited it, we might not now invent it to describe the way that nature is organised (or disorganised).

But whether they agree with this philosophical position or not, and even if they are monists, most biologists (zoologists, taxonomists, etc etc.) do at least agree that the question is complex. It becomes perfectly clear when you look closer that nature is not divided into tidy categories. And even with all the tools we have at our disposal, we can’t always be certain who is related most closely to who.

Take the animal known as the red panda.

It has been very difficult for zoologists to decide whether this cutie is more of a bear or a racoon; in any case, its binomial Ailurus fulgens means “shining cat.” Check the footnote to read this taxonomical stray’s story.⁶

And what about the fertile offspring of lions and leopards? Or the fertile female offspring of a other big cat crosses? And female mules that can be back-crossed with a male donkey or horse?

And that’s just in the mammalian world.

As Ernst Mayr put it, “an outsider would never realize how many interesting cases of evolutionary intermediacy are concealed in the seeming definiteness of the species and subspecies designations.”⁷