Trilobite “horns” may have been used as weapons in male-male combat

January 19, 2023 • 9:15 am

Years ago I met Richard Fortey at the inaugural meeting of Spain’s new evolution society, and found him an affable and lovely guy. He’s a paleontologist and writer, and I had the pleasure of reading and giving a positive review to his first book, Life:  A Natural History of the first Four Billion Years on Earthwhich is well worth reading (he’s written several other books, including Trilobite: Eyewitness to Evolution (also a good read).

And it’s four trilobite species that are the subject of Fortey’s new paper coauthored with Alan D. Gishlick, a geophysical sciences professor at Bloomsburg University, in PNAS, a paper you can read for free by clicking the title below (it’s free with the legal Unpaywall app., the pdf is here, the reference is at bottom, and judicious inquiry might yield a pdf if you can’t see the paper). Trilobites are common fossils, and were marine arthropods that went extinct without leaving descendants.

The upshot is that Gishlick and Fortey analyzed fossils of one species of trilobite found in Morocco, deriving from the Devonian (400 million years ago). This species, Walliserops trifurcatus, had a long trident attached to the front of their bodies, and tried to figure out what it was for. They also found one adult individual whose trident was a bit deformed (see below). Their conclusion is that these were weapons used by males to fight with other males, almost surely to compete for females. They are, posit the authors, the arthropod equivalent of reindeer horns. The other possible functions (feeding, digging, etc.) were largely ruled out.

Read on:

Here are four species of Walliserops, shown below. All specimens bear a rigid cephalic trident. W. trifurcatus has a slightly recurved trident that bends upwards, while the other species have tridents more flush with the surface of the sediment (all captions come from the paper):

Four recognized species of Walliserops: A. trifurcatus, UA 13447 (topotype); B. hammi, UA 13446 (holotype); C. tridens UA 13451 (holotype); D. lindoei ROMIP 56997. Images taken from photogrammetric models. (Scale bar, 10 mm.)

The obvious question is: what is this damn thing for?  And there are several hypotheses, all assuming that the structure was molded by natural selection (which includes sexual selection). The authors find evidence against all but one possible function. Here are the alternatives (of course, it could have been used for several things, but it’s likely that selection was wholly or largely on one function). Indented bits are quotes from the paper. The rest of the discussion concerns W. trifurcatus:

A.) Defense. Perhaps the structure could have been used to ward off predators, like the spines found on other trilobites.  Here’s how the authors rule this out:

However, such a function would have been difficult given the overall anatomy of the trident and the trilobite. The trident is rigidly attached and cannot be moved independently from the cephalon; it could only be flexed in a dorsal-ventral plane by the trilobite raising and lowering its cephalon. This would create further difficulties since the long genal spines limit how high the head could be angled without lifting the entire body. The trident, therefore, could not be employed in a versatile way, nor be presented as to defend from a predator attacking from above or behind. This morphology is not consistent with a defensive structure.

B.) A feeding structure.  Doesn’t seem likely:

A second possible function for the trident would be as an aid to feeding. Like all members of the Phacopida, Walliserops was probably a scavenger/predator, and it might be considered as a possibility that the trident was a comparatively sophisticated sensory device concerned with early detection of prey species—such as buried annelid worms—which could then be grasped by the endopods of the ventral limbs.

C.) Sensory detection of the environment.  This is also deemed unlikely from inspection of the structure:

However, examination of the trident in optical and scanning electron microscopy failed to find the arrays of cuticular pits or tubercles usually indicative of the presence of sensilla in fossil arthropods. Most groups of trilobites include species with exterior exoskeletal pitting that is preserved even if the intracuticular canals have been removed by calcite reorganization—and there is no evidence of such exterior pitting on the trident of Walliserops. The absence of evidence for specialized organs on the tines makes it unlikely that it was primarily a sensory apparatus.

D.) A spear to pierce prey:  Unlikely because the structure was inflexible, so the animal would have no way of accessing speared prey.

E.) An apparatus to dig, perhaps for prey.  The way it’s shaped and angled seems to preclude this (remember, it’s slightly recurved upward; see below):

Another possibility is that the trident may have been used to agitate sediment to disturb prey items, which could then be trapped by the limbs. It is difficult to conceive of W. trifurcatus digging into sediment because to engage sufficiently with the substrate the cephalon would have to tilt at an angle greater than would be allowed by movement on the posterior occipital margin. Equally, if the thorax was arched, the pygidial spines themselves would dig into the sediment.

F.) A combat device on males molded by sexual selection mediated by male-male competition for mates.  The authors consider this most likely, especially because the tridents resemble the structure of male dynastine (rhinoceros) beetles, which use them to fight for females.

Here’s a picture of three of those beetles which have similar projections as do the Walliserops trilobites (the one at the extreme right).

(From the Natural History Museum): An image comparing the different beetle morphologies as they relate to fighting mode compared to Walliserops. © Alan Gishlick

The authors did a complex morphometric analysis of body and horn shape of W. trifurcatus, comparing it with living rhinoceros beetles to see if the trident could have been used for shoveling/prying, grasping, or fencing—the three types of male-male combat seen in living beetles. The analysis puts the trilobite in the group of living rhinoceros beetles whose males fight by fencing/shoveling: jousting with the structure in front and then trying to shovel the opponent over onto its back. I won’t go into the gory statistical details, which involve principal-components analysis, but the recurved structure of the trilobite’s “trident” is similar to that of shoveling, prying, and fencing beetles (left column: observed means of fighting of living beetles; center: the cephalic structures used; right: the species name [trilobite at the bottom]).

Cephalic structures of taxa treated in this research in lateral view showing the nature of the curvature and orientation of the tip of the active weapon and how it relates to its employment in combat.


As you see, and as the statistical groupings show, W. trifurcatus is similar to the structures used in rhinoceros beetles for fencing, prying and shoveling. Here is Gishlick and Fortey’s scenario of how the males battled it out in the competition to pass on their genes:

We would hypothesize a fighting scenario in Walliserops similar to that of Trypoxylus. The trilobites would meet and at first spar with their forks, pushing and poking. At some point, they would shift to trying to slide the fork under the other, in an attempt to flip them over. Given the morphology of Walliserops, flipping would be a very effective combat technique. Although the appendages of Walliserops are unknown, it is likely that they were like those of other phacopids in not extending beyond the carapace. This is seen in the Devonian Chotecops, asteropygines Asteropyge, and Rhenops, and recently described in three-dimensional material from the Silurian Dalmanites. Once the trilobite was inverted, righting would not be a simple matter, especially if the dorsally directed spines had snagged in the sediment. An upended trilobite would probably be even more helpless than a beetle in this position and thus excluded from sexual competition.

It might also be dead!

Now the first thing that struck me when I saw this paper was the question that would have occurred to many of you: WHERE ARE THE BLOODY FEMALES??  One of the signs of male-male competition is that the structures used to compete are present in males but almost never in females, as they’re of no use in that sex—and detrimental to fitness if you don’t use them. Male deer have antlers, females do not. Body size, used for combat in elephant seals, is huge in the males, and much, much smaller in females.  So if these trilobite horns really were tools used for the “combat” form of sexual selection (the other form, as pointed out by Darwin, is female preference), the females should be around but lack the ornaments. Where are they?

Gislick and Fortey suggest that the females were indeed around, but because they lack the tridents they have not been identified as females of Walliserops trifurcata:

Since the diagnostic synapomorphy [JAC: shared derived trait] for Walliserops is the anterior trident, it would be likely that the female of the species has been classified in a different genus. That leaves two possibilities: either the females of the relevant species are at present unknown, or they are known but placed in another trilobite genus within Asteropyginae.

That mandates a search for trilobites that resemble the males but lack the horns.  The authors raise another possibility: the females weren’t preserved or were offstage, living elsewhere, but this seems less likely:

If we extend the beetle analogy further, it is possible that the females are not preserved if some trilobites, like many dynastines, engaged in sex-specific aggregations; in this case, the females were not always present in the same locations as the males, although it is difficult to explain why the latter were selectively caught up in obrution events. [JAC: “Obrution” is rapid burial in the sediments, the way these creatures must have died and been preserved.]

I favor the “females not yet found” hypothesis. There’s one more hypothesis, which is mine: both males and females have tridents.  I don’t know why this would be the case, although you could think that it’s used to take other individuals out of action in conspecific competition for food. But that makes little sense.

Finally, the authors found one example of W. trifurcatus with a deformed trident, having an extra spike (a “quadent”?). Here it is on the right. Note that the branching pattern can be asymmetrical in the normal three-pronged structure).

Examples of branching patterns for the middle tines in W. trifurcatus; A. left branching (HMNS 2020-001); B. right branching (HMNS PI 1810); C. teratological example (HMNS PI 1811) showing a secondary branching of the left-branching middle tine. Images taken from photogrammetric models. (Scale bar, 10 mm.)

Because the individual on the right was an adult, Gishlick and Fortey suggest that the deformed structure did not prevent the bearer from growing up and thriving, and thus was unlikely to be used for some vital function like feeding. This adds a little more weight to the sexual-selection hypothesis.

The Upshot:  The authors’ analyses and explanations seem plausible to me, though they’d be even stronger if they could find the females. That might be tough: in living species you could find them by looking at mating pairs or even seeing that the DNA was nearly identical, but this isn’t possible with fossilized trilobites, especially because in some living and sexually dimorphic species the females look very different from males.  If the authors are right, and I think they are, then this quote from the paper is correct:

Walliserops provides the earliest example in the fossil record of combat behavior, very likely ritualized in competition for mates. Although fossil life habits are difficult to prove, the consilience of morphology, teratology, and biometric data all point to the same interpretation, making it one of the more robust examples of paleoecological speculation.

h/t: Matthew


Gishlick, A. D. and R. A. Fortey. 2023. Trilobite tridents demonstrate sexual combat 400 Mya. Proc. Nat. Acad. Sci. USA 120 (4) e2119970120 (in press).

Another dismissal of biological facts that go against ideology: The NYT claims that “maternal instinct” is a misogynistic myth.

August 28, 2022 • 11:00 am

UPDATE: In a comment below, Randolph Nesse, one of the founders of “Darwinian medicine,” cites a book I’d forgotten:

If only everyone interested in this topic could read “Mother Nature: Maternal Instincts and How They Shape the Human Species”, Sarah Hrdy’s 2020 book on the topic. And if only the NY Times would review such excellent science books so people would know about them! I am tempted to send Conaboy a copy.

Hrdy is a highly respected anthropologist, and you can order her book by clicking on this screenshot:

I highly doubt that Hrdy sees maternal instincts as pure social constructs designed to hold women down. I’m going to read it, and I hope Conaboy does, too.  Then we can expect her to retract her article (LOL).


Lately there have been a lot of articles trying to deny scientific evidence because, the authors claim, that evidence buttresses inequality. (One example is the widespread denial that sex in humans is a binary.)

The recent article below, from the New York Times (of course), is one of the worst of the lot. It bespeaks a lack of judgment on the part of the author—who ignores biology because of her ideology—as well as on the part of the newspaper, which failed to hold the author’s feet to the scientific fire. Let this post be my rebuttal.

Click on the screenshot to read.

Author Conaboy, who apparently hasn’t done enough scientific research, maintains that “maternal instinct” doesn’t exist, but is a social construct devised by men to keep women subordinate.

The immediate problem is that Conaboy never defines “maternal instinct”. It could mean any number of things, including a greater desire of women than men to have children, a greater desire of women than of men to care for those offspring, the fact that in animals mothers spend more time caring for offspring than do fathers, a greater emotional affinity of women than of men towards children (including offspring), or the demonstration of such a mental difference by observing a difference in caring behavior.

I will define “maternal instinct” as not only the greater average tendency of females than males to care for offspring, but also a greater behavioral affinity towards offspring in females than in males. The term involves behavioral response, not “feelings”, which are demonstrable only in humans. Thus one can look for difference in “parental instincts” across various species of animals. 

But even in this sense, Conoboy is partly (but far from wholly) correct when she discusses humans. It’s undoubtedly true that women were socialized into the sex role as offspring breeders and caretakers, with men assuming the “breadwinning” role. It’s also true that women were often denied access to work or education because their vocation was seen as “reproducer”, or out of fear that they would spend less time working and more on children, or even that they’d get pregnant and would leave jobs. Further, it’s also true that this role difference was justified by being seen as hard-wired” (i.e., largely the result of genes, which, I argue below, is true), and that “hard-wired” was conceived as “unable to be changed.” The latter construal, however, is wrong, and that is what really held back women. The socialization of sex roles, which still occurs, goes on from early ages, with girls given dolls and boys toy cars, though, as society has matured, we’re increasingly allowing girls to choose their own toys and their own path through life. I of course applaud such “equal opportunity.”

But to claim that women don’t have a greater desire than men to care for offspring, or have a greater emotional affinity towards offspring, is to deny biology, and evolution in particular. (I freely admit that many men love their kids deeply, and that some men care for them as much or more as do mothers, but I’m talking about averages here, not anecdotes.)

There are two reasons why Conaboy is wrong, and both involve evolution.

The first is theoretical, but derived from empirical observations. It thus explains the second, which is wholly empirical and predictive.  How do we explain the fact that, across the animal kingdom, when members of only one sex do most of the childrearing, it’s almost invariably the females? (Yes, in many species males share the duties, and in a very few, like seahorses, males provide more parental care; and there are evolutionary reasons for that.)

The reasons for the statement in bold above involves the biology of reproduction. It is the female who must lay the eggs or give birth, and there is no way she can leave her genes behind unless she does that. It’s easier for males to take off after insemination and let the females care for offspring. Given that females are constrained to stick with the fertilized eggs, their best strategy is to take care of the gestation and resultant offspring, which of course allows males to seek other mates. Not only must females carry the fetuses, lay the eggs, and so on, but they are also constrained to see out the pregnancy until offspring are produced and then suckle or tend them in other ways.  In some cases it’s the best evolutionary strategy for a male to stick around and share the child-rearing, but often it’s not.

This disparity in behavior holds not just in humans, of course, but in many animals: it’s a prediction—largely verified—of evolutionary psychology.

The difference in the amount of parental care given by females and males is seen throughout the vertebrates, as well as in many invertebrates (squid and some insects come to mind; see here for a summary in the latter group).

It is the female lion who takes care of the cubs (and hunts for them) while the males are indolent; most often it is the female bird who not only incubates the eggs but feeds the offspring; it is the mother elephant who tends to her young; it is the female primate who holds, cares for, and nurtures her offspring. This difference alone, caused by the constraints of different reproductive roles, will, over time, select for mothers to be more attentive to offspring than are the fathers, more worried about them, and more attached to them. As all of us know, it’s the mother bear who tends her young, and woe to those who get between a mother and her cubs! But where is Papa Bear? Well, he’s long gone. In my ducks, if you approach a young brood, the mother will attack you, but the father, even if he’s around, does nothing.

Note that I am just talking about behavior, not “feelings” here, as we can’t really know what a mother bear or a mother duck experiences in her brain. But these behaviors are clearly seen in primates like gorillas and chimpanzees, and here we can start advancing hypotheses about emotions.  Since I’m using maternal instinct as a behavioral phenomenon, it doesn’t really matter. What matters is that there is a strong regularity of behavior across the animal kingdom, one so pervasive that it demands explanation. And since animals don’t have humanlike culture, you can’t explain it by socialization. But can you deny, watching a female chimp cradle her young, that she feels something akin to love?

Of course to claim that a difference in sex and sex roles can cause a difference in behavior or emotions is anathema to “blank slaters” and those on the Left who flatly reject evolutionary psychology. And although Conaboy doesn’t go into the biology, this appears to be her view: there is no evolved difference in caregiving between men and women. Rather, differences in maternal and paternal behaviors must be the result of socialization.

And this brings us to the empirical point. Why, if “maternal instinct” is due entirely to socialization, is it is nearly ubiquitous among animals, causing female-specific nurturing and protective behaviors of offspring? Why, if Conoboy be right, are we the only species of animal in which those sex differences are due entirely to socialization? The parallels between humans and other animal species—especially other primates—is so strong that it would be foolish to deny that it says something about evolution. What it says is that human “maternal instincts” are partly hard-wired, and only partly socialized. As far as human emotionality is concerned, there are plenty of studies showing a difference in maternal vs paternal care due to hormones (here is one example), and they’re in the direction that evolution predicts.

Another example are studies showing that, when given a choice of toys, young female rhesus monkeys have a significantly greater preference for human “female” toys than do young male rhesus monkeys. (The toys are dolls vs trucks.) This preference of course is seen in human children, yet that could be, and has been, dismissed as a result of socialization. But rhesus monkeys don’t have that kind of socialization! The most parsimonious explanation is that monkeys, like us, have an evolved sex bias towards maternal instincts.

As I said, there are good evolutionary reasons to expect differences in maternal and paternal behavior, and we see those differences. While we can’t suss out “feelings”, it is likely that these behavioral differences are due to hormones, and in other apes we can guess that their “feelings” are not completely different from ours.

Conaboy, however, cavalierly dismisses the Darwinian explanation because of Darwin’s own sexism, as well as that of other evolutionists. Yes, it’s true that Darwin shared the sexism of his time, as have other evolutionists, but do we dismiss phenomena completely because of this? That would be foolish. Nonetheless, Conaboy does:

In the 1800s, Charles Darwin and other evolutionary theorists upended how we thought about human nature, shifting the focus from faith to biology.

And while one might have expected such a shift to dispel longstanding chauvinistic ideas about women and motherhood, the very opposite happened. Within his revolutionary work, Darwin codified biblical notions of the inferiority of women and reaffirmed the idea that their primary function is to bear and care for children.

“What a strong feeling of inward satisfaction must impel a bird, so full of activity, to brood day after day over her eggs,” Darwin wrote in “The Descent of Man, and Selection in Relation to Sex” in 1871Observant as he was, Darwin apparently ignored the hunger of the mother bird and the angst of having mouths to feed and predators to fend off. He didn’t notice her wasting where wing meets body, from her own unending stillness.

Women are specialized to care for other humans and men to compete with them, he explained. By that basic fact, he argued, men achieve “higher eminence” in virtually all things, from the use of their senses to reason and imagination.

As more women demanded their own identities under the law, social Darwinists seized on this idea as justification for continued male dominance. Among them was the English philosopher Herbert Spencer, who wrote that childbearing extracts “vital power” from women, stunting them emotionally and intellectually.

Note that Conaboy challenges Darwin by pointing out the travails that beset a mother as opposed to a father (this is also a big part of her objection to “maternal instincts” in humans). But she fails to point out that there are costs to child-rearing, but there are also costs to abandoning or ignoring children, and the former costs are greater than the latter. Yes, a mallard hen loses up to 30% of her body weight while incubating her eggs over a month, but she gets a healthy brood from that behavior. If she leaves the nest to eat and drink, she loses her brood entirely.  Genes that favor maternal care and concern will be favored. The notion of evolutionary tradeoffs—that a behavior can have costs and benefits, but will evolve if the reproductive benefits outweigh the costs—is something that apparently didn’t cross Conoboy’s mind.

Why is Conaboy so dead set against the idea of a “hard wired” (i.e., partly genetic) difference between men and women? For the expected reasons: she sees such differences as buttressing sexism, and so biological facts must take second place to her ideology. And, as I said, it is the case that scientists and others have used biology to justify sexism. But that doesn’t mean that the facts are wrong, or don’t give us insight into the evolution of sex-role differences.

Here are a couple of Conaboy’s statements showing the ideological basis of her objection to biologically based maternal instincts:

Where did the idea that motherhood is hard-wired for women come from? Is there a man behind the curtain?

In a sense, there is a man behind the curtain. Many of them, actually.

The notion that the selflessness and tenderness babies require is uniquely ingrained in the biology of women, ready to go at the flip of a switch, is a relatively modern — and pernicious — one. It was constructed over decades by men selling an image of what a mother should be, diverting our attention from what she actually is and calling it science.

Yes, sex role differences and behaviors, like the existence of two sexes themselves, must be dismissed because they go against what is an antiscientific, liberal, blank-slate ideology. When the facts are inconvenient, deny them and invoke bigotry.

Conaboy brings in religion, too, which of course has buttressed sex-role differences:

Modern Christian archetypes of motherhood were shaped by two women. There was Eve, who ate the forbidden fruit and in doing so caused the suffering of every human to come. And there was the Virgin Mary, the vessel for a great miracle, who became the most virtue-laden symbol of motherhood there is, her identity entirely eclipsed by the glory of her maternal love. Mary’s story, combined with Eve’s — unattainable goodness, perpetual servitude — created a moral model for motherhood that has proved, for many, stifling and unforgiving.

But religion’s own stereotypes aren’t independently contrived, but themselves come from sexism built by humans into a faith that is seen to create a harmonious society.

Others to blame for the “myth” of the maternal instinct are conservatives, another reason to dismiss the reality of that instinct:

Today, many proclaim that motherhood is neither duty nor destiny, that a woman is not left unfulfilled or incomplete without children. But even as I write those words, I doubt them. Do we, collectively, believe that? Maternal instinct is still frequently invoked in science writing, parenting advice and common conversation. And whether we call maternal instinct by its name or not, its influence is everywhere.

Belief in maternal instinct and the deterministic value of mother love has fueled “pro-family” conservative politicians for decades. The United States, to its shame, still lacks even a modest paid leave policy, and universal child-care remains far out of reach.

. . . Belief in maternal instinct may also play a role in driving opposition to birth control and abortion, for why should women limit the number of children they have if it is in their very nature to find joy in motherhood? A 2019 article published by the Ethics and Religious Liberty Commission of the Southern Baptist Convention, a Christian anti-abortion policy group, claimed that “the ultrasound machine has been the pro-life movement’s strongest asset in recent years” because once a woman is informed of her pregnancy, “her maternal instinct will often overpower any other instinct to terminate her pregnancy.” Why, then, should the law consider the impact of pregnancy on the life of a person who has the full force of an instinct stronger than “even fear itself” to gird her in the task?

I am course am not defending these statements, which do derive from sexism and misogyny. What I am saying is that Conaboy uses this kind of ideological and political argument to dismiss biological explanations for maternal instincts.

I won’t go into Conaboy’s description of the difficulties attending human childbirth, including postpartum depression, physical pain, and sleeplessness. Every mother knows what Conaboy is talking about. But it has no bearing on whether maternal instincts are a myth or a social construct of the patriarchy.

Finally, I want to bring up one other misrepresentation by Conoboy: the idea that there’s a big difference between “hard-wired” differences between the sexes versus differences that emerge later, after life experience. Here’s what she says:

The science of the parental brain — much of it now the work of female scientists who are mothers themselves — has the potential to pull back the curtain, exposing old biases and outdated norms, revealing how they are woven throughout our individual and societal definitions of mother or parent or family, and offering something new.

Using brain imaging technology and other tools, and building on extensive animal literature, researchers around the globe have found that the adaptation of the human parental brain takes time, driven as much by experience — by exposure to the powerful stimuli babies provide — as by the hormonal shifts of pregnancy and childbirth.

But surely environmental cues, like exposure to one’s own child, which is “experience,” can also activate hard-wired genetic differences between male and female behavior. (Let me emphasize that by “hard-wired” I do not mean that a behavior is always seen in one sex or the other; what I mean is that there are influences of genes on an average behavioral difference between men and women.)  It is entirely possible that the sight of one’s own infant can activate other evolved pathways that produce “maternal instincts”. (See here for one paper on this topic.) This is similar to human children born with the genetic ability to learn semantic language, but they can’t express that ability until they actually hear spoken language. Thus we have an evolved trait that requires experience to be expressed.

In the end, in her attack on sexism and its attendant limitation of women’s opportunities (a view I share), Conoboy is forced to deny all the facts of biology, even dragging in the much beleaguered Darwin for a good drubbing. But she hasn’t done her homework. If she had, she’d see that maternal instincts are not limited to humans, but are widespread among animals. And she’d see that there are good evolutionary reasons for such instincts—reasons that, in our species, could lead to a difference in feelings towards infants.

I’m sick to death of people either ignoring or denying the facts of biology when they’re ideologically inconvenient.  But that whole strategy fails for two reasons. First, the truth will out. In fact, we already know that Conaboy is wrong.

Second, it’s a terrible strategy to dismiss empirical data on ideological grounds. Far better for Conaboy to admit that sexism plays a role, but so does biology. There is nothing shameful in admitting that much of the “maternal instinct” is evolved. That admission does not force us to view women as inferior, nor to treat them as inferiors.

Finally every woman who chooses not to have a child because she has other priorities demonstrates that evolved tendencies need not compel our behavior. They can explain it, but that’s different from making it into an “ought”.

How Darwin caused global warming with his theory of sexual selection

July 9, 2022 • 12:00 pm

Yet another letter has appeared in the Guardian about Stephen Buranyi’s misleading “long read” on the site, “Do we need a new theory of evolution?” (Buranyi says “yes”). I’ve mentioned the problems with Buranyi’s article before, and three of us even wrote a letter about the article’s flaws that the Guardian published.

Apparently, though, the fracas hasn’t died down, because another one just appeared, this time on sexual selection. The letter is by anthropologist Heather Remoff, who wrote a book on sexual selection mentioned at the bottom of her letter.

Here’s the letter (click to go to the Guardian site), and my take on it is below:

There’s a lot to “unpack” here, and I’ll try to be brief.

First, the letter doesn’t address Burayni’s claims, which was that the modern theory of evolution was incomplete and perhaps obsolete. He was not referring to Darwin’s theory of evolution but to Darwin’s theory as it has been updated and expanded in light of modern research. Darwin’s failure to understand everything does not mean that the modern theory of evolution is woefully lacking, for we’ve had more than a century and a half of work on evolution since The Origin.

Ergo, showing that Darwin’s theory of sexual selection was incomplete—and yes, it was his theory, rejected even by A. R. Wallace (except in humans!)—does not support Buranyi’s thesis. That theory was published in 1871, and now it’s 150 years on. Modern evolutionary biology has added tons of knowledge and theory about sexual selection. There are entire books on the topic (here’s one) that go far beyond Darwin’s ideas. But showing that “Darwin’s theory was incomplete” doesn’t say anything about the modern theory of evolution, which is what this whole controversy is about.

Darwin actually had two theories of sexual selection, one involving male-male combat for females, and the other involving female preference for “beauty”. The former theory, which Darwin called the “law of combat”, explains the evolution of weapons like antlers in male deer—weapons far less developed in females because they’re not used.  Darwin’s second theory is that females have an aesthetic sense that males appeal to with ornaments, striking colors, extreme behaviors, or lovely calls. This causes female-imposed natural selection on males, which, thought Darwin, explains sexual dimorphism in appearance, behavior, calls, and so on.

Note first that, contra Remoff, female preference was already a crucial part of Darwin’s theory, for without that preference we wouldn’t have the striking sexual dimorphism we see in many animals. Even though male-male competition remains an important explanation for male-limited weapons or competitive behaviors, Darwin had already diagnosed a large portion of the sexually dimorphic world using the lens of female preference.

But Darwin’s theory was incomplete in a way Remoff fails to mention. Exactly why do males compete for females? Darwin had no answer, and you don’t find an answer simply by viewing the issue through the female lens. In general, biologists agree that sexual selection results from this:  female investment in offspring is often much larger than that of males. When females have to do the hard work of gestation and rearing of offspring, as well as contributing metabolically expensive large gametes (eggs), while male investment is often limited only to a small amount of tiny sperm, an asymmetry in the interests of the sexes arises. Evolutionarily, males can leave more of their genes by copulating with any female they can, while it pays for females to be choosy about her mates, since once she mates, she’s made a huge investment that has to be tended. A good choice by a female often means her offspring have a better change of surviving, ergo it pays to be picky.  A male fly can mate with 20 females in a few days and have 20 batches of offspring, but a female fly who mates with 20 males within a few days doesn’t have many more offspring than if she copulated only once. It thus pays the males to be profligate and the females to be choosy.

I often use this example in evolution class to show the asymmetry (see this page for the records). This is what your body is capable of producing if you’re a woman or a man:

Record number of children produced by one mother: 69 (many twins and triplets birthed by a Russian woman)

Record number of children produced by one father: 1000-2000 by Genghis Khan (estimated) or, in more modern times, over 868 fathered by Moulay Ismail Ibn Sharif, a Sultan of Morocco, in the 18th century.

A male can have more than ten times as many offspring over his life than can a woman! Of course the average number of offspring has to be the same for men and women (after all, each child has one mother and one father), but the variation is such that while women produce relatively comparable numbers of offspring, a lot of males produce just a few and a few males produce many. That is, males have a much higher variance in offspring number. And that is the basis for sexual selection. (This difference in variance is seen in humans as well as in many other species.)

The asymmetry between the sexes, then, rests on the best way to choose. For males it’s not evolutionarily “wise” to be choosy (I am generalizing here, for of course there are cases in which males should also be choosy), while for female it pays to make sure you choose well, as you don’t have as many shots as being a parent. As I said, this is a short explanation for sexual selection that has exceptions, but it’s the going explanation for why, when the sexes differ in ornamentation, behavior, or calls, it is males who show elaborated traits.

This asymmetry is critical in understanding the whole process of sexual selection, and it rests not on seeing it through a female lens, but seeing it through a lens that looks at what both sexes have to gain from behaving in various ways. In the end, it’s largely based on gamete size. That was what Darwin missed, but we understand it now and can test it.

Further, since Darwin’s time we have new theories of sexual selection that have been mathematically elaborated: the runaway model (Richard Prum has used this to update Darwin’s “beauty” hypothesis), the “honest signalling” model, the “sexy son” hypothesis, and so on. Some of these models overlap.  All of them consider female preference.

Now I’ve said in the past that, in my view, one of the contributions of the “female view” of biology has been an increased emphasis on female choice in sexual selection, for the process involves an interaction between males and females. Some women (but not solely women) helped direct research by emphasizing female preference. And that’s understandable; you don’t want your sex and its importance in evolution to be overlooked.

That said, though, both men and women have made important contributions to the modern theory of sexual selection; it was not incomplete because the “female lens” was totally overlooked by patriarchal male biologists. And, as I said, female behavior—aesthetic preference—was absolutely critical for the “beauty” aspect of Darwin’s original theory.

As for the “genetic breakthoughs” that have led to a new understanding of sexual selection, particularly when viewed through that female lens, I am stymied. I don’t know what breakthroughs Remoff is talking about. Perhaps she’s referring to this:

The evolutionary moonshot that enabled Homo sapiens to go where other species have failed to follow has its roots in a reproductive mutation – concealed ovulation and continuous sexual receptivity – that dramatically increased the strategic agency employed by females.

Concealed ovulation and continuous sexual receptivity (the latter is possessed by many animals) are not “mutations”; they are traits, likely ones that arose via many mutations of small effect. And yes, these traits have obviously changed the playing field for sexual selection. But whether they have been  “moonshot” that has enabled us to go where other species have not, well, other species have had their own “moonshots”, like hypodermic insemination in some invertebrates, the “pseudopenis” of the female hyena,”and the male pouches of pipefish and seahorses.

The last trait gives male seahorses most of the investment in offspring (males, in effect, get “pregnant”, and females, who can produce lots of eggs, must compete for limited male pouch space). The result that in this group it’s most often females rather than males who are ornamented. This reversal of investment, coupled with a reversal of the sexual dimorphism, is striking support for the “differential investment” theory of sexual selection.

Sexual selection operates in different ways in different species, and, truth be told, we don’t understand the details that have led to the evolution of most sexually dimorphic traits. not involved in male-male competition. We know the basis for the evolutionary process—differential investment in offspring—but we don’t know why particular traits are chosen and whether they are indicators of fitness or of something else. If you ask me why the peacock has a long tail instead of a big head crest, and what information that elaborate tail conveys to females, I wouldn’t be able to tell you. We do know that the more spots a male peacock has on his tail, the more likely he is to be chosen as a mate, but we don’t know the advantage accruing to females that have such a preference.

And no, sexual selection does not “establish the origins of everything that defines human exceptionalism”. Semantic language? Bipedality and manual dexterity? Our remarkably complex brain? Did all those traits rest on sexual selection? I think not.

Remoff ends with a paragraph that is pure hyperbole:

Why does all this matter? Because humans are facing an environmental disaster of our own making. Only by developing an accurate understanding of the factors that shaped human species-specific behaviour will we be able to avert the rapidly approaching climate apocalypse. Sexual selection may have shaped us, but our failure to take an unbiased look at ourselves could be handing natural selection the power to eliminate us.

Will understanding sexual selection, or human evolution in general, help us stave off climate change? Again I think not. Only by limiting carbon emissions will we be able to avert climate change. And that does not depend on understanding human evolution, much less sexual selection.

In the end, Remoff is tilting at two windmills that have already fallen. Her attack on Darwin is wrongheaded since Darwin’s correctness is not the issue in Buranyi’s piece and because female preference was already a crucial part of Darwin’s theory. And her claim that it was only the “female lens”, used recently, that helped us understand sexual selection, is also misleading. Female preference has been considered by evolutionists since 1871.

Scientific American attacks the “cult of the penis”

March 9, 2022 • 12:15 pm

There’s a new Scientific American article that presents some interesting biology, but does it tendentiously, for its aim is to show, by citing a few cherry-picked examples of odd biology, that interest in the penis among biologists, and the relative neglect of the vagina, reflects the patriarchy. It’s time, says author Rachel Gross to take the penis off its pedestal.

Now I freely admit that males often have an obsession with penises and their size, but I don’t think that the study of animal penises, as opposed to vaginas, reflects the patriarchy, despite a Vox Magazine article called “How a pseudo-penis packing hyena smashes the patriarchy’s assumptions.” (Read Steve Gould’s explanation of the spotted hyena female’s “pseudopenis”, a modified clitoris, though Gould’s hormone-based explanation is probably wrong.)

Gross’s article is loaded with examples of the naturalistic fallacy (or should I say “phallusy”?)—the idea that we can derive lessons about what is “good” or “moral” in humans from observing the behavior other species that lack our kind of culture (i.e., all other species). We may learn something about the evolutionary roots of our behavior, but not its lessons for sexual equality.

Click on the screenshot to read:

Here’s one example from the article, which begins by discussing two new books, Phallacy: Life Lessons from the Animal Penis, by Emily Willingham, and GUYnecology: The Missing Science of Men’s Reproductive Health, by Rene Almeling:

. . . the flashy focus on the male member serves as a Trojan horse (pun intended) for a very different message: that a culture of phallus-worship has slanted the science in crucial and sometimes unexpected ways. On the one hand, we’ve inflated the role of the penis in genital evolution; on the other, we’ve left the male contribution to infertility, genetic abnormalities and other reproductive consequences unexamined. The result is stunted, lopsided science that shows only one side of the story.

But if this all be motivated by the patriarchy, why are medical problems with male genitalia neglected and “unexamined”? But here’s one example:

Consider that myriad beetle species are classified solely by their penis shape, while the true breadth of vaginal diversity has yet to be explored. This tradition has deep roots: Going back to Charles Darwin, who waxed poetic on the wonders of barnacle dongs, biologists have trained their lens on the penis while remaining largely uninterested in what vaginas were doing. Yet penises don’t evolve in a vacuum. All those traits we ooh and aah over—length, girth, bristles—are shaped by vaginal evolution, and the mutual dance between the two that plays out over generations.

Now this is a straw insect. The reason why many species of insects (not just beetles) are identified by their penis shape is because that is the structure that is most likely to be clearly different between species. It’s not because biologists have an obsession with penises. In many Drosophila, for example, you can tell closely related species apart only by examining the male genitalia (even dissecting the female ones show no difference). As all entomologists know, “if there is only one trait differentiating closely related species, it is almost surely the shape of the male genitalia or genital apparatus.”

Now the reason for this probably reflects the action of sexual selection during the origin of new species, just as in many species of birds it is the male ornamentation and color and not the appearance of the female that is the most obvious species-distinguishing trait.

In insects, for example, the females of an isolated population may come, for reasons I won’t discuss, to prefer a slightly different genital shape in their mates, perhaps because it “feels better”. (We just don’t know the reason for this; I’m speculating here.) Eventually, because of this preference difference, you may get a snowballing difference in the shape of male genitals, and with it a big change in the female preference.

In the end, the two populations, via the action of sexual selection, come to differ from one another in both male genitalia and in female preference for the conspecific male genitalia—up to the point that females from one population will no longer mate with males from the other. We then have two reproductively isolated populations: new biological species.

Note that both sexes of the new species differ profoundly, but it’s dead easy to tell the species apart by the male genitalia, while it’s impossible to tell the species apart by looking at female genitalia. (Note: female genitalia may differ in some species, but to see that you’d have to do very elaborate dissections.)

You can tell the species apart by simply using a microscope to examine the male genitalia, but not the females. In fact, the females may differ in a way impossible to tell apart by looking at them, for their difference in preference may reflect how the different genitalia “feel” during copulation,  and “tactile feeling” is a preference impossible to see because it’s coded in the female’s neurons.

I’ve made this point repeatedly, most notably in my book Speciation with Allen Orr, and others have as well, especially William Eberhard in his unjustly neglected book Sexual Selection and Animal Genitalia. This concentration on male rather than female genitals does not reflect sexism at all: it reflects both the way that sexual selection works and the fact that the selection manifests itself as morphological differences between species in male but not in female genitalia.

(A side note: in groups like squid in which sperm is transferred not through a penis but through another organ, it is those organs that tend to differ among species. This again supports the idea that during speciation, male morphology changes but what changes in females is often neuronally-based “feeling preference”.)

The idea that female preference is unduly neglected because of the patriarchy is not a fair charge because nearly every theory of sexual selection involves a concomitant change in both male trait and female preference for that trait.  It is a hell of a lot easier to see trait differences than preference differences, which can be tested only by behavioral studies exposing females to males of different morphologies or of different species.

Author Rachel Gross emphasizes that it’s only the new activity of women scientists and LGBTQ scientists (!) that has led to an interest in female vaginal evolution. This simply isn’t true (well, it may be 2% true): many of the discoveries she emphasizes below were made by men, including the fascinating “pseudopenis” of the spotted hyena, repeatedly used as an example of a species whose females are “empowered” (another example of the Naturalistic Phallusy). The author says this:

Today, as more women and LGBTQ scientists enter the field, we’re finding that vaginas, far from passive tubes for ejaculate, are active organs that sort, store and reject sperm. Kangaroos have three vaginas (two for sperm reception, one for joey ejection); swallowtail butterflies see out of theirs; and duck vaginas spiral and curve in a penis-repelling labyrinth. Even for non-vagina-lovers, these facts help us understand how genitals evolve as a whole. Both are part of the same unified story—a much richer tapestry than just one body part can tell. Leaving one out, whichever one, blinds us to the fuller picture of sex and sexuality.

This is, I think, a gross distortion of the history of genital evolution. There’s more, and here her ideological lesson comes into view:

Both examples [JAC: the presence of multiple vaginas in kangaroos and “the neglect of guys in gynecology] reflect a deeper flaw in science’s approach to sex: the assumption that sex can only be either/or, two trains that run along separate, parallel tracks. Again and again, biology has proved this not to be the case—chromosomally, hormonally or genetically. For instance, we usually consider the presence of a penis to indicate a male, yet the hyena famously gives birth through her clitoris, which is so large that she can use it to mount the male. The female seahorse wields a long tube that looks an awful lot like a penis, which she uses to deposit eggs in the male’s pouch. So much for the penis as “the throbbing center of masculinity,” as Willingham puts it.

The lesson seems to be that sex is not binary IN HUMANS because of weird genitalic differences in other species. But sex is indeed binary in humans as defined biologically: males are the group that produce small, motile gametes (sperm) or have the potential to do so, while females are the group that produces large, immotile gametes (eggs) or have the potential to do so. THAT is the way, not penis shape or egg-delivering tubes, that biologists tell males from females, and the reason is because evolution forged sex that way: in animals, largely onto two tracks. The fact that a female seahorse deposits her eggs in the male’s pouch, and that he gestates the eggs and gives birth, says nothing about what obtains in humans, nor does it even say that “sex is not binary in seahorses.”  No, sex IS binary in seahorses:a male seahorse makes sperm and a female makes eggs.  What differs from most animals is which sex carries the fertilized eggs. But we’ve known that forever.

Finally, Gross gives us this message (my emphasis):

Here’s why: because human biases shape scientific knowledge, and much of what we know about our nether regions has been shaped by lazy, antiquated stereotypes about what men and women are. Looking past the penis and beyond the binary categories of male/female, penis/vagina (or, more accurately, penis/clitoris) opens our eyes to the full spectrum of gender and genitalia in all its glorious permutations. It makes for better science, and a deeper understanding of genital evolution and reproductive health.

Well, I’m not sure that Gross realizes that she’s given the game away by admitting flat out that yes, male/female is indeed a binary in humans.  Sex is binary. But yes, its manifestations, its twists and turns—like a duck’s penis—are fascinating to the biologist. Yet this does not mean either that the study of female genitalia have been of interest only to LGBTQ+ or female scientists, nor that we should draw any kind of lessons about how to best treat human males and females based on observing other species.

For another argument of the same stripe—that the diversity of nature tells us how patriarchal and sexist humans have been—see the article below from The Guardian. It, too, relies on a combination of anecdotes and the Naturalistic Phallusy, completely neglecting the great generalizations about the sexes first noted by Darwin. Once again the bonobos (who aren’t as nice as everyone thinks) are trotted out as an example of how females can be dominant in humans:

Ah yes, bonobos: these peaceable primates use sex toys, practise oral sex and establish and maintain female-led social structures through “genito-genital rubbing”. That’s entertaining, but it also matters: as Cooke says, it challenges the clichéd narrative on sex roles in primates, our closest animal relatives.

But why doesn’t the fact that the rest of the primate species show male aggression and “patriarchy” buttress the idea that males are the “dominant sex” in humans? Once again, it’s ludicrous to tell humans to right way to behave towards the sexes by pointing at other species. Nature is what it is, but human society, because of culture, can be made to abrogate what we see in nature—to circumvent evolution. The invention of contraception is one example.

As the biologist said who sent me the link below (a woman, by the way), “I suppose a more balanced account wouldn’t sell many books or warrant a big splash in a Sunday.”

(Lucy Cooke has a new book of “female myth-busting female-centered” stories,  Bitch: A Revolutionary Guide to Sex, Evolution & the Female Animal).

Taking a stand: Lucy Cooke by the giraffe enclosure at London Zoo. Photograph: Dan Burn-Forti/The Observer



Sexual versus natural selection: a case in beetles

October 4, 2021 • 11:15 am

Although Darwin himself drew a bit of a distinction between natural and sexual selection, the latter is really a special case of the former. Sexual selection is simply natural selection among individuals for their ability to acquire a mate: one of many behaviors that determine how many genes you leave behind. And there are cases in which it’s hard to determine which form of selection is going on. If a male’s sperm swim faster than the sperm of other males in a species where females are multiply inseminated (e.g., fruit flies), is that male experiencing positive natural selection or positive sexual selection?

Well, the details don’t matter so long as we keep track of what’s going on. In a new paper in Nature Communications, also summarized in a short News and Views in Current Biology, a group of investigators demonstrate how sexual selection can conflict with other forms of natural selection. The experiment was hard and laborious, but the results can be conveyed simply, and I’ll try.

I’d suggest that if you read one of the two articles, it should be the second, as it’s shorter, written for a less specialized audience, but nevertheless an accurate summary. But if you want the original paper, click on the screenshot below or get the pdf here.

To read the Current Biology precis, click on the screenshot below or get the pdf here. 

We begin with a sexually dimorphic beetle (below), Gnatocerus comutus, the “broad-horned flour beetle” that’s a pest in grain silos.  As you see, it’s sexually dimorphic, with males having bigger heads and, notably, a huge pair of mandibles (arrows). The females lack mandibles. That’s a hint that the mandibles aren’t used for defense against predators or for predation, but are used in male-male competition for females (if they helped procure prey or fight off predators, the females should have them, too). And indeed, that’s exactly what the mandibles are used for.


A prediction from this difference is that there is a metabolic cost to growing those mandibles, and although males with mandibles have higher overall fitness, if you could remove male-male competition, the mandibles wouldn’t give you a selective advantage. In that case they would be selected to evolve a smaller size as the resources used to grow them could be directed at other aspects of fitness. Every time you see a case of sexual dimorphism involving a cumbersome or conspicuous trait, you can predict that that trait has a cost, and is involved in sexual selection (the male peacock’s tail is the classic example).

The authors of the first paper did a clever experiment. Instead of removing male-male competition (you could do this by pairing one male with one female for generations; I predict the mandibles would get smaller), they exposed the males and females (separately) to a vicious predator, the assassin bug Amphibolus venator, which doesn’t regularly prey on G. comutus in nature but will eat anything it encounters.

Here’s the assassin bug confronting its potential prey (from the Current Biology paper):

What happened?

First, over 7 generations, with the males who escaped predation mated to control (unselected) females, the offspring of the escaping males evolved a smaller size. Clearly they weren’t defending themselves against predation from the assassin bugs; rather, the mandibles appear to have been an impediment to survival. The authors suggest that they’re heavy and impede the mobility you need to escape predators.

And, as expected, those small-jawed males whose descendants survived 7 generations of predation lost out when allowed to compete with regular males for females: they won contests only half as often as males from control treatments or female-only predation treatments. Jaws matter at mating time!

What was not expected was that the female descendants of the predated males actually got fitter.  Why? Because their abdomens got larger, possibly enabling them to produce more eggs. (An alternative is that females’ sperm storage organs got larger, enabling them to store more sperm.) But why would this happen? Probably because there is a genetic correlation between male mandible size and, in females, either abdomen or sperm-storage organ size, so if you make the former smaller, the latter get bigger. There’s independent evidence for this. (We don’t know about the developmental pathways that connect male jaws and female abdomens.)

What this shows is not only the cost of sexual selection, but a cost that’s levied in both males and females. If there were no male-male competition, and males had small mandibles, females would leave more offspring.  You might ask, then, given that there are of evolving mandibles paid by both sexes, why do males still evolve large jaws?

The answer must be that the genes that increased male mandible size in the past still had a NET advantage over genes for smaller mandibles. In other words, their cost in reduced ability to escape predators and reduced female offspring number was more than offset by the advantage of winning contests for females. This shows that fitness increases in one sex (the larger mandibles that evolved in males) can be paid for by fitness reductions in the other sex as well (reduced reproductive output of smaller-bellied females).

And so Nature has woven a tangled web here, but one somewhat untangled by the tedious but revealing experiments of the researchers who wrote the first paper.

A Pecksniffian anthropologist takes down Darwin for being a man of his time

May 22, 2021 • 11:30 am

It’s the 150th anniversary of the publication of Darwin’s The Descent of Man (people often forget that it’s paired with another book, Selection in Relation to Sex), and the journal Science has celebrated the year in two ways. The first is an article pointing out, tiresomely, erroneously, and not for the first time, that Darwin was a sexist, racist, colonialist, and oppressor whose theories supposedly harmed many people. That is the first note below (click on screenshot), written by Agustín Fuentes, a primatologist and biological anthropologist at Princeton University.

Click on the screenshot to read the piece:

The piece isn’t totally bad, but it’s bad enough that I want to register a few plaints. The main ones are that Fuentes is not saying anything that hasn’t been said before: Darwin indeed had some racist, sexist, colonialist, and white-supremacist views that were expressed in his works, especially in The Descent of Man (Fuentes repeatedly confuses the two books, as some of the views he criticizes appear in Selection in Relation to Sex).

To be fair, Fuentes does credit Darwin with his insight and his durable and correct theory of evolution. But as he gives with one hand, he takes with the other:

 But despite these ideal frames and some innovative inferences, “Descent” is often problematic, prejudiced, and injurious. Darwin thought he was relying on data, objectivity, and scientific thinking in describing human evolutionary outcomes. But for much of the book, he was not. “Descent,” like so many of the scientific tomes of Darwin’s day, offers a racist and sexist view of humanity.

Yes, the tired old Bucephalus of critical theory: “it’s problematic.”

And then we get the usual litany: Darwin believed that whites were superior to blacks and other non-Europeans; he thought women were inferior to men, opined that eventually the white “race” would supplant other groups, and so on. This much we’ve all known for a long time, and many of us, including me, have taught it to our students.

But, despite Fuentes’ admission of Darwin’s strong abolitionism, he seems to forget that Darwin was a man of his time, not of our time. Is it fair to judge Darwin against an enlightened modern liberal? I don’t think so: the proper judgment is to see whether Darwin was palpably morally worse than most other Victorian Englishmen.  And I don’t think he was. I’ll explain a bit more below, but I have a very hard time thinking of someone of Darwin’s stature in Europe who was much better than he on the issue of women, or, for that matter, slavery. (Read Marx and Engels on the Irish if you want real bigotry.) Yes, Darwin saw some South Americans as “savages”, but he also perceived their common humanity with us, and his theory affirmed our common ancestry. And yes, he saw women as the inferior sex; but how many Victorian men were far more enlightened than he?

Frankly, I’m tired of people who say things like “Darwin was bad because he should have known and done better.” Neither he nor his contemporaries did or could have: morality evolves, and in 150 years our own generation may be seen as just as morally deficient as was Darwin. After all, we eat meat, and in the future we may learn more about the suffering of animals in ways that would brand us moderns as horrible barbarians. The judgment of celebrating Darwin should rest on a). “is he being celebrated for the good things he did?” (answer: yes), and b). “did the good he did in his life outweigh the bad?” (answer: also yes).

Now, onto what I see as Fuentes’s missteps. Here’s one about selection and racial differentiation:

Darwin portrayed Indigenous peoples of the Americas and Australia as less than Europeans in capacity and behavior. Peoples of the African continent were consistently referred to as cognitively depauperate, less capable, and of a lower rank than other races. These assertions are confounding because in “Descent” Darwin offered refutation of natural selection as the process differentiating races, noting that traits used to characterize them appeared nonfunctional relative to capacity for success. As a scientist this should have given him pause, yet he still, baselessly, asserted evolutionary differences between races.

. . . His adamant assertions about the centrality of male agency and the passivity of the female in evolutionary processes, for humans and across the animal world, resonate with both Victorian and contemporary misogyny.

The first part of this is fine, but the second, about how “races” and sexes come to differ from one another morphologically, is not. Darwin saw sexual selection (a subset of natural selection, by the way) as the process whereby different ethnic groups come to differ in appearance. He may well have been right about this. And clearly, there are evolutionary differences between the appearance of ethnic groups. These are certainly genetic, and the morphological homogeneity within groups compared to the palpable differences between groups suggest an evolutionary origin.

What kind of evolution was it? As I said, Darwin’s view was that groups of humans (as well as males versus females) are affected by sexual selection based on either male-male competition or “choice”. The choice, according to Darwin, was made by females preferring arbitrary but aesthetically appealing male traits: song, ornaments, plumage, and so on. (For humans, Darwin sometimes intimated that the “choice” was made by males, but by females in other animal species.) This “beauty matters” hypothesis has its biggest exponent in Richard Prum, and though I am not convinced by his arguments, it’s mainly because we lack data, not because Prum is known to be wrong. Here’s Prum in a paper discussing Darwin’s views:

Darwin was explicit, repeated and adamant in maintaining that the evolution of secondary sexual characters by mate choice was an aesthetic mechanism of evolution. For example, he wrote:

With the great majority of animals, however, the taste for the beautiful is confined to the attractions of the opposite sex.* The sweet strains poured forth by many male birds during the season of love, are certainly admired by the females … If female birds had been incapable of appreciating the beautiful colours, the ornaments, and voices of their male partners, all the labour and anxiety by the latter in displaying their charms before the females would have been thrown away; and this is impossible to admit. [, p. 61]; * sentence added in second edition)

On the whole, birds appear to be the most aesthetic of all animals, excepting of course man, and they have nearly the same taste for the beautiful as we have. [, p. 466]

[Male birds] charm the female by vocal and instrumental music of the most varied kinds. [, p. 466]

It is important to establish what Darwin’s language meant in modern terms. Darwin lacked our modern sensitivity to avoiding anthropomorphizing his subjects. Rather, he was actively engaged in reducing the distinctions between humans and animals. But Darwin was not trying to shock his readers. He used these aesthetic terms as ordinary language without any special semantic or cultural implications. Darwin was specifically proposing that animals (mostly females) were making sensory and cognitive evaluations of display traits, and making mate choices based on those evaluations. Darwin used ‘taste for the beautiful’ to refer to differential behavioural response to a secondary sexual sensory stimulus. While this aspect of Darwin’s opinion was highly controversial at the time [], it is mainstream now. If that were the only issue, there would be no need for us to revive Darwin’s use of aesthetic language. Our contemporary terms cover this meaning.

While I doubt Prum’s views as a general explanation of sexual dimorphism (I’m more inclined to see differences between human ethnic groups as a “beauty matters” issue), he may be right in some cases, and at any rate note that the agency here is exercised by females, not males. In what sense, then, are Fuentes’s females “passive” if they are choosing among males competing for their attentions? Darwin makes the females quite active!

Speaking of stuff that Darwin got wrong, his biggest whopper was his erroneous theory of genetics, in which he thought that hereditary “mutations” were invoked by environmental change, a “Lamarckian” view. We know now that Darwin was wrong, but fortunately his theory didn’t depend on a correct mechanism of genetics, but only on the fact that there was genetic variation in populations that could be passed on, and affected survival and reproduction. The fact that Fuentes omits this biggest whopper in favor of moral indictments shows that he has an explicitly ideological aim, which he reveals in the last paragraph of his article (see below).

Here’s a Fuentes whopper about “survival of the fittest,” a term that Darwin didn’t invent and generally avoided, using it only a handful of times in his writings:

[Darwin] went beyond simple racial rankings, offering justification of empire and colonialism, and genocide, through “survival of the fittest.” This too is confounding given Darwin’s robust stance against slavery.

This is wrong on two counts. First, Darwin never justified genocide, though he did think that by virtue of (inherited) superiority, the white race would come to dominate others by higher relative success. But never did he advocate the killing or extirpation of different ethnic groups. Second, the use of “social Darwinism” by others to justify such mistreatment of other groups was always rejected by Darwin. Darwin simply cannot be blamed for the misuse or misconstrual of his theory by others. In fact, I cannot think of what direct harm Darwin really caused to anyone, save his buttressing the views of English men and women of his time. I always maintain that if Darwin lived today, he would likely decry misogyny, racism, and white supremacy, and would be a liberal English guy. It’s unfair, again, to tar him for adhering to the moral standards of his time—indeed, in having higher standards.

Finally, Fuentes neglects that Darwin did do some backsliding about the hegemony of natural selection as an explanation for everything. Here’s a quote from The Descent of Man: (h/t Nick Matzke)

. . . . but I now admit, after reading the essay by Nägeli on plants, and the remarks by various authors with respect to animals, more especially those recently made by Professor Broca, that in the earlier editions of my ‘Origin of Species’ I probably attributed too much to the action of natural selection or the survival of the fittest. I have altered the fifth edition of the Origin so as to confine my remarks to adaptive changes of structure. I had not formerly sufficiently considered the existence of many structures which appear to be, as far as we can judge, neither beneficial nor injurious; and this I believe to be one of the greatest oversights as yet detected in my work. I may be permitted to say as some excuse, that I had two distinct objects in view, firstly, to shew that species had not been separately created, and secondly, that natural selection had been the chief agent of change, though largely aided by the inherited effects of habit, and slightly by the direct action of the surrounding conditions. Nevertheless I was not able to annul the influence of my former belief, then widely prevalent, that each species had been purposely created; and this led to my tacitly assuming that every detail of structure, excepting rudiments, was of some special, though unrecognised, service. Any one with this assumption in his mind would naturally extend the action of natural selection, either during past or present times, too far.

Yes, Darwin went back and altered the fifth edition of The Origin to reflect this change of views.

In Fuentes’s last paragraph, he reveals his aim: to increase inclusion and diversity (presumably racial and gender diversity) among evolutionists in hope that this will it easier to catch Darwin’s moral errors as well as those of other evolutionary biologists.


Reflecting on “Descent” today one can look to data demonstrating unequivocally that race is not a valid description of human biological variation, that there is no biological coherence to “male” and “female” brains or any simplicity in biological patterns related to gender and sex, and that “survival of the fittest” does not accurately represent the dynamics of evolutionary processes. The scientific community can reject the legacy of bias and harm in the evolutionary sciences by recognizing, and acting on, the need for diverse voices and making inclusive practices central to evolutionary inquiry. In the end, learning from “Descent” illuminates the highest and most interesting problem for human evolutionary studies today: moving toward an evolutionary science of humans instead of “man.”

Re the first part: yes, scientists have long rejected the simplistic view of “races” as easily demarcated groups of people that differ genetically in profound ways, but we still recognize clustered ethnic groupings. As for “no biological coherence to male and female brains”, I believe that this is a matter of debate (see here) and, at any rate, I do believe that evolution has differentiated male and female brains in terms of the tendencies it has given the sexes to behave differently or possess different preferences (there is of course considerable overlap). One example is the male-female difference in sexual behavior, similar to that of many other animals.  This must be coded somehow in the brain. As far as “survival of the fittest” not accurately representing the dynamics of the evolutionary process, well, duhhh. For 30 years I’ve told my classes that “reproduction of the fittER” is a more accurate characterization of how natural selection works, and an even more accurate representation would be that “the genes that become more numerous over evolutionary time are those that leave more copies of themselves.” The latter idea is hard to convey to undergraduates, though!

While I do believe that some of our unrecognized prejudices can be addressed by broadening the types of people we want to attract to evolutionary biology (I think the emphasis on female preference in sexual selection was promoted to some extent by women biologists), I really don’t think that making diversity and inclusion the central focus of “evolutionary inquiry” will lead to profound breakthroughs. This presumes that there are race- or gender-based ways of thinking about evolution, and while this may be true to some extent, I don’t think it’s true to an appreciable or important extent. What we need is to start turning on kids to evolution at a young age; that is, we should “widen the pipeline”, attracting the best thinkers from all groups. It is deeply patronizing to try to hire minorities so they can help us “reject the legacy of of bias and harm in the evolutionary sciences.”

To counterbalance the tut-tutting of Fuentes, though, we have a longer article in the same issue which talks about Darwin’s book, shows its contributions, and steers well clear of morality. Click on screenshot to read the article:

And its summary:

Charles Darwin’s The Descent of Man was published in 1871. Ever since, it has been the foundation stone of human evolutionary studies. Richerson et al. reviewed how modern studies of human biological and cultural evolution reflect the ideas in Darwin’s work. They emphasize how cooperation, social learning, and cumulative culture in the ancestors of modern humans were key to our evolution and were enhanced during the environmental upheavals of the Pleistocene. The evolutionary perspective has come to permeate not just human biology but also the social sciences, vindicating Darwin’s insights.

The ideology and the “I’m better than Darwin was” attitude can be left for classes in the history and philosophy of science.


h/t: Nick Matzke, Andrew Berry, Brian Charlesworth, and Matthew Cobb for discussion.

Octopus sex

March 19, 2021 • 2:30 pm

Let’s end the work week with some animal behavior: in this case, octopus sex. I don’t even know how a male octopus determines that another individual is female!

The narration is pretty twee, but if the males really compete to see who has the bigger suckers, that would be fascinating.  And the arm that delivers sperm is pretty cool.

I wish the video were a bit more informative about biology, for even ZeFrank, funny as he is, has more useful information than does this National Geographic production, which seems dumbed down.

Reader’s wildlife video

March 15, 2021 • 8:00 am

When it rains it pours: Tara Tanaka has graced us with another video, this time with the mating display of a male great egret (Ardea alba), the formation of a pair bond, and the beginnings of a nest. It is so beautiful that it made me tear up. And the male bringing sticks for the nest is fantastic. Be sure to watch this on the big screen.

Her video notes:

This is the closest Great Egret nest site in our backyard wildlife sanctuary – approximately 250’ away. There hasn’t been a nest here is a couple of years due to low water, but the afternoon before last I saw a male displaying on a branch, and the next morning he had already attracted a mate. He repeatedly brought branches from across the pond, and with sometimes questionable hand-offs she skillfully wove the sticks into their growing nest.

Tara’s Vimeo site is here, and her Flickr site is here.

Faux Duck o’ the Week

November 30, 2020 • 8:00 am

I completely forgot about Sunday’s Faux Duck O’ the Week, being occupied yesterday with The Auction and all. But better late than never, and here’s the latest in biologist John Avise‘s series of waterfowl that resemble ducks but aren’t. Can you guess this species?

His captions and Fun Duck Facts are indented. (To see the ID, Fun Duck Facts, and range map, go below the fold.)

At its summer home in Central Alaska:

Close-up in breeding plumage:

Frontal view:


With next week’s species to its left:

Click on “read more” for the identification, John’s Fun Faux Duck facts, and a range map: Continue reading “Faux Duck o’ the Week”

The woodies are changing!

October 5, 2020 • 2:00 pm

The two male wood ducks (Aix sponsa) in Botany Pond are still here, though the Lady Woodie flew the coop. And the two males, who get plenty of noms from us, are starting to change their plumage from the non-breeding form to the fantastic breeding coloration.

Here are the woodies on September 16. This first one is a male:

In the photo below, the one on the right with the pink beak is a male, while the one on the left, with the gray beak, is the female, now departed. The creature in the rear is not a duck.

Here are the two males today. Their heads are turning iridescent green, their wings blue, their beaks red, and they’re getting a lovely stippled chest pattern, as well as their cherry red eyes:

Head starting to green up. For the endpoint, see the last photo:

The pair of males, who are named Frisky and Blockhead, like to perch on the knees of the cypress tree. After all, they’re perching ducks and like to have wood under their feet. I like to think they’re brothers. They’re nice and plump, too, as we feed them well.

If we keep them around for another short while, they should wind up looking like this (picture from Wikipedia). Ah, the marvels of sexual selection and development! I really want to see this happen:

Oh, and Honey is still around, continually asserting her alpha-female status by attacking other mallards at feeding time.