An evolutionary biologist lists and discusses the ten most influential books in the field

April 7, 2026 • 11:00 am

I would have missed this video had reader Doug not called my attention to it. It’s a very good half-hour discussion by evolutionary biologist Zach B. Hancock, a professor at Augusta University, in which he recommends the the top ten most influential books in evolutionary biology. Since Hancock is a population geneticist, the books deal largely with evolutionary genetics, but not all of them.

I slipped in at #10 with my book on Speciation with Allen Orr, but I won’t be too humble to claim our book wasn’t influential, for, as Hancock notes, it’s the only comprehensive book on the origin of species around. (Darwin’s big 1859 book was about the origin of adaptations, and had little that was useful about the origin of species.) Hancock regrets that Allen and I aren’t going to do a second edition, but Allen refuses to, and I don’t have the spoons (I do have 200 pages of notes on relevant papers that appeared after our book came out, but that will go nowhere.)

The rest of the list is stellar, and shows a keen judgement about the field. I’m not sure I would have put Lack’s book on the Galápagos finches in there, as it’s pretty much out of date. It should be replaced by a very important book by Ernst Mayr, his Systematics and the Origin of Species or the updated version in 1963,  Animal Species and Evolution. It was Mayr who codified the Biological Species Concept and paved the way for experimental and observational studies of speciation, and hence my book with Orr. 

I’d expect every graduate student in evolutionary genetics to have read  most of these books by the time they get their Ph.D. In fact, when I was on prelim hearings, judging whether students could be admitted to candidacy after a year or two, I and my colleague Doug Schemske made a habit of asking students to name the major accomplishments of several of the authors listed below. My impression is that the history of the field is not given so much weight now, so I wonder if students could still explain the major accomplishments of say, Theodosius Dobzhansky or Ronald Fisher. The books are of more than historical interest, for they raise questions that are still relevant. (I spent a lot of my career trying to understand the phenomenon of “Haldane’s Rule,” explained by J.B.S. Haldane in 1922. The paper was completely neglected until I read it in the early eighties and started a cottage industry of explanations [my own was largely wrong]).

Hancock’s explication of each book is excellent.  If you’re an academic teaching evolutionary biology, you might see how many of these books your students have read.

One commenter on YouTube gave the list and the time points in the video where each is discussed (the links go to those time point).

2:26 #10 Speciation – Jerry Coyne & Allen Orr
4:50 #9 Darwin’s Finches – David Lack
6:59#8 Evolution: The Modern Synthesis – Julian Huxley
9:15 #7 The Origins Of Genome Architecture – Michael Lynch
11:23 #6 Chance & Necessity – Jacques Monod
13:26 #5 The Selfish Gene – Richard Dawkins
16:54 #4 The Neutral Theory of Molecular Evolution – Motoo Kimura
19:34 #3 Genetics and the Origin of Species – Theodosius Dobzhansky
22:20 #2 The Genetical Theory Of Natural Selection – Ronald Fisher
26:35 #1 On The Origin Of Species – Charles Darwin

Two “Times” obituaries for Robert Trivers

April 7, 2026 • 9:45 am

Reader Simon called my attention to a new obituary in the Times of London of Robert Trivers, a giant in evolutionary biology (and a notorious eccentric) who died on March 12.  Because his death wasn’t announced immediately after he expired, this was bit late, but better late than never—especially given Trivers’s importance in the field. It’s a good obituary but the gold standard was Steve Pinker’s “in memoriam” article about Trivers published in Quillette on March 25.

Click the screenshot below to read, and if that doesn’t work,the article is archived here.

An excerpt:

In a burst of creativity in the early 1970s, Robert Trivers published a series of scientific papers that earned him a claim to being among the most important evolutionary theorists since Darwin. He was the first to fully appreciate how a gene-centric view of natural selection could explain some of the most puzzling and fundamental patterns in social life: the function of altruism, why males and females differ so much, the underpinnings of sibling rivalry and the delicate dynamic of conflict and co-operation that exists between parent and child.

Brilliantly original, Trivers was also an academic misfit: a foul-mouthed, pot-smoking individualist with a notable tendency to get into violent scrapes and an ungovernable character that eventually strained his relationship with the academy to breaking point.

Why do we ever behave altruistically? That is, why would an organism ever promote the reproductive success of another at some cost to its own? Since the work of the great evolutionist WD Hamilton, it had been appreciated that “kin selection” could explain why close relatives help one another out: doing so promotes an organism’s “inclusive fitness”, a measure accounting not only for an organism’s own genes but for copies of the same genes likely to be present in relatives. But why help non-kin? To Trivers, it was an obvious fact of life that we sometimes give priority to friends, and even strangers, over direct relatives.

Persuaded of the misguidedness of “group selectionist” theories that were fashionable at the time — according to which organisms sometimes sacrifice themselves for the “good of the species” — Trivers gave the central explanatory role to the gene. In his landmark 1971 paper, The Evolution of Reciprocal Altruism, Trivers argued that altruism depended on the possibility of reciprocity. As long as helping a non-relative is not too costly, and there is sufficient probability that the favour would one day be returned, genes coding for altruistic dispositions spread.

. . . Frustrated by the Harvard biology faculty’s delay in granting his tenure application in the late 1970s, he abruptly left with his young family to take up a position at the University of California, Santa Cruz, a decision he came to regard as a “once in a lifetime” mistake. There, he befriended Huey Newton, co-founder of the paramilitary Black Panther political party, who was a doctoral student at the university. They co-authored a paper on self-deception, and Trivers made Newton his daughter’s godfather. He joined the Panthers for a period and later confessed to doing “an illegal thing or two”, before Newton removed him from the group for his own safety.

In fact, what I recall in 1977 is that Harvard’s biology department recommended tenure for Trivers, but that recommendation was overturned by President Derek Bok.  I was there at the time and can vouch for that. Others say that Trivers asked for early tenure and was denied that, and then decided to leave Harvard. I also heard, and I can’t vouch for this, that Richard Lewontin (my Ph.D. advisor) and Dick Levins, both Marxists who despised sociobiology, went to President Bok to lobby him to deny Trivers tenure.  What we do know is that Trivers then moved to Santa Cruz, and later to Rutgers, where his academic turmoil continued:

. . . In 2015 he was suspended by Rutgers University for refusing to teach a course on human aggression, a field he claimed he was not expert in (despite its being a personal forte of his). He quit university life for good shortly after. Later, he was among the set of high-profile intellectuals pilloried for maintaining financial and social links to Jeffrey Epstein, even after the latter’s conviction for sex offences. Far from apologetic, Trivers, who accepted funding from Epstein to study the relationship between knee symmetry and sprinting ability, vouched for his integrity; in Trivers’s view, Epstein’s imprisonment was punishment enough and his crimes less “heinous” than they were made out to be.

It is testament to the depth and generality of Trivers’s discoveries that they could be applied so readily, as he unsparingly conceded, to his own case. As he understood, natural selection has built us, and it is to natural selection we must return “to understand the many roots of our suffering”.

Compared to Pinker’s piece, the Times obituary is light on Trivers’s scientific accomplishments, but all in all it’s pretty good.

Below is a NYT obituary, also delayed, that appeared on March 27 (click to read or find it archived here):

An excerpt (David Haig, who’s quoted, has written his own remembrance of Trivers, as the two were good friends; but I don’t think it’s yet been published):

“Robert Trivers was unlike any other academic I have known,” David A. Haig, an evolutionary biologist at Harvard, wrote in a remembrance of Professor Trivers for the journal Evolution and Human Behavior. “In another life, he might have been a hoodlum.”

Raised by a diplomat and a poet, and educated at Phillips Academy in Andover, Mass., and Harvard University, Professor Trivers thrived on challenging scientific orthodoxies, calling the field of psychology a “set of competing guesses.” (He also scorned physics, noting that its utility was “connected primarily to warfare.”)

In the early 1970s, as a graduate student at Harvard and later as an untenured professor there, he published a series of papers applying Darwin’s theory of natural selection to social behavior, arguing that science had failed to connect evolution to an understanding of everyday life.

“I was an intellectual opportunist,” he wrote in “Natural Selection and Social Theory: Selected Papers of Robert Trivers” (2002). “The inability of biologists to think clearly on matters of social behavior and evolution for over a hundred years had left a series of important problems untackled.”

The paper does a decent job in outlining Trivers’s contributions, the most important of which was his evolutionary explanation of “reciprocal altruism”, but again, see Pinker for a fuller explication.  A bit more about the situation at Harvard:

During this creative burst, Professor Trivers struggled with mental health issues and was hospitalized at least once for bipolar disorder. He applied for early tenure at Harvard, but the decision was postponed because of concerns about his mental health.

“He could be a brilliant and wonderful colleague,” Professor Haig said. “In a different mood, he could be unnecessarily hostile to those around him.”

That’s enough for now, save one I just found in Skeptic, a remembrance by Trivers’s only graduate student ever, Robert Lynch. Click below to read:

It ends this way:

One of the last times I spoke with Robert, a fall had left his right arm nearly useless. He described it as “two sausages connected by an elbow.” He was a chaotic and deeply imperfect man, but also one of the few people whose ideas permanently changed how we understand evolution, animal behavior, and ourselves. Steven Pinker wrote that “it would not be too much of an exaggeration to say that [Trivers] provided a scientific explanation for the human condition: the intricately complicated and endlessly fascinating relationships that bind us to one another.”  That seems just about right to me.

His ideas are some of the deepest insights we have into human nature, animal behavior, and our place in the web of life. The mark of a great person is someone who never reminds us of anyone else. I have never known anyone like him.

I’ll miss you, Robert. You asshole.

A transitional fauna shows that the “Cambrian explosion” was happening before the Cambrian

April 5, 2026 • 8:30 am

The Cambrian Period, beginning at 538.8 Ma (million years ago) and lasting about 52 million years, is famous for marking the transition from simple and largely unicellular animals to, beginning at the period’s inception, representatives of modern groups.  This apparently rapid onset of modern forms of multicellular animals constitutes the famous “Cambrian Explosion.”

The Cambrian was preceded by the 96-million-year-long Ediacaran period, extending from 635 million years ago to the beginning of the Cambrian. The Ediacaran fauna, consisting of some multicellular animals of unknown affinity and things looking like members of some modern groups like cnidarians (represented today by jellyfish, corals and anemone). But most of the Ediacaran groups appeared to have died out at the end of the Ediacaran, and for unknown reasons.

The boundary between the Ediacran and the Cambrian thus marks a major transition in animal life.   Many of the “modern” groups that first arose during the Cambrian don’t have apparent ancestors in the Ediacaran, and so those modern groups were thought to have evolved almost instantaneously (in geological time!). But surely modern groups had ancestors during the Ediacaran: unless you’re a Biblical fundamentalist, you realize that ancestors of modern groups had to have existed well before the Cambrian explosion.

Now a paper in Science, based on a fossil group called the Jiangchuan Biota that spans the period from 559-534 million years ago, shows that representatives of “modern” groups seen in the Cambrian explosion were indeed present in the late Ediacaran, pushing back the time of origin of modern phyla 4-5 million years.  This conclusion was possible because of the remarkable preservation of the animals (and some algae), all present as carbonaceous films on rocks—the same kind of films (presumably due to rapid burial) that enabled us to see the remarkable Burgess Shale fauna of the middle Cambrian. The new find was in the province of Yunnan in Southwestern China.

You can see the paper by clicking the screenshot below, reading the pdf here, or reading the shorter blurb at an Oxford University sit. at the bottom. All photos below are taken from the paper.

I won’t go into all the terminology involved in identifying the groups but will show a few fossils from the paper strongly suggesting that some “modern” groups arose in the late Ediacaran.

First, an anomalous animal that appears to be some kind of worm, but one with a “holdfast” disc on its butt. We don’t know what this one is, but it has oral projections or tentacles. The disc is very clear:

Another wormlike animal (note that these are small: a few millimeters) having a clear oral region. Again, we’re not sure what this is, but the preservation as a carbon film is remarkable:

A deuterostome (animals where the first opening in the embryo becomes the anus rather than the mouth), a group thought to have appeared in the Cambrian but here seen in the Ediacaran: this one resembles  Herpetogaster, known from the early Cambrian which, according to Wikipedia, “possessed a pair of branching tentacles and a tough but flexible body that curved helically to the right like a ram’s horn and was divided into at least 13 segments”. This one, like Herpetogaster, has tentacles (at leat four) and a stalk.  It’s interpreted as a relative of acorn worms, relatives of modern echinoderms which are hemichordates, the closest living group to modern chordates (animals with notochords and a dorsal nerve chord, which include all vertebrates).

The one below,described in the paper as “Margaretia-like animal now known as a dwelling tube for an enteropneust hemichordate worm”. It’s also described as having “regular, oval-shaped holes running along its length”. Again, we see what is likely an early hemichordate, showing that the relatives of modern chordates seem to have been present several million years before the Cambrian explosion began.

The one below is identified as a ctenophore, or comb jelly, a phylum of early animals previously known only from the mid-Cambrian. “OS” stands for “oral skirt”, described as “a specialized, often scalloped, muscular, or rigid structure surrounding the mouth, primarily found in Cambrian-era fossil comb jellies such as Ctenorhabdotus and Thalassostaphylos. Unlike modern ctenophores, these ancient species used the skirt for feeding, potentially to engulf large prey.”

Finally, this animal is thought to be an early cnidarian with tentacles and a holdfast (HF). Although one form identified as a cnidarian had already been recognized from the Ediacaran, here we have another that’s different, showing a radiation of cnidarians before the Cambrian.

These fossil data support already-existing molecular data suggesting that animal groups had already evolved and diversified before the Cambrian, though until now no fossils, or only a few suggestive fossils, were known.

The authors’ summary below, though written in scient-ese, basically says that a major radiation of animal phyla had already begun before the Ediacran/Cambrian boundary, but we did not know about it because the conditions for forming this kind of trace fossil, requiring rapid burial in marine sediment (and subsequent finding by investigators!) were infrequent:

The new Jiangchuan animal fossils, dominated by bilaterians of apparently diverse affinities, with rarer fossils more typical of late Ediacaran deposits, could be described as a “Cambrian-type” assemblage from the late Ediacaran. A dominantly bilaterian assemblage from the late Ediacaran may not have been discovered until now as a result of the paucity of carbonaceous compressions from this time, hinting at a broader taphonomic bias (51).

If you want a short, readable summary of the importance of this fine, click below to read a shorter summary from Oxford University.

Two obituaries of Robert Trivers

March 25, 2026 • 9:30 am

Although I did call attention to the death of Robert Trivers, age 83, on March 12, and I knew him slightly, I did not have the chops to summarize his many contributions, nor did I know him that well (we overlapped at Harvard). Fortunately, Steve Pinker has produced an absolutely terrific bio of Trivers at Quillette: a piece that summarizes the many contributions to evolutionary biology made as a young man, and then his many eccentricities, quirks and obnoxious or even illegal behaviors that made Trivers somewhat of an apostate. He was a complex and fascinating person, and I hope someone will write his biography (he did write an autobiography, Wild Life: Adventures of an Evolutioanry Biologist, but deserves a thorough, disinterested, and Cobb-like treatment).

Steve’s obituary, which you can access by clicking on the screenshot below or seeing it archived here, is roughly in three sections: Trivers’s contributions to the field, an analysis of why they came so young and so fast (he did almost nothing during the last five decades of his life), and a description of his complex personality and behavior. It’s long for an obituary, but Trivers deserves long, and of course Pinker summarizes his life eloquently.

Trivers’s major contributions as Steve outlines them (Steve’s words are indented, bold headings are mine):

. . . two weeks after the death of Robert Trivers, one of the greatest evolutionary biologists since Charles Darwin, not a single major news source has noticed his passing. This despite Trivers’s singular accomplishment of showing how the endlessly fascinating complexities of human relations are grounded in the wellsprings of complex life. And despite the fact that the man’s life was itself an object of fascination. Trivers was no ordinary academic. He was privileged in upbringing but louche in lifestyle, personally endearing but at times obstreperous and irresponsible, otherworldly brilliant but forehead-slappingly foolish.

I still can’t see an obituary for Trivers in either the NYT or the Washington Post. That lacuna is shameful. On to his contributions (

Contributions:

Parent-offspring conflict:

Trivers’s innovation was to show how the partial overlap of genetic interests between individuals should put them in a partial conflict of psychological interest. The key resource is parental investment: the time, energy, and risk devoted to the fitness of a child. Parents have to apportion their investment across all their children, each equally valuable (all else the same). But although parents share half their genes with each child, the child shares all its genes with itself, so its interest in its own welfare will exceed that of its parents. What the parent tacitly wants—half for Jack, half for Jill—is not what Jack and Jill each want: two thirds for the self, one third for the sib. Trivers called the predicamentparent-offspring conflict.

Sex differences in parental investment:

Trivers explained the contrast by noting that in most species the minimal parental investments of males and females differ. Males can get away with a few seconds of copulation; females are on the hook for metabolically expensive egg-laying or pregnancy, and in mammals for years of nursing. The difference translates into differences in their ultimate evolutionary interests: males, but not females, can multiply their reproductive output with multiple partners. Darwin’s contrast can then be explained by simple market forces. And in species where the males invest more than the minimum (by feeding, protecting, or teaching their offspring), males are more vulnerable than females to infidelity (since they may be investing in another male’s child) and females are more vulnerable to desertion (since they may bear the costs of rearing their mutual offspring alone).

Reciprocal altruism:

In another landmark, Trivers turned to relations among people who are not bound by blood. No one doubts that humans, more than any other species, make sacrifices for nonrelatives. But Trivers recoiled from the romantic notion that people are by nature indiscriminately communal and generous. It’s not true to life, nor is it expected: in evolution as in baseball, nice guys finish last. Instead, he noted, nature provides opportunities for a more discerning form of altruism in the positive-sum exchange of benefits. One animal can help another by grooming, feeding, protecting, or backing him, and is helped in turn when the needs reverse. Everybody wins.

Trivers called it reciprocal altruism, and noted that it can evolve only in a narrow envelope of circumstances.

This to me is Trivers’s most important contribution, explaining not only why we sacrifice for unrelated people, but also making testable (and largely verified) predictions about human behavior, including morality.  Now that humans no longer live in small groups of acquainted people—conditions under which reciprocal altruism presumably evolved—we can expect some of those behaviors to disappear, but civilization is a mere eyeblink compared to the long, long period in which the conditions were right for the evolution of altruism (and deceit; see below).

Asymmetries in human relationships:

. . . in a passage that even fewer readers noticed, Trivers anticipated a major phenomenon later studied in the guise of “partner choice.” Though it pays both sides in a reciprocal partnership to trade favours as long as each one gains more than he loses, people differ in how much advantage they’ll try to squeeze out of an exchange while leaving it just profitable enough for the partner that he won’t walk away. That’s why not everyone evolves into a rapacious scalper: potential partners can shun them, preferring to deal with someone who offers more generous terms. Just as a store with a reputation for fair prices and good service can attract a loyal clientele and earn a bigger profit in the long run than a store that tries to wring every cent out of its customers only to drive them away, a person who is inherently generous can be a more attractive friend, ally, or teammate than one who dribbles out favours only to the extent he expects them to be repaid with a bonus. The advantage in attracting good partners makes up for the disadvantage in forgoing the biggest profit in each transaction.

And since humans are language users—indeed, reciprocity may be a big reason language evolved—any tendency of an individual to reciprocate or cheat, lavish or stint, does not have to be witnessed firsthand but can be passed through the grapevine. This leads to an interest in the reputation of others, and a concern with one’s own reputation.

The evolutionary significance of deceit and self-deception:

Trivers’s fifth blockbuster was laid out not in an academic paper but in a pair of sentences in his foreword to The Selfish Gene:

If (as Dawkins argues) deceit is fundamental to animal communication, then there must be strong selection to spot deception and this ought, in turn, to select for a degree of self-deception, rendering some facts and motives unconscious so as not to betray—by the subtle signs of self-knowledge—the deception being practiced. Thus, the conventional view that natural selection favors nervous systems which produce ever more accurate images of the world must be a very naïve view of mental evolution.

We lie to ourselves the better to lie to others, protecting compromising private knowledge from emotional tells or factual contradictions (as in the Yiddish saying, “A liar must have a good memory.”) In his book Social Evolution(1985), Trivers muses on how this can play out:

Consider an argument between two closely bound people, say, husband and wife. Both parties believe that one is an altruist of long standing, relatively pure in motive, and much abused, while the other is characterized by a pattern of selfishness spread over hundreds of incidents. They only disagree over who is altruistic and who selfish.

The theory of self-deception is deeper (and more enigmatic) than the commonplace that people’s views of themselves are mistuned in their favour. The self, Trivers implied, is divided: one part, seamless with the rest of consciousness, mounts a self-serving PR campaign; another, unconscious but objective, prevents the person from getting dangerously out of touch with reality.

Trivers wrote an entire book about this, a book that he intended to co-author with the (in)famous Huey Newton, a founder of the Black Panthers (Newton was murdered before it could be written): The Folly of Fools: the Logic of Deceit and Self-Deception in Human Life. It’s an uneven book, larded with bizarre personal anecdotes, but it also contains a lot of intriguing food for thought. In other words, it’s pure Trivers.

Why did Trivers make these contributions?  A few of Steve’s thoughts:

. . . Trivers revelled in explaining the contradictions of the human condition, and he himself was a mess of them. Foremost is how he revolutionised the human sciences in a fusillade of ideas he had between the ages of 28 and 33 (I didn’t even mention a sixth one, on how parents should invest in sons versus daughters). But then he did nothing comparable for fifty years. He wrote some good books, but they were reviews of his and others’ contributions, breaking little new ground. How do we explain this shooting star?

Part of the answer is that, as with all intellectual revolutions, the right mind found itself in the right era. In 1971 the gene’s-eye view of evolution was new and counterintuitive, as it remains to this day. People, including scientists, project their moral and political convictions onto the things they study, and the ideal that we should love our neighbours, act for the good of the group, and strive for social betterment is easy to read into nature, even if it flouts the logic of natural selection. And whenever the word “gene” comes up, readers get distracted by hallucinations such as that humans are robots controlled by their genes, that each of their traits is determined by a single gene, that they may be morally excused for selfishness, that they try to have as many babies as possible, that they are impervious to culture, and other non sequiturs.

The young Trivers, mentored at Harvard by the biologists William Drury and Ernst Mayr, immediately grasped the new way of looking at evolution, and never got hung up by these misconceptions. A jaundiced view of animals, not excluding Homo sapiens, came naturally to his rebellious temperament, and many puzzles he observed in his field work (including on ants, lizards, gulls, songbirds, caribou, baboons, and chimps) fell into place when he considered their reproductive interests from their viewpoints.

. . . In the early 1970s, then, Trivers was standing on the shoulders of giants, looking with a gimlet eye over a rich array of poorly explained animal behaviour (not excluding humans, since he had recently binged on novels). In this virgin landscape, the implications of the overlapping conflicts of genetic interests were waiting to be discovered, foreshadowed in scattered passages from Hamilton and Williams. Someone had to see them first, and Trivers was there.

. . . But Trivers rapidly spotted what everyone else missed, and still misses, together with the less biologically obvious concept of self-deception, so there must be another piece to the puzzle. During his junior year at Harvard, Trivers suffered two weeks of mania and then a breakdown that hospitalised him for two months. Bipolar disorder afflicted him throughout his life. I can’t help but wonder whether Trivers’s fecund period was driven by episodes of hypomania, when ideas surge and insights suddenly emerge through clouds of bafflement.

I had never thought of that, though Trivers made no secret of his diagnosis.  Finally, a bit about his behavior:

Though his upbringing was patrician and cosmopolitan (son of a poet and a diplomat, schooled in Europe and then Andover and Harvard), he was afflicted with a strong nostalgie de la boue. This contributed to his adoption of Jamaica, originally the site of his research on lizards, as a second home. Trivers’s life in Jamaica was filled with boozing, brawling, whoring, and of course toking, together with a stint in jail and a narrow escape from death during an armed robbery. His memoir Wild Lifeis peppered with homicidal fantasies and expressions of admiration for thuggish vigilantes, including Huey Newton, co-founder of the radical Black Panther Party. Trivers befriended Newton, made him godfather of his daughter, coauthored a paper with him on the role of self-deception in a fatal plane crash, and became a white Black Panther himself before Newton ushered him out of the organisation for his own safety.

. . . But Trivers’s neuroatypicality shaded into eccentricity and downright boorishness. He might try to drop off a passenger without stopping the car, or miscount the number of dinner guests and force two of them to share a chair. He repaid the colleagues who offered him professional lifelines at their universities with truancy, belligerence, and gross inappropriateness (greeting female students in his underwear when they had been sent to his apartment to fetch him to a late lecture; requesting that straitlaced academic hosts supply him with cannabis). His violent musings could make acquaintances genuinely fear for their safety. His last graduate student, Robert Lynch, spoke for many when he ended his affectionate obituary, “I’ll miss you, Robert. You asshole.”

. . . As for himself, Trivers liked to poke fun at some of his eccentricities and indignities. But he never squarely faced his record of betrayals, hurts, and squandered talent. All this is exactly what Trivers’s greatest theoretical brainchild would predict.

That “greatest theoretical brainchild” must be self-deception, of course, but I think that was perhaps the least important of his contributions.

Trivers’s had an erratic life, but also a rewarding one and a tumultuous ones. It makes me want to paraphrase Nagel: “What was it like to be Robert Trivers?”

There is also a shorter obituary in The Times of London, which you can see by clicking below or reading it archived here. Although author Finkelstein is not a biologist, he does a pretty good job summing up Trivers’s contributions, though he concentrates too much on the deceit and self-deception part, seeing it mirrored in modern politicians like Donald Trump and Liz Truss. If you want a short read it is okay, but given the choice, you should read the longer Pinker obituary. It will also teach you a lot about modern evolutionary psychology—known as “sociobiology” when Trivers and I overlapped at Harvard.

Luana’s revealing class survey of the biological definition of sex

March 17, 2026 • 9:30 am

Yesterday I wrote a bit (well, more than a bit) about a dire paper in Ecology Letters promoting a unusable “multivariate” view of sex and criticizing the gamete-based definition of biological sex recognized by most savvy biologists as the best definition, corresponding to reality, being universal, and being the most useful definition in promoting research. Sadly, but perhaps understandably, the average person wouldn’t be able to define “biological sex”, though.  This was demonstrated yesterday by my colleague Luana Maroja, an evolutionary biologist who works at Williams College in Massachusetts.

This semester Luana is teaching Evolution to undergraduates, and, fortuitously sent me the slide below with a note:

Today I taught about sex binary in Evolution.  Here is the clicker slide I presented and the responses:

A “clicker slide” is one which gives students in the class a chance to vote on alternatives. Each student has a device that records their vote. In this one, Luana asked her students to choose one of five alternatives to answer the question, “How many biological sexes in animals and vascular plants?” (Note that “biological” is in italics; she’s not talking about gender but gave the students the chance to conflate sex and gender. They have five choices:

 

A.  Binary (males and females)
B.  Three sexes (males, females, and intersexes)
C. 4 sexes (males, females, intersexes, and hermaphrodites
D. Over 150 sexes (from “agender” to “zoogender”) .
E. Impossible to tell since sex is a continuum.

First the five alternatives were presented and then Luana put a box around the correct answer, which is shown below (click to enlarge):

 

Note that by far the most common answer was C:  four sexes: males, females, intersexes, and hermaphrodites.  The correct answer, two, was less than half of that at 21%, followed by a tie of 14% for “three sexes” and “over 150 sexes.”  The “impossible to tell because sex is a continuum” answer garnered only 7% of the votes (in this small class that is just one person): I guess the students have not yet been propagandized by the likes of Agustín Fuentes and Steve Novella.

Intersex individuals do not represent a distinct biological sex because their sex is indeterminate, while hermaphrodites are simply individuals that have both sexes (both gamete types) in single individuals. They are common in plants but, since they produce sperm and eggs only, and not any other types of gametes, combine both functions in one individuals. Hermaphrodites are quite rare in animals though more common in groups like worms.  “True hermaphrodites”—individuals capable of delivering both types of gametes—are not present in mammals, and I’ve found only a handful humans with both testicular and ovarian tissue, none of which had viable gametes of both types.

These students are smarter than the average American because Williams is a highly rated and selective undergraduate college. Nevertheless, they have no idea that sex in animals and plants is a binary representing two types of gametes: a large immobile gamete, characterizing females, and a small, mobile gamete, characterizing males.

You can see why so many people are susceptible to people who argue that sex is not a binary: they are already predisposed to believe that.

Luana asked me to mention that “the class is small and this is an improvement over what I had two years ago (the last time I surveyed the students). At that time most people chose the last option.”  (continuum). When I asked her what the improvement was, she added that, “The improvement is because they are not answering E anymore and many more people are picking the correct response.  ‘C’ is not as bad as ‘E'”

But note this other info from Luana, “With a small class like this one, we really don’t know where the bulk of students stand, but it is also important to notice that this is a 300 level class, thus all students already had Biology 102 (organismal biology) and thus should know better.”  Bio 102 is apparently not doing its job!

Of course you’ve learned by now that the entire debate about how many biological sexes there are is spurred solely by ideology.  If gender activists were not so eager to promote the incorrect idea that sex and gender are the same thing, and that we should confect scientific definitions to match people’s view of themselves, then biologists wouldn’t be arguing about this stuff. Alas, even some biologists (I’ve named two) have been seduced by the sirens of ideology. Others include the Presidents of the three major evolution societies. As I wrote on February 13 of last year:

. . . . the Presidents of three organismal-biology societies, the Society for the Study of Evolution (SSE), the American Society of Naturalists (ASN) and the Society of Systematic Biologists (SSB) sent a declaration addressed to President Trump and all the members of Congress. (declaration archived here)  Implicitly claiming that its sentiments were endorsed by the 3500 members of the societies, the declaration also claimed that there is a scientific consensus on the definition of sex, and that is that sex is NOT binary but rather some unspecified but multivariate combination of different traits, a definition that makes sex a continuum or spectrum—and in all species!

As it happened, a letter with about 125 signers from the evolutionary biology community took issue with the embarrassing “sex spectrum” claim, and the Tri-Society presidents decoded to remove it from the Internet, though I archived it and you can see it at this link. It stands as depressing testimony of how even influential evolutionary biologists can distort science when they want to conform to an au courant ideology.

But enough; the survey above gives you an idea of the extent of public misunderstanding of biological sex.

Bob Trivers died

March 15, 2026 • 7:42 am

. . . at least according to this post from Quillette and response from Steve Stewart-Williams. And, as I wrote this short post, his Wikipedia bio was updated to show that he died on March 12 at 83.

I knew the guy, though not well, and he was a complex individual, capable of making great advances in evolutionary theory (early in his career) but also to self-sabotage.  I have stories about him, but I can’t really recount them here.  I’ll just put up the first two paragraphs of his Wikipedia bio in lieu of an obituary. Unfortunately, it shows he was in the Epstein files (but so was I):

Robert Ludlow “Bob” Trivers  born February 19, 1943) is an American evolutionary biologist and sociobiologist. Trivers proposed the theories of reciprocal altruism (1971), parental investment (1972), facultative sex ratio determination (1973), and parent–offspring conflict (1974). He has also contributed by explaining self-deception as an adaptive evolutionary strategy (first described in 1976) and discussing intragenomic conflict.

Some of Trivers’ work was funded by Jeffrey Epstein, and Trivers later defended the convicted criminal’s reputation.[3] In 2015 he was suspended from Rutgers University after he refused to teach an assigned course.

My answers in a Mexican newsletter to questions about evolution

February 25, 2026 • 10:45 am

Not long ago I was asked by Jason Flores-Williams to contribute to his online/free paper newsletter Alma Asfalto, a Mexican publication (translation: “asphalt soul”) that has English translation. Flores-Williams wanted me to answer a few questions about evolution, and I agreed for two reasons. First, I wanted to help promote the understanding and acceptance of evolution among our southern neighbors. Second, if you click on the first link (to Wikipedia), you’ll see that Flores-Williams is a guy worth helping:

 Jason Flores-Williams (born 1969, Los Angeles, CA) is an author, political activist, and civil rights attorney. He is best known for his legal work on behalf of death row clients, political protesters, the homeless population of Denver, and his suit to have the Colorado River recognized as a legal person. Flores-Williams is an acknowledged expert in conspiracy law and First Amendment cases whose views are frequently sought by media organizations, including the Washington Post, the New York Times, and the Los Angeles Times. He was also a lead organizer of the protests against the 2004 Republican National Convention. He lives in Denver, Colorado.

How could I refuse a guy who did that? And so I agreed, answering his five questions. These answers appear on pp. 6-7 of the 16-page March edition of the paper, along with interviews and short essays by other scientists and humanities folks (these include author and filmmaker Sasha Sagan, the daughter of Carl Sagan and Ann Druyan). I’ll give here the five questions I was asked, but to see my answers you must to the paper by clicking on the screenshot below. (You can also download the whole paper. Warning: the site loads slowly.)
 

Here are the questions I was asked. Again, see the answers at the site.

  • In the simplest terms, what is evolution—and what do people most often get wrong about it?
  • Why does evolution still make some people uncomfortable, even though it’s one of the most well-supported ideas in all of science?
  • Does accepting evolution make human life feel less meaningful—or, in your view, more remarkable?
  • People sometimes say that evolution promotes selfishness or brutality. What does evolution actually tell us about cooperation, empathy, and morality?
  • If you could change one thing about how evolution is taught or talked about in public life, what would it be—and why does it matter right now?

Here are the contents:

Mexico City
March 2026 

Reality is being branded.
Truth manipulated.
Disengagement marketed.
But something real is gathering.

Across science, philosophy, art, and film, the real is now contested ground.

https://almaasfalto.com/marzo/

REALITY

Sasha Sagan
— The Integrity of Uncertainty

Zona Maco
— Art Week, Mexico City

Jerry Coyne
— Evolution and Meaning

Vlatko Vedral
— The Universe Owes You No Certainty

Asya Geisberg
— Necessary Friction

Franco “Bifo” Berardi
— Desertion from the Future

Kevin Anderson
— Against the Illusion

Mariana Rondón
— It Is Still Night in Caracas

Sarah Martinez
— Alchemist of Nothingness (FR/ES)

Printed in Mexico City.
Alma Asfalto circulates in Roma, in the Historic Center, and underground, on Metro platforms.