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):

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:

“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.

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.

. . . 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.

RIP Robert Trivers (1943–2026), one of the boldest and most influential thinkers in evolutionary biology.

A giant in the field—whose ideas reshaped how we understand cooperation, conflict, and human nature. https://t.co/N4dV7cOSrk pic.twitter.com/xzWNKTi8Q2

— Quillette (@Quillette) March 15, 2026

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.