The Price of Altruism Page 18
This kind of “gene’s-eye” view of evolution he had inherited from Haldane, which was perhaps why the editors of the Journal of Theoretical Biology had sent him a paper by Bill Hamilton that had left two other reviewers completely baffled and perplexed.
Thanks to the unusual social life of the Hymenoptera, “The Genetical Evolution of Social Behaviour” introduced an original idea. For the better part of the century classical population geneticists had defined “fitness” as the measure of an organism’s reproductive success: The more off spring an organism sired, the greater its fitness. A corollary of this definition was that the persistence of any behavior or gene responsible for it which reduced an organism’s fitness would be difficult to explain: in time, as was her mandate, natural selection should see to its demise. But Hamilton now showed that if fitness were redefined to include the progeny of relatives rather than just one’s own, in many cases the Darwinian difficulty of explaining the evolution of altruistic behavior would simply disappear. The key was adopting a “gene’s eye” point of view, and the Hymenoptera showed precisely why.
In the ancient order—comprising sawflies, wasps, bees, and ants—female workers are more closely related to their sisters than to their offspring due to a genetic quirk in their sex-determining heredity called “haplodiploidy.” All females are born of eggs fertilized by sperm and are diploid (meaning that they possess a full compliment of chromosomes from both their mother and father), whereas all males are born of unfertilized eggs and are haploid (meaning that they have no father but rather only a single set of chromosomes from their mother). Since female sister workers share all their father’s genes and half their mother’s, their coefficient of relationship is r = 0.75, whereas since they pass only half their genes on to the next generation the relationship to their off spring is r = 0.5. Brothers and sisters, on the other hand, only share one common ancestor, their mother, and are therefore only half as related as normal siblings, with r = 0.25.
The implications were strangely illuminating. Lazy male drones were not moral slackers but genetic opportunists: They spent their time seeking to mate rather than work since their relatedness to off spring would be double their relatedness to any sisters they might oblige. Female workers, too, were shrewd genetic calculators. Neither shirkers of parenthood nor mindless toilers, farming the queen as a “sister-producing machine”24 served their interests more generously than did siring their own brood. Everything depended on perspective: From the point of view of the gene trying to make its way into the next generation, it made absolutely no difference in whose body it was being carried. In one stroke, a century after Darwin, “inclusive fitness” unveiled the mystery of the ants.25
But Hamilton didn’t stop there; the Hymenoptera, after all, were just an illustration. Trudging through pages of algebra he had come up with an elegant equation. It sounded almost economic: Every altruistic act—such as a rabbit thumping its legs to warn its friend of the presence of a predator, or a howler monkey doing the same with its call—would entail both a fitness cost to the altruist (the chance that he might attract the predator himself), and a fitness benefit to the receiver (the chance to live another day and produce more offspring). What Hamilton showed was that, for every social situation, if the benefit (B), devalued by the relatedness between the two (r), was greater than the cost (C), genes responsible for altruistic behavior could evolve. The greater the relatedness the greater chance for altruism. With the help of the mathematics of genes, rB > C formalized what Darwin and Huxley and Fisher and Haldane had all intuited: altruism was a family affair.
Boom!
Thrown to the ground, he took a moment to notice the blood soaking his shirt below the chest and oozing from his mangled hand. There was sawdust, and smoke, and the unmistakable bittersweet taste of gunpowder. He could hardly see through the haze and was growing woozy.26
William Donald Hamilton was born in the summer of 1936 on a small island in Egypt’s Nile to Bettina, a physician, and her husband, Archibald, a military engineer, both of them New Zealanders. After they discovered that army life was neither their inclination nor priority, they’d settled in a cottage on Badgers Mount, at the rural edge of the North Downs, County Kent, England. Bettina quit medicine to raise a family—there was his sister Mary and four more children on their way, and Archibald set up a bridge design business, gaining his growing family a steady income from the prefab steel Callender-Hamilton used by army tanks to gallop across ravines in World War II.
Archibald had taken away the rusty tins filled with explosive powder Bill unearthed in a rabbit burrow a few days earlier and stashed them in a shed. But it was too little to stave off his son’s curiosity. Now, just as he was clamping a powder-filled brass cartridge with a vise, it blew up. With his last ounces of strength, he dragged himself into the house and collapsed on the kitchen floor. He was twelve years old. There was shrapnel in his lungs, and the tips of three fingers were missing. He would live. Risky business was a Hamilton family trait.
“Oaklea,” named after Archibald’s old New Zealand dwelling, was a cramped home whose inhabitants were tinkering and practical, and “as far as possible, a self-supporting republic.” You wouldn’t find a plumber invited, nor a carpenter, a welder, or an electrician. Nor, for that matter, could you find a proper room; Bill usually slept on an army cot in the corner of the dining room, or, when the frosty winters gave way to the cool evening breezes of spring, in one of the many tool sheds surrounding the cottage. In a dry creek or beneath a large piece of birch bark or in a cozy burrow would do; sometimes he’d forget to come home at night from his lost-to-the-world natural explorations. Walking barefoot and oblivious down woodland paths “chasing clouded yellow butterflies through fields of red clover,” Bill was happiest among plants and insects. The Hamiltons were fiercely independent, highly spiritual, unsentimental people. Bettina had a keen interest in natural history, and clearly she’d passed it on to her son.27
But young Bill had inherited his father’s aptitude for math, too, even if he thought he was no good at it.28 When he arrived at Cambridge he decided to read Genetics, the better to combine the two, but not before he’d requested the Origin of Species as a school prize.
He was following in Fisher’s footsteps. Soon, accompanied by awe and trepidation, he discovered Fisher himself, white haired in carpet slippers in his room at Saint John’s. The meeting between the two never developed into a relationship, however; Fisher’s mind, it seemed, was by this time somewhere else. Hamilton’s encounter with The Genetical Theory of Natural Selection, on the other hand, had been positively transformative. “This is a book,” he later wrote, “I weighed as of equal importance to the entire rest of my undergraduate Cambridge BA course.”29 It was also a book not taught at Cambridge, where one of his professors representatively acknowledged Fisher’s importance as a statistician but wondered out loud whether he had any qualifications in biology. In zoology, it seemed, the “good of the species” had conquered everything, another professor’s book starting: “Insects do not live for themselves alone. Their lives are devoted to the survival of the species whose representatives they are…,” and so on. Fisher’s emphasis on natural selection always working at the level of the individual was ignored. Even natural selection itself was scarcely respected anymore at Cambridge.30
And so Bill Hamilton did what he had always done as a boy in the woodlands: strike his own path. To his sister Mary he admitted that Fisher’s mathematical reasoning was “rather beyond me,” but he plugged away nonetheless, spending months in solitude on each chapter. The eugenic bits on civilizations, especially, had snagged him. “I now know why they decline, and how to stop them,” he wrote to Mary. Cultural progress, he had suckled from the bosom of his hero, depended on natural selection.31
A convert to evolution by natural selection working to maximize individual fitness, he’d need to tackle the kind of behavior Darwin himself said would annihilate his theory completely if even one instance of it could be
convincingly documented.32 He had read Fisher on butterfly distastefulness and Haldane on drowning cousins, and yet, he’d later remember, “one reads and forgets.”33 After all, however comprehensive the two giants’ treatments of evolution, they had devoted only a few paragraphs to the problem, and surprisingly not attempted a comprehensive mathematical model. Besides, treating it as a phenomenon related to Military Cross winning, as both had tended to do, seemed to confuse things. Still, clearly, Hamilton thought, the genetics of behavior was a subject relevant to animal and plant as well as man. If the geneticists at Cambridge didn’t see the point, or the social anthropologists what connection it had with genetics, he would go elsewhere to pursue his puzzles. Just twenty-two, a gentle and shy loner with a shock of thick hair, workman’s hands, massive jaw, and the general appearance of a Neanderthal, Bill Hamilton had found his problem: the evolution of altruism.
Already he knew: Feelings for family are not the same as for strangers. As the badgers for whom the hill of his childhood was named made famous, protecting kin was a risky but prevalent affair. Why should this be so? Pondering the question, he put in an application to become a teacher, just as Fisher had done before him. But his genetics degree, the good people at the School of Education at Moray House teachers’ training program in Edinburgh informed him, would only qualify him for junior high. Cuddling the snub, he thought about becoming a carpenter.
Finally he walked into the office of Lionel Penrose, Galton Chair of Genetics at University College London. Haldane was by now working at the Indian Statistical Institute and living in an ivory tower in Orissa. No, Penrose intoned coldly to Bill, he didn’t see the connection between a moral trait like altruism and genetics. Recently he’d changed the name of the Annals of Eugenics to the Annals of Human Genetics, and would have no talk of genes for human behavior. At best the genetic evolution of altruism was a waste of time; more to the point, it was pernicious. Morphology was one thing, but hadn’t the Third Reich been enough?34
Whether Penrose really believed this, Hamilton was not certain. The times had seen a strong environmentalist backlash, but to him it all seemed maudlinly political. He had a sneaking suspicion that, as in the old Punch cartoon, Penrose was trapped and wishing it all to go away: “Have you heard that Mr Darwin says that we are all descendant from the ape?” one shocked Victorian lady asks the other. “Oh, my dear—that surely cannot be true!…But, if it should be true, let us pray that at least it will not become generally known!”35
To contemplate the biology of character was to think “the socially unthinkable” after Mein Kampf and the Final Solution it was positively verboten. At stake, rather than religion in Darwin’s day, was the egalitarian premise of democracy, not to mention the delicate politics of race. Penrose acknowledged a Cambridge genetics degree, and offered Hamilton work on classical fly genetics; for the evolution of altruism he’d need to go elsewhere. Luckily, unlike Penrose, Professor Norman Carrier of the Department of Human Demography at LSE seemed “quite unaware of even a possibility that I might be a sinister new sucker budding from the roots of the recently felled tree of Fascism, a shoot that was once again so daring and absurd as to juxtapose words such as ‘gene’ and ‘behaviour’ into single sentences.” The friendly Carrier didn’t quite grasp the project but was encouraging and helped Bill secure a studentship.36
He was deeply lonely. Enrolled as a doctoral student in two separate departments and institutions, he spent hardly any time at either. With no office space and virtually no one in the corridors or libraries knowing his name, he did most of his work alone in his bed-sit in Chiswick, or, when the sun came out and—struggling to keep the pages from blowing away in the wind—on a bench at Kew. At UCL Penrose projected a “kind of gloomy avoidance,” so the friendly but rather absent Professor Cedric Smith was assigned as his formal supervisor. At LSE Carrier was replaced by the mathematically apt but biologically innocent John Hajnal. Bill was on his own, walking the narrow bridge of obscurity. Unable to distinguish the conviction that he had seen something that others had not seen from the suspicion that he was nothing but a crank, Hamilton teetered on the brink of despair.
Some nights he’d stop on a bench at Waterloo Station, back from Holborn Public and the Senate House—the late libraries—not wanting to return to his depressing quarters. There, at least, the waiting passengers in the main hall gave him some comfort. Scribbling out his mathematical model with pencil in notebooks, Bill felt less alone.
Partly to save money, partly for exercise, and partly to conjure somehow, “below the bricks and mortar around me, the marshy fields that had once been there, the streams dividing them, and the heaths behind—to seek, in short, elemental forces underlying the city,” he walked London through and through:
Even a lonely child on the street did not tug my heart as hard as a bracken fern when I saw it, for example, in the valley of the stream once called the Fleet…. I recall also the soul-piercing yellow from the flat, star-like flowers of a ragwort. What plant was this, daring to flower under such hostile cliffs, where was it from? Was it a growth form of the more crinkled and robust plant I knew so well on the Kentish fields, there crawled upon and stripped by the stripy caterpillars of the cinnabar moth? But if the leaves in London might be laxer and greener because of a lack of light or to an excess of lead in these wells, why would the flower be larger?…I simply imagined that, like me, the plants were longing to be away from these dark concrete canyons, back in their own countryside. Fixed in their cracks, as I thought, what else was there for them but to signal desperately with their bright petals to the rare and equally lost London bees crossing (again like me) the chasm of the Farringdon Road? Was it through such petals and then such an insect’s aid that they hoped to create the seeds which an autumn storm could carry away?37
Bill Hamilton felt an intimacy with the outdoors that blurred the boundaries between himself and nature. Those who knew him couldn’t help feeling that this gentle giant was more comfortable in the presence of spiders than humans.
And then, from beneath the despair and reams of equation-filled notebooks, rB > C appeared. Others thought the idea behind it a “solvent of a vital societal glue,” but imagining himself a gene in the body of a toiling ant, Hamilton welcomed it as a “love child.” Finally, after Darwin and Fisher and Haldane, not to mention Penrose, he had cracked, in his painful solitude, the mystery of kindness to others.38
The paper sent to him by the Journal of Theoretical Biology was brimming with mathematical equations and natural history. The name Hamilton sounded familiar from UCL, but he remembered it rather vaguely.39 Not following the math too closely—the notation was unconventional and the typesetting confusing—Maynard Smith recommended splitting it in two. It was too long and needed revisions. Still, unlike the other two reviewers who hadn’t understood it, he was impressed by Hamilton’s insight. “Of course, why didn’t I think of that!” he exclaimed to himself, just as T. H. Huxley had done when encountering Darwin.40 Since he was presently writing a review of Wynne-Edwards’s book, he wanted to distinguish it from group selection. After all, a family is a kind of group, and “inclusive fitness” might be interpreted as just a form of group selection. A better term was needed.
Meeting with Lack and a few of his colleagues at Oxford to discuss the annoying excitement of many biologists over Animal Dispersion, Maynard Smith hit the jackpot.41 In “Kin Selection and Group Selection,” published in Nature, he proposed a combined verbal and mathematical model showing that the conditions necessary for group selection to work were so stringent that one would be hard pressed to find them in nature.42 A major obstacle was invasion: If amid a population of birds exercising population control suddenly appeared a bird who didn’t, little could stop it from procreating. Assuming its antisocial nature—since genetic—is passed on to off spring, before long the entire population would be comprised of self-seekers.
No, group selection was not the way social behavior evolved, the “greater good” nothi
ng but a hopeful, unworkable illusion. Kin selection, on the other hand, was a viable evolutionary mechanism.
Besides ants and monkeys and thumping rabbits there were moths. The theory predicted that camouflaged (cryptic) and brightly colored (aposematic) species should act differently immediately after siring kin. If caught by a bird, a cryptic mother would unwittingly be helping the bird learn the moth’s disguise, thereby making the bird more successful in catching the now exposed younglings. An aposematic mother in a bird’s beak, on the other hand, would only be doing a service to her kin: Since her colors are true indicators of a noxious toxin, the bird will have learned to stay away from similar-looking progeny. It made sense, on the “gene’s-eye-view” logic of inclusive fitness, that postreproductive cryptics should die much faster than postreproductive aposematics. Hamilton was delighted when he learned from the lepidopterist A. D. Blest that postreproductive cryptics have significantly shorter life spans, but only when they are surrounded by kin. The greater good was a fiction. And happily, more natural examples of his theoretical predictions kept rolling in.
Hamilton wasn’t a crank, then, after all, hallelujah!—though he’d convinced nobody except himself. It was 1963, and his Leverhulme studentship was ending. He had yet to publish a word. Eager to show something for his years of toil, he sent a three-page account that was rejected by Nature but accepted by American Naturalist.43 The much longer, detailed article he sent to the Journal of Theoretical Biology would cover all the bases when he got around to addressing the anonymous reviewer’s comments—the most important of which, he now read, was to split it in two. Meanwhile, following in the path of Darwin’s codiscoverer Alfred Wallace, he was off to Brazil to study social wasps in the jungle.