The Price of Altruism (23 page)
Read The Price of Altruism Online
Authors: Oren Harman
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,
r
B > 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” nothing 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.
Walking nature’s trails, Hamilton was once again where he wanted to be. It would take nine months to resubmit the corrected manuscript, “The Genetical Evolution of Social Behavior, Parts I and II.” Oblivious to the world, he did not know that in that space of time John Maynard Smith, citing only the shorter
American Naturalist
article, wrote and published “Kin Selection and Group Selection,” giving “inclusive fitness” its catchy name. Nor, of course, did he know that Maynard Smith had been the anonymous reviewer responsible for its delay. When he did find out, it would ignite in his humble soul a feeling it rarely countenanced. But this was still far off in the future. “Very probably,” he later wrote of the present,
the sun of the day that saw my paper going into the post from JTB…would have seen me weaving my old American jeep between the corrugations, stones, and potholes of the Belém-Brasilia road…. At midday it would have blazed near vertically on the top of my head as I stopped at the roadside and collected wasps from some nest; later at sunset, if still able to pierce the haze, it would have seen me and my Brazilian companion…slinging our hammocks between low cerrado trees not far from the stony or sandy piste where occasional lorries still groaned on into the night. For sure, both that day and that night I was blissfully untroubled about the finer points of measuring relatedness.
44
No one hated group selection more than George Williams. A lanky American fish specialist with the beard-but-no-mustache look of what some described as an Easter Island statue, he was determined to fight Wynne-Edwards. As a student he’d heard a talk by Emerson: Death, the Chicago man argued, was an adaptation for the good of the group. Williams wouldn’t believe it. Organisms dying just to “get out of the way”? That couldn’t be right. “If this was evolutionary biology,” he said to himself, “I wanted to do something else—like car insurance.”
45
Across the Atlantic in Oxford, meanwhile, Lack was doing his damnedest to put the notion of the “greater good” to rest. There was no reason to assume with Wynne-Edwards that birds restrain their reproduction to strengthen the group. If a mother bird produced a smaller clutch of eggs, it wasn’t because she was in cahoots with all the other mothers to lessen the number of progeny. On the contrary, if resources were slim that year, it made perfect sense to sire fewer younglings in order to be able to care properly for those who were born: In a season of dearth, a mother might feed three goslings to health, whereas if there were seven all might die of hunger. No, natural selection didn’t fashion adaptations for the good of the group; always, inexorably, it was “looking out” for individuals.
46
It was 1966. Nine years earlier Williams had worked out a model, better than Wright’s, that revealed the conditions under which group selection might work.
47
But like Maynard Smith he’d become convinced that while possible theoretically, it was improbable in nature. Lack was right: If behavior could be explained by selection working at different levels, there was no reason to choose the higher level over the simpler one. Walking Occam’s razor, the evolutionist should be guided by parsimony.
However powerful a tool, though, parsimony was a matter of interpretation; it was difficult to settle unequivocally whether selection was working at the level of the individual or the group. What Williams really needed to kill group selection was a prediction that could generate a natural test. And he found what he was looking for buried in a paragraph in the pages of
The Genetical Theory of Natural Selection
.
48
Fisher had argued that sex ratios in any species should always evolve to an equal number of males and females. The reason was simple: A male born into a species with a female-biased sex ratio is at an advantage, since he has more mating opportunities than a female. If genes determine sex, then in a population with more females, the male-making gene will be favored by natural selection. Eventually the frequency of that gene will reach a point where the sex ratio of the species is now male-biased, whereupon its alternative, a gene promoting the production of females, will be favored. The dancing dialectic would ensure a symmetry of sexes: The wisdom of selection fashions males and females one-to-one.
Even though he didn’t know it, Fisher was playing a game, just like the ones John von Neumann loved. Whether a mother should produce a son or a daughter, after all, depended on what other mothers were doing—the requisite condition for the application of game theory. But beyond the convergence of economics and biology, what Williams now saw was that Fisher had done a blessed service: Figuring out the logic of the symmetry of the sexes, he’d delivered the deathblow to the notion of the “greater good.”
Here is why: Imagine a mother parrot mating and then flying off alone to a deserted island in the middle of the sea. Imagine that she lays 10 eggs, half of which hatch into males, the other half into females, and imagine that her daughters do the same. What will happen? The population will grow rather quickly: From 10 in the first generation, it will balloon into 50 in the next (25 females and 25 males), 250 in the generation after that (125 of each sex), and so on.
49
But what if the mother parrot lays 10 eggs that hatch into 9 females and just 1 male, and her daughters do the same: How then would the population grow? In the first generation, as before, there would be 10 parrots (9 females and one male). But in the next generation there would be 90 (81 females and 9 males) and in the one after that 810 (729 females and 81 males). Compared with a 1:1 sex ratio, a female-biased ratio would run much faster. Before long the island would be teeming with parrots.
But there was a twist. Even though siring more females would benefit the growing group, it would actually reduce the individual fitness of the mothers who did so. Imagine two mother parrots arriving on the island: Linda sticking to the 1:1 sex ratio, Barbara to the 9:1. Together they will produce 20 offspring in the first generation: 5 + 9 = 14 females added to 5 + 1 = 6 males. When these off spring mate among one another, while each female continues to lay 10 new eggs, the average male sires 23 children (140 divided by 6), since he fathers the offspring of more than 2 females. The results for Linda and Barbara are surprising: After three generations, Linda, who stuck to the slower 1:1 sex ratio but had more males, will have 165 grand-offspring whereas Barbara, who went for the 9:1, will have only 113.
When it came to the sex ratio there was a conflict between community and individual: If the group counts, “altruistic” Barbara is the winner, but if the individual is selection’s client, “selfish” Linda prevails. Wynne-Edwards had shown that in times of dearth it is not always to the advantage of the population to breed as much as possible. But assuming sex ratio was an adaptation, when the times of dearth were over one would expect a switch to a female-biased sex ratio. Scouring the literature, Williams saw that this never happened—not in flies, not in pigs or rabbits, not even in humans. Over time and across all vagaries the 1:1 sex ratio remained stable—the very prediction that selection working to maximize individual fitness required.