Prof. William Donald (Bill) Hamilton, 1936-2000
Richard Dawkins summarises Hamilton's professional "vital statistics" so well in the obituary he wrote in honour of the latter that I shall simply borrow the entire paragraph from him:
William Donald Hamilton FRS was Royal Society Research Professor in the Department of Zoology at Oxford, and a Professorial Fellow of New College. He was born in 1936, spent a happy childhood botanising and collecting butterflies in Kent, was educated at Tonbridge, then Cambridge where he read Genetics. For his Ph.D. he moved to London where he was jointly enrolled at University College and LSE. He became a Lecturer at Imperial College in 1964, where his teaching skills were not highly rated. After a brief Visiting Professorship at Harvard, he accepted a Museum Professorship at the University of Michigan in 1977. Finally, in 1984 he moved to Oxford at the invitation of Richard Southwood, who had been his Professor at Imperial.
So much for fact. But there is a certain amount of legend, or rather mythical glory
, to Bill Hamilton. Anyone reading even the most popular of popular books about evolution is sure to come across his name almost as often as across that of Darwin
himself. Hamilton had, among innumerable other achievements
, helped shed light on two of the biggest problems Darwin came up short against: altruism
The story of Hamilton, the lonely graduate student, distanced from his peers due to his own superior intellect and misunderstood and underappreciated by his teachers is so famous as to be almost apocryphal - although it's apparently perfectly true. He wasted a lot of time being underappreciated, and the paper he wrote on the subject of genetic reasons for altruism almost went unpublished - and after publication went largely unnoticed for almost a decade. Hamilton's idea was so simple, it was pure genius: organisms cooperate, and even sacrifice themselves to save their relatives, because they share the same genes. Genes that tell them to cooperate! Any gene that encourages one organism to help its relatives will spread more quickly through a population, for the simple reason that those who carry it and their relatives will help each other survive and reproduce more than those who don't.
It is also postulated, in what is now known as Hamilton's Rule, that there is a strict mathematical principle governing the amount of self-sacrifice an organism will be prepared (or conditioned by its genes) to put forward, and that this is connected to the relatedness of the organism to those it's helping. Every organism shares a certain average precentage of genetic material with its relatives - the closer the relation, the more genes it shares. You take half of your genes from each of your parents, therefore you are %50 related to them (a well as to your children). You will therefore be more likely to sacrifice the chances of your own survival to save any siblings or children, as well as parents, than you would be to save cousins or nephews - they have ancestors you do not share and therefore are more likely to have genes you have no stake in perpetuating. The mathematics governing this seemingly simple principle are actually quite complex, and Hamilton's original paper on the subject is often quoted but seldom read ( a little like Chomsky's work in linguistics), because there aren't a lot of biologists who know enough math. Nevertheless, it solves one of the greatest riddles in evolution: if natural selection is so competitive, and survival of the fittest so paramount, how come male spiders allow themselves to be killed in order to serve as food for their young? How come birds often stay in the nest and help rear the next generation of their siblings rather than go out and have their own young? It's all very well to talk about the maternal instinct, but why is it so prevalent?
The theory which reigned in the generation of Hamilton's teachers and peers was one of "group selection" - broadly what this means is that evolution works for the benefit of the species as a whole, or at least of a distinct population. Natural selection "selects", as it were, the fittest among the species in order to perpetuate it. Hamilton was among the first to see how nosensical this idea was - after all, for natural selection to think and plan and observe in such a way, it would have to be God. But natural selection doesn't have foresight, it doesn't plan or compare. It is a convenient name for a series of random and unconnected events. It cannot be said of itself to postulate that all mothers are somehow made with the instinct of protecting their young (anyway, it's not true - reptiles don't mother). The idea that inter-generational altruism, and by extension, social behaviour in general, can be postulated by an individual's DNA not only gave answers to ancient questions, therefore: it also opened entirely new avenues of thought. It essentially opened the door to Dawkins and his selfish genes, as well to an understanding of how society, even human society, can be a direct result of evolution on the gentic level.
Dawkins was not only influenced by Hamilton, he admired and advocated him greatly. As it is fair to say that his The Slefish Gene is right up there with A Brief Hisotry of Time at the top of the all-time popular science best seller list, my raving about Hamilton's innovation might seem like preaching to the choir. But at the time it was a mjor scientific revolution, one that prompted a complete paradign shift in the biological community - from group selectionism to gene selectionism. The second of Hamilton's great achievements is a little less famous, a little less clear, a little less dramatic (what with the tear jerking stories of the misunderstood student moping over his papers on a bench in the park), and a bit more contentious, being still relatively new.
Why do organisms have sex? It's not mandatory, after all. Dandelions don't, for example. Female aphids give birth to daughters already pregnant with the next generation without any help from another sex. Strawberry plants can take it or leave it, as the spirit takes them. The cost of sex is astronomical: while an all-female progeny capable of parthenogenetic reproduction can all go out and breed, a generation of sexually produced males and females will contain one half (the males) who cannot. In the game of evolution, so obssessively controlled by one's genes desire to propagate themselves, this is an almost lunatic price to pay - a full %50 of one's reproductive potential. The hackneyed answer to this question, one which is still taught to school children, is that sexual reproduction, because it involves the mixing of genes from two parents, provides a greater variety of genes for natural selection to choose from, thereby improving the chances of survival of the descendants.
On the surface, this seems to make sense. Evolution is all about adaptability, and with sex comes a greater opportunity for adaptation, because it provides a wider range of muations for natural selection to work on. So, if I were to give birth to children who are identical to me, and our environment were to change slightly, then they would be at a disadvantage - their continued survival will be dependant upon random mutations which they will then be able to pass on to their own descendants. If I were to mix my genes with those of another individual, however, they would not only have twice as many traits ad twice as many potential mutations to work with, the chances of some of them inheriting two different mutations which will help them survive will be immeasurably greater than the chances of those two mutations both spontaneously arising in the same individual.
But hang on a minute. The environment doesn't change that fast, after all. They've been talking about the climate changing ever ince I can remember, but it hasn't really changed yet - not according to all but anecdotal evidence. Yes, parts of Africa are becomign more arid, but research shows that this is in some part a ciclical phenomenon which waxes and wanes with the decades. Humans and other apes only have one child every couple of years at best - which means that in evolutional time, these changes go past in an eyeblink. Neither do predators and prey evolve fast enough, even with sex, to justify mixing up a formula which already works (my own obviously successful DNA) with something else and trusting to change to make it profitable. The price it too high, the potential gain too low.
For years this conundrum puzzled biologists. At the time of the writing of The Selfish Gene, you'll notice, there was yet no satisfactory answer. Dawkins even reluctantly admits that sexual selection is the only remaining weapon in the arsenal of the group selectionists - animals have sex for the long term gain of the species. But evolution has no foresight! So what is really going on here?
The answer, which has recently been pretty much accepted as true, is that there is one part of our environment that changes much more quickly than we (or other animals) do - our parasites. We all know how fast bacteria reproduce. By the time I die, the bacteria in my gut will have gone through thousands and thousands of generations - evolutionally, a good time span to have adapted to me perfectly. But not all the bacteria in my body are good for me. We all carry all sorts of parasites and diseases with us, from tapeworm to AIDS, which make their living by staying one step ahead of us in the evolutionary arms race. Now, it is a fact that a mother will pass on her parasites to her child - in the bood, in milk, in the very egg that is bein fertilized or even in her breath and skin while she tends to her young. What mother in her right mind will want to also pass on the very genes to which those parasites are best adapted?
The immune system is the most changeable and transient of all genetic legacies. Not only is its variety helped along by the normal Mendelean heredity, there is an extra special bit of crossing over that the chromosomes in one's sex organs do before splitting into sex cells (eggs and sperm). First the mix up all the genes to do with the immune system reall good, and only then do the split in half and leave a completely unique cocktail for the next generation's parasites to deal with. The discovery of this peculiarity of heredity in regard to the immune system beautifully bears out the above theory.
Many different scientists are credited with having this idea occur to them, but it was Bill Hamilton who pursued it until he could prove it. He coopearted with two colleagues in the US to build a computer model of an environemnt which for the first time included parasites, and through it demonstrated the plausibility of parasite adaptability. He is consequently more associated with the coup of finally coming up with an answer to sex than pretty much any other scientist.
I don't know if I have managed to give a good impression of what a genius Bill Hamilton was. He was insightful and thorough, brilliant and hardworking all at the same time. Scientists are notoriously quarrelsome people, but nowhere have I read anything bad about Hamilton - by all accounts, he was a great guy as well as everything else. The ideological implications of his work are already being felt in our society, and I am sure that they will grow in influence and dominate this century as those of Darwin did the last.
The full obituary by Richard Dawkins can be found at http://www.edge.org/3rd_culture/hamilton/hamilton_index.html