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In Memory of Bill Hamilton

Thought about 'Hamiltonian inspiration'

by Jacobus J. (Koos) Boomsma. Given at the closing symposium of the EU-TMR network "Social Evolution: An Integrated Study of Kinship, Communication, Productivity and Disease"

Right from the beginning in 1996, Hamiltonian thinking has been central to the organisation and prime interests of our Social Evolution network. Bill Hamilton's inclusive fitness theory, where kin-selection creates and maintains social systems of high relatedness has been the "alpha" keyword of our network. His later hypothesis that disease pressure may secondarily force advanced insect societies into looser family structures characterised by low relatedness has been the "omega". In between are key-words such as "productivity", emphasising that traits which are not efficient in the eyes of natural selection will not be maintained, and "communication, encompassing all the chemical interactions related to individual recognition that make insect societies work in a practical, proximate, day-to-day sense. Chemical signals are involved in issues of advanced cooperation and in issues of inter- and intra-colonial conflict, for example when allowing or disallowing discrimination between close kin, remote kin and non-kin. In addition, glands of social insects producing chemical compounds are actively involved in the control of diseases. In all respects, therefore, our network could hardly have been more Hamiltonian than it is.

Bill Hamilton would have been a guest of honour in this symposium and would have been among us today, had it not been for his tragic and untimely death earlier this year. Because of his unique contributions to science in general and to social insect biology in particular, it is only fitting that we dedicate this symposium to him and that we start out with commemorating aspects of his personality and his work. In a few minutes, Mary Jane West Eberhard and Luisa Bozzi will give their very personal tributes. As I have myself had the privilege to work in his close vicinity in Oxford during the academic year 1986-1987, I would also like to tell you my story about Bill Hamilton, hopefully providing an introduction to what Mary Jane and Luisa will say directly after.

Bill Hamilton's great merit has been that he has given us a synthetic evolutionary theory of social interactions. This inclusive fitness or kin selection theory, formulated in 1964 as Hamilton's rule, is so intuitively simple that many have reacted to it later in the terms used by Edward O. Wilson "Obviously that is true, but why didn't I think of it". The theory was controversial and largely ignored in the first 10 years after its publication. During the last 25 years, however, it gained so much support that it must seem almost unthinkable to young scientist now that it was ever problematic. Where a single successful theory of this calibre would already have been enough to permanently enter the history books of science as a giant, Bill Hamilton achieved much more. In his early career he made essential contributions to the evolutionary theory of ageing and the evolution of stable dispersal strategies. He was the first to think deeply about reproductive conflicts at the gene level, about evolutionary consequences of inbreeding, about spite and social selfishness. He was intrigued by skewed sex ratios, he proposed the concept of Local Mate Competition, and he made vital contributions to our understanding of reciprocal altruism. In the last twenty years of his life he introduced "parasite hypotheses" for sexual selection through female choice, for the evolutionary maintenance of sex, and for the increased genetic diversity of advanced insect societies with large colonies. Finally, he was deeply engaged in the quest to clarify the origin of AIDS. A field expedition to the heart of Africa in search of the chimpanzee population that transmitted the precursor of HIV-1 to humans made him contract malaria, the complications of which lead to his death in London in March this year. For his total work, Bill Hamilton was awarded numerous prizes, the most important of which was the Crafoord award of the Royal Swedish Academy of Sciences in 1993, the equivalent of a Nobel Prize in Ecology and Evolutionary Biology.

Bill Hamilton was an excellent naturalist, in particular where insects were concerned. As he once (My intended burial and why) wrote: "There seem to be people incurably fascinated by insects. I am one of them." And, he loved sharing his entomological experiences. At dinner during a meeting in Finland (which I will come back to), I told him about our then recently started programme on Acromyrmex ants. Bill drew out a pencil, asked whether I had a piece of paper, and told me the natural history of what he considered the most remarkable Acromyrmex ant that he had come across while travelling through Amazonia. It is a species that builds a litter nests at the foot of a tree, where the ants are somehow able to withstand (with their fungus garden) frequent flooding.

Bill Hamilton's perception of the living world around him saw genes everywhere, but these were not biochemical genes. In fact, all the way from his student days in Cambridge, he seems to have lacked an interest in molecules. In one of his autobiographical sketches (Narrow Roads of Gene Land, page 12) he wrote: "....still at Cambridge, I had made the decision that I would not even try to come abreast of the important work that was being done around me on the molecular side of genetics. This might well be marvellous in itself: I admitted the DNA story to concern life's most fundamental executive code. But, to me, this wasn't the same as reading life's real plan. I was convinced that none of the DNA stuff was going to help me understand the puzzles raised by my reading of Fisher and Haldane or to fill in the gaps they had left". Instead, the genes in Bill Hamilton's world were abstract ones, ones that could be postulated and hypothesised by the scores and ones that could be shaped into impeccable lines of logic. By the time he wrote his famous inclusive fitness papers, he was sure that he was right, but had to fight journal editors, reviewers and peers who remained unconvinced. In yet another piece of autobiographical text (My intended burial and why) he wrote: "My ideas about kin selection were at last written down and submitted to a journal. I was pretty sure they were right ­ that is, I was sure they were correctly argued. If they were it was clear that no amount of evidence from nature would make them wrong; or, if it did, then at least for my comfort, Darwin's and Fisher's versions of evolution, perhaps along with all of Mendel's genetics, would have to come crashing down as well." Typical for Bill Hamilton's idiosyncratic way of being the extremely proficient scientist he was, was his conviction that: "...the quickest way to understand what puzzled me was to spend more time thinking about what I already knew, not necessarily collecting more data" (Narrow Roads of Gene Land, p. 12).

Bill Hamilton was sometimes criticised for opaque scientific writing and lecturing, but he could certainly give brilliant seminars as well, at least for those in the audience that could appreciate his digressions into details of natural history to drive a hypothesis home. Although especially his early papers are not easy to read, they are densely packed with original ideas, often just hinted at in one or two sentences. In his later years Bill Hamilton came to write beautiful autobiographic prose. His paper "My intended burial and why" - originally in Japanese - has just been republished in English by Ethology, Ecology and Evolution and is highly recommended reading. His book "Narrow roads of gene land" part 1 is a gem that should be on every evolutionary interested biologist's shelf, because of the collection of his early papers that it contains, but first and foremost because of the retrospective introductions that he wrote to each of them. I was told that the second volume, covering Bill Hamilton's later work on parasite hypotheses, was almost complete when he died and will be published shortly.

In his typical modest way, Bill Hamilton distrusted scientific and administrative establishments and did not hesitate to challenge them. Just by the time that most evolutionary biologists had become convinced that the GAIA hypothesis was basically wrong, he came up with a version that had the potential to be at least partially right. Bill Hamilton had a sceptical attitude towards some of the current medical practices and in particular to the medical industry. He saw very clearly that future genetic tinkering with our own species' destination would happen there and he was highly worried that short-term economic interests and lack of basic evolutionary knowledge in these circles could easily make this process go astray and not be in the long term interest of humanity.

About ten years ago, two articles, one published as a working paper of the University of Wollongong and the other in the non-scientific journal Rolling Stone, postulated that human immunodeficiency viruses have entered the human population in the 1950's by hitchhiking (and rapidly evolving) in the ape and monkey tissue cultures that were used to develop low-virulence, live polio virus for large scale oral vaccination programs in Africa. This would imply that the AIDS pandemic is human-caused and that well-intended medical efforts to combat (successfully) a nasty disease, has possibly produced a worse one, because of ignorance about the adaptive potential of unknown viruses in tissues of our close primate relatives. In the early 1990's, Bill Hamilton was one of the very few scientists that took this hypothesis seriously, only to find out that further exploration and testing of this sinister idea of possible and unintended human error was no-go territory in the medical establishment and met with walls of silence among his peers. When contacted somewhat later by the journalist Edward Hooper, who was to devote nearly ten years of his life to thoroughly investigate the pro's and con's of this oral-polio-vaccine (OPV) hypothesis, he wrote out a personal grant to Hooper from his Kyoto prize money and continued to support him intellectually until the project was finished.

The result of Hooper's investigations is a remarkable book "The River", which came out last year. As Bill Hamilton wrote in the foreword:" The thesis of The River is that the closing of ranks against inquiry (by medical researchers and medical industry) may, in this case, be preventing proper discussion of an accident that is bidding to prove itself more expensive in lives than all the human attritions put in motion by Hitler, Stalin, and Pol Pot." The River is a thoroughly researched 858 page historical biogeography of the incidence and spread of HIV 1 and HIV 2. It maps out incredible circumstantial evidence that the infections started in the precise areas where oral polio vaccines were mass administered in the late 1950's. A few essential black boxes remain, however. First, there is no formal proof that kidneys of chimpanzees and macaques and/or sooty mangabeys (the respective hosts of the closest SIV relatives of HIV-1 and HIV-2) were used in tissue cultures to select and multiply the strains of live polio vaccine that were mass fed to African people in those days. Second, there are no currently known "missing links" between the respective SIV's and early HIV's. Hooper's book is especially revealing in how the medical establishment has actively prevented during an entire decade that the few remaining samples of these early polio vaccines were tested for DNA sequences of HIV precursors. Bill Hamilton took an active role in correspondence to have these samples released, throwing in his entire weight as a multi-laureate evolutionary biologist. The field trip to Africa that was to become fatal for him was meant to trace the HIV-1 precursors in faecal samples of chimpanzees in the same Congo populations where hunters were known to have caught these animals for medical tests in the 1950's.

The jury will probably be out for years to decide on the validity of the OPV hypothesis. A first phylogenetic reconstruction of the evolutionary tree of the known HIV-1 strains published just weeks ago (Korber et al., Science, 9 June 2000) indicates an earlier origin (sometime in the 1930's) than inferred by Hooper. However, the debate is fully on and no recent publication in Nature or Science now fails to cite the OPV hypothesis. DNA testing of relevant samples (old ones and new ones collected by Bill Hamilton and his crew in Africa) seems to have begun and a meeting hosted by the British Royal Society this autumn will continue the debate. Even if the OPV hypothesis will ultimately be proved wrong or incomplete the 850+ pages of The River will still document how easily things could have gone wrong in the way hypothesised by Hooper. The debate has already influenced the discussion on the use of xeno-transplanted organs in human medicine, because the risk of introducing highly virulent and incurable viral diseases into the human population are apparently real. Whatever the outcome of these debates, Bill Hamilton's engagement in it at the cost of his own life may well have initiated a tremendous boost to having Darwinian Medicine been taken seriously, a development that has otherwise been slow in coming in spite of ample efforts by evolutionary biologists during the past decade.

Several obituaries of Bill Hamilton have indicated his lack of concern for his personal safety. He faced challenges head on and was willing to take risks for what he considered to be major hypotheses in need of testing or opportunities not to be missed. Several of us here will remember the meeting in Tvärminne, Finland in January 1994. Pekka Pamilo had invited Bill the year before, almost apologising that apart from good science Finland would not have much to offer nature-wise in January. The answer, however, was that that would not matter, because conditions might then be excellent for skating, something he apparently used to do while at Michigan and which he had sorely missed since his return to Britain. Bill arrived at the meeting with a huge suitcase, explaining somewhat embarrassedly that this size had been needed to accommodate his skates. This put the organisers into a nasty dilemma, because the winter had been very mild (for Finnish standards), so that the ice in the Baltic was thin and unreliable. To avert disaster the organisers therefore issued a general statement that nobody should go walking on the ice, at least not before they had given their talk. However, at some point Bill told Pekka that he now had given his talk... Further arguing was to no avail and worried delegates rushed to the windows to watch Bill skate remarkably close to where there was hardly supposed to be any ice and to see Pekka standing worriedly on the beach in case an emergency would arise.

History will ultimately decide on the true significance of Bill Hamilton's work in comparison to the giants of evolutionary biology on whose shoulders he was standing. My personal appreciation is that he may well surpass Haldane and even R. A. Fisher, who inspired so much of his work, when historians of science will make up the accounts, perhaps in the second half of the century that has just started. As Robert Trivers wrote in his obituary in Nature, inclusive fitness theory is the only true advance since Darwin in our understanding of natural selection. What I think should be added to this is that it was in fact Bill Hamilton who started the completion of the Copernican revolution of science by showing that social interactions between any organisms are ultimately shaped by as yet too little known mixes of kin-selection and reciprocity. Bill Hamilton's work has taught us that these forces may occasionally produce brilliant cooperation among individuals and even species, but that understanding will have to be based on selfish replicators within these organisms. A depressing thought of (also human) relativity, not in the least for Bill Hamilton himself (as his autobiographic writings clearly demonstrate), but ­ like the other major steps in scientific understanding ­ a notion that humanity ultimately will have to come to grips with in order to achieve global social systems that are stable in spite of an inherited and internally divided human nature.

Jacobus J. (Koos) Boomsma; Firenze, 8 July 2000