With his Amish-style beard and Bostonian vowels, his West Coast address but East Coast manners, Jared Diamond is a hard man to place. Magazine readers know him as an erudite but entertaining ecologist, an expert on the birds of New Guinea, who writes accessibly about ecology, evolution and conservation. But there is another Jared Diamond, a professor of physiology at the University of California Medical School in Los Angeles. This Jared Diamond lists an impressive string of publications with titles such as ‘Adaptive changes in ileal mucosal nutrient transport following colectomy and endorectal ileal pull-through with ileal reservoir’.
The two are, of course, one person, who is well regarded in both his fields. Professor Ian Glynn, head of the Physiological Laboratory at the University of Cambridge, says Diamond’s early work on the movement of water across membranes was ‘extremely influential’. And Bob May, an ecologist and Royal Society professor at the University of Oxford, says that Diamond has made ‘significant scholarly contributions to the subject’. May singles out the empirical rules Diamond devised after much practical observation of Pacific islands, rules that describe which species tend to settle first on islands and which tend to go extinct first.
Nevertheless, Diamond’s two sides have been separate for most of his career. ‘Until several years ago,’ he told me in a recent conversation. ‘I was functioning essentially as a split brain with no connection at all between the two fields.’ Colleagues in both fields were surprised about the other. ‘My physiology friends by and large really don’t understand the point of the work on birds. While my friends in ecology really don’t understand the point of the work in physiology.’
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He has bridged that chasm now from both directions. On the physiology side, Diamond started to feel a growing dissatisfaction with the whole approach of molecular biologists: ‘The questions they ask are essentially descriptive. They don’t ask ultimate questions – why natural selection results in molecular biology being this way rather than some other way.’ As an ecologist, he knows that humanity is threatening its own future. ‘We are exterminating species,’ he says, ‘but we depend on many species for our own life support. I don’t know whether we’re going to be left with 20 or 90 per cent of our current quota of species by the latter part of the next century. It’s a toss up.’
That realisation was brought to a head four years ago with the birth of Diamond’s twin sons. ‘Before, it was in a way an academic issue. But I now have a concrete investment in what’s going to happen in the middle of the next century.’
The most tangible outcome of Diamond’s concern is his book, The Rise and Fall of the Third Chimpanzee, published this year. In it, he first explores what he calls humanity’s animal heritage – the unbelievably small distance, in genetic terms, between ourselves and the other two chimpanzees, the pygmy and the now somewhat ironically named common chimpanzee. ‘Humans,’ Diamond writes, ‘do not constitute a distinct family, nor even a distinct genus, but belong in the same genus as common and pygmy chimps.’ He goes on to explore the larger differences in life cycle, and the immense chasm of culture that separates us from the other chimpanzees. Along the way he surveys our uniquely human characteristics, and especially our historic capacity for self-destruction.
Central to Diamond’s thesis is the genetic closeness of the three chimpanzees, a relationship far closer than their names would suggest. Pygmy and common chimps are two species of a single genus, Pan, members of a different family from our own genus, Homo. Other animals that share a single genus – such as the red-eyed and white-eyed vireos, the willow warbler and the chiffchaff, the various species of gibbon – are much further apart genetically than ourselves and the chimps. On this basis, argues Diamond, ‘there are not one but three species of genus Homo on Earth today: the common chimpanzee, Homo troglodytes; the pygmy chimpanzee, Homo paniscus; and the third chimpanzee or human chimpanzee, Homo sapiens’.
This perception, while not exactly novel, has forced Diamond to scrutinise his own attitude to research on chimpanzees. ‘I don’t see any (lethal) medical research on chimpanzees that really justifies the ethical problems,’ he says. But he is quick to qualify this: ‘If you’re going to object to research on chimps then you have to ask, ‘Where do you draw the line? Why don’t I also object to research on monkeys?’. It bothers me, but not as much.’
The distinction is not simply one of genetic identity. He recalls, for example, how, long before he knew anything at all about genetic distances, he was disturbed by the first research chimpanzee he ever saw. It was sitting alone in an empty indoor cage at the United States National Institutes of ÎçÒ¹¸£Àû1000¼¯ºÏ, where it had been injected with a slow virus and was, as Diamond put it, ‘waiting to die’. More than mere genetic closeness, he worries about the ethical implications of chimpanzees’ social relationships, and the extent of their feelings.
Shortly before we talked, Diamond had returned from a visit to the Language Research Center at Georgia State University, where Duane Rumbaugh and his colleagues continue to teach chimpanzees to communicate using symbols. A chimpanzee with its trainer wandered by outside, carrying a portable ‘keyboard’, a piece of cardboard with about 50 symbols on it. As they passed Rumbaugh’s window, the chimpanzee pointed out – on the keyboard – that it would like a surprise. The trainer duly brought it round to meet the surprising, and surprised, Diamond.
Diamond told how the young pygmy chimpanzees, who have to take a nap in the afternoon, insisted that their trainer lie down with them ‘just like my own kids’. How they asked to use the potty. How they could understand complicated sentences. When pressed on the ethical implications of these stories, he conceded: ‘That’s a longwinded way of saying that that sort of cognitive ability – regardless of the genes involved – is just so close to us that one has to feel uncomfortable’ about using chimpanzees in biomedical research.
Then he went further: ‘Exactly why do we do experiments on healthy chimpanzees, on intelligent, socially capable chimpanzees, when we would be utterly disgusted at the thought of doing experiments on mentally retarded people, some of whom have considerably less mental capacity than the chimp, much less capacity for social relationships and a dimmed capacity for language?’ He continued: ‘There is nothing we can say in defence, except that we arbitrarily say that it’s OK.’
Diamond’s own medical career began early, with summer jobs in various laboratories of Harvard Medical School, where his father taught. From the first, he says, he wanted to be a doctor, ‘like Dad’. Gradually, however, his goal changed, and instead of following his father to Harvard Medical School he went to England, to the University of Cambridge, to do a PhD in physiology.
But medical research was always only part of Diamond’s life. As an undergraduate, he and a classmate went mountain climbing in Peru, and on the way back decided to stop off for a spot of bird watching in the Amazon. The result: Diamond became hooked on tropical birds. Without abandoning his medical research, Diamond left it sufficiently often to become a world authority on the birds of New Guinea, which he has visited on and off for the past 25 years. He has conducted ecological surveys, tapped the encyclopedic knowledge of the local people, and helped governments to situate their national parks in the richest areas. He also rediscovered a bird long since thought to have vanished, the golden fronted bowerbird.
This enigmatic bird has a chequered history. Only four specimens are known, and they turned up in 1895 at a Paris feather merchant’s, their gorgeous golden plumes destined for ladies’ hats. Lord Rothschild had standing orders for any interesting specimens to be saved for him, and duly bought all four for his museum at Tring, but nobody knew where exactly the birds had been caught, or whether there were any more. After that, nothing more was heard of the bird. Various expeditions were mounted to find it, and all failed. It was, Diamond says, ‘the dream goal of New Guinea ornithologists’. His turn came in 1979, when the Indonesian government asked him to survey an area of the Foja mountains, too far from the coast to walk to and hence uninhabited by New Guineans and unvisited by biologists.
On his second visit, a helicopter dropped Diamond and his Indonesian colleague in a clearing. ‘When I walked into the forest, having been dropped off by helicopter, the first bird I saw was the bowerbird.’ It was the plumage that gave it away. ‘The crest is exceptionally long,’ he explained, ‘and covers the entire forehead, and it’s a glorious golden yellow orange colour.’ That first afternoon he found the bower. On the second day, he found the mating ground, and sat watching the birds, who were completely unafraid of humans.
Although he made important behavioural observations, including tape recordings, Diamond did not get the one record everyone wanted, a photograph. On his early trips he had taken thousands of pictures, but then a mould attacked his equipment and pictures. ‘I was just shattered, and I gave up the camera and did not pick it up again until the mid-1980s.’
Diamond’s personal history does more than hint at the way his career developed. His father is a renowned paediatrician, well known in medical circles for developing the technique of exchange transfusion in newborn infants, a life-saver when mother and child have incompatible blood groups. His mother was a natural-born linguist, and Diamond has inherited some of her talent. He studied Latin, Greek, French, German and Russian at school or college, then others on his travels. New Guinea, however, is a linguist’s dream – or nightmare. ‘Every month, as I changed sites I would get to a new language,’ Diamond says. He learnt just one, Fore; the rest of the time he gets by with Pidgin in Papua New Guinea and Indonesian in Irian Jaya.
Over the years, Diamond says, his two lives have moved closer to one another. His medical interests, for example, are shifting away from pure membrane physiology and towards a more evolutionary view of the design of the digestive tract. What, for example, is the reserve capacity of the digestive system? It should be able to cope with extra loads, say a meal particularly rich in protein, without wasting energy on making more of some enzyme than might reasonably be needed. So far, he has found that many digestive enzymes look as if they are able to cope with about double their average load. That could prove important in tackling diseases of modern life, such as adult-onset diabetes.
His ornithology and ecology have become more practical too. In addition to surveying and listing birds, he is putting the information to use designing national parks. And he is doing more popular science writing of the kind that went into The Third Chimpanzee. ‘Science is important to the modern world,’ he says, and people have a right to be told what their taxes are paying for. ‘But scientists by and large are not interested and not well trained to communicate their ideas to the public. Often there’s a widespread attitude that anyone who does try to convey science to the public is doing it as watered-down gruel. They obviously can’t be any good at scientific research if they’re going into this secondary thing.’
The combination of medicine, evolutionary biology, ecology and linguistic ability has offered Diamond a special outlook on the world. He knows, for example, that many human differences stem from genetic differences, an idea that is surprisingly controversial in the US. Digestive physiology, his speciality, offers a classic example. After the Second World War, the US shipped vast quantities of dried milk around the globe to help to combat starvation. Reports kept coming back that people who drank the milk became sick. ‘Our reaction,’ says Diamond, ‘was, ‘Oh those sillies, they must be using dirty water, they don’t know how to make it up properly.’ ‘ It took a decade to realise that many adults (most adults, in fact) are genetically unable to digest milk properly.
Equally, Diamond is adamant that cultural diversity has no basis in genes. ‘When I started out in New Guinea in 1964 many of the New Guineans I worked with were five years out of the Stone Age. One of them had participated in the last tribal massacre. And yet when I go back New Guineans today are piloting their own jet airplanes. It’s obvious that the differences are cultural (not genetic).’
The third thing Diamond stresses is that human culture as we know it is a very new property of our species, probably less than 40 000 years old. In his opinion what enabled the growth of culture was the growth of our ancestors’ ability to talk. Language, he says, was the key to a development he calls ‘The Great Leap Forward’. Echoes of Mao’s revolution are deliberate: ‘Sure it has negative overtones. We know what happened to the Chinese Great Leap Forward. We don’t yet know whether there is a time bomb built into our own Great Leap Forward.’
The key problem, says Diamond, is overpopulation. He reminds his readers that ‘we already appropriate about 40 per cent of the Earth’s net productivity (that is, the net energy captured from sunlight). With the world’s human population now doubling every 41 years, we will soon have reached the biological limit to growth, at which point we will have to start fighting each other in deadly earnest for a slice of the world’s fixed pie of resources.’ But again, the biological view of humanity colours his prescription. The rhythm method, for example, elicits the closest Diamond comes to scorn: ‘For gorillas, terrific. For gibbons, superb. But human physiology was designed for the rhythm method not to work. One could say that in an anthropomorphic sense, one of the goals of evolution in redesigning human reproductive physiology was to frustrate the rhythm method, since sex has become divorced from reproduction.’
The core of Diamond’s philosophy is that humans are animals, with genetic predispositions shaped by millions of years of evolution. But he also sees us as cultural animals, whose ability to understand the past and adapt frees us from our genetic heritage.’ The most important missing ingredient for dealing with our environmental problems is simply political will,’ he says, not technical innovation. ‘My hope would be that by understanding our history and how often we have made the same type of mistakes, and appreciating that the mistakes have been fatal for some past societies, that we can finally learn from out past and stop repeating it.’
Jeremy Cherfas is a contributing correspondent to Science.
