Brief Candle in the Dark Read online

  The dreamlike presence of large tankers deep in the jungle was one of the most vivid memories I took away from the place. On several afternoons I had joined the resident scientists swimming off a raft, and it was a surreal experience to see those gigantic vessels gliding calmly, and surprisingly quietly, through the still, clear water, just a few yards away behind the trees. Some of the women scientists liked to sunbathe, and I couldn’t help wondering what the tanker crews thought about the undraped feminine pulchritude diving off the raft deep in the jungle. If those mariners were Greek, did they think Sirens; or if German, Lorelei? Or – peering through the lush tropical vegetation – did they see a vision of Eve’s innocence before the Fall? They had no way of knowing that these tropic nymphs had PhDs in science from some of the top universities in America.

  I’ve mentioned the apparent territoriality of those busy and dedicated scientists whose island fastness I was briefly allowed to invade, but I mustn’t exaggerate it. I learned from friendly experts most days, either in the field or in the dining room. Elizabeth Royte independently noted the same slight initial froideur in her book about her own visit to Barro Colorado, The Tapir’s Morning Bath. For her, as for me, it thawed later, as she gradually became accepted as an in-group islander and was allowed to help with the research. The first to befriend her was the senior scientist on the island, the delightfully eccentric Egbert Leigh, and he was hospitable to me too. I already knew his name as the author of a thought-provoking paper on ‘The parliament of genes’ and was quite surprised to find this deep-thinking theorist deep in the Central American forest. But there he was, with his family, in the only permanent residence on the island, known as Toad Hall. ‘Toadish’, I later learned, was an epithet of high praise in Dr Leigh’s vocabulary. I never quite discovered what it meant to him: I suspect something multifaceted and subtle, like ‘spin’ in the private vocabulary of the English mathematician G. H. Hardy (a term of approbation, derived in his case from cricket, whose exact meaning C. P. Snow struggled to elucidate in his affectionate memoir of Hardy). Egbert Leigh and I found common ground in our admiration for R. A. Fisher, and he barked out his appreciation in accents best summed up in the phrase (I can’t trace the origin of the witticism) ‘irritable vowel syndrome’.

  If the island housed theoretical firepower in the form of Egbert Leigh, the intellectual armoury was massively afforced again with the arrival of John Maynard Smith, the first half of whose month as visiting consultant overlapped with the second half of mine. John always was a man eager to learn as well as teach, and it was wonderful to walk the jungle trails in his company and learn biology from him – as well as learn from him how to learn from the local experts who conducted us. I treasure an aside from him about one young man who was walking us through his research area: ‘What a treat it is to listen to a man who really loves his animals.’ The ‘animals’ in this case were palm trees – but that was John all over, and one of the reasons I loved him. And miss him.

  Among the actual animals, as opposed to photosynthetic honorary animals, were the well-named spider monkeys, with their splendid fifth limb in the form of the prehensile tail. And the howler monkeys, with their bone-amplified voice boxes, whose travelling waves of crescendos and decrescendos could easily be mistaken for a squadron of jet fighters roaring through the canopy. On one occasion I encountered a full-grown tapir, close enough to see the ticks on its neck, engorged with its blood. It was hard to walk a day in the jungle without picking up one’s own cargo of ticks. But they were always small when they first hitched a ride, and everyone carried a roll of sticky tape to peel them off. Tapirs, by the way, seem never to have occurred in Africa, so it was a bit of a solecism for Stanley Kubrick to portray them as hunted by our hominin ancestors at the beginning of that magnificent film 2001: A Space Odyssey.

  Insofar as I got any constructive work done during my time in Panama, it took the form of writing chapters of The Extended Phenotype, and in this I was helped by discussions with some of the scientists on the island. From the dates, I know that I spent Christmas 1980 on the island but I remember nothing about it, which suggests that not a lot of fuss was made of the occasion. I do recall some kind of a party with a cabaret, which may have been associated with Christmas; Ragavendra Gadagkar was co-opted to act as Master of Ceremonies, somewhat to his bemusement I think, as he had only just arrived.

  I discovered a special affinity for the leaf-cutter ants, introduced to me by Allen Herre along with the more sinister army ants, who one night invaded a bathroom and linked limbs to hang in there, festooned like noisome brown-black curtains. Allen was not the only regular who earnestly warned me about the giant ponerine ants, Paraponera, whose formidable sting placed them among the most talked-about denizens of the jungle. My fear-primed eyes saw them often, and I kept my distance with the utmost respect.

  I found the leaf-cutter ants more appealing and would stand for what seemed like hours watching the flowing green torrents of walking leaves: tens of thousands of workers, each with its verdant parasol held aloft en route for the dark, subterranean fungus gardens. I was filled with naive fascination that they were cutting leaves not to slake their own taste for greenery, either now or later, but to make compost on which to grow fungi which would eventually be eaten by others in their teeming colony after they themselves had died. Were they motivated by some myrmecine equivalent of an ‘appetite’, which was satisfied not by a full stomach but by, say, the feel of a leaf in the jaws, or something even more indirect? I didn’t need John Maynard Smith to remind me that natural selection favours ‘strategies’ which are not assumed to be understood by the animals that act them out. It is not for us to say whether ants feel any conscious appetites or desires, wants or hungers. I felt a glow of understanding, which was repeated in an encounter with the army ants, later described in my third book, The Blind Watchmaker. I explained that, as a child in Africa, I had been more afraid of driver ants than of lions or crocodiles; but I quoted E. O. Wilson to the effect that a driver ant colony is ‘an object less of menace than of strangeness and wonder, the culmination of an evolutionary story as different from that of mammals as it is possible to conceive in this world’. And I continued:

  As an adult in Panama I have stepped aside and contemplated the New World equivalent of the driver ants that I had feared as a child in Africa, flowing by me like a crackling river, and I can testify to the strangeness and wonder. Hour after hour the legions marched past, walking as much over each others’ bodies as over the ground, while I waited for the queen. Finally she came, and hers was an awesome1 presence. It was impossible to see her body. She appeared only as a moving wave of worker frenzy, a boiling peristaltic ball of ants with linked arms. She was somewhere in the middle of the seething ball of workers, while all around it the massed ranks of soldiers faced threateningly outwards with jaws agape, every one prepared to kill and to die in defence of the queen. Forgive my curiosity to see her: I prodded the ball of workers with a long stick, in a vain attempt to flush out the queen. Instantly 20 soldiers buried their massively muscled pincers in my stick, possibly never to let go, while dozens more swarmed up the stick causing me to let go with alacrity.

  I never did glimpse the queen, but somewhere inside that boiling ball she was, the central data bank, the repository of the master DNA of the whole colony. Those gaping soldiers were prepared to die for the queen, not because they loved their mother, not because they had been drilled in the ideals of patriotism, but simply because their brains and their jaws were built by genes stamped from the master die carried in the queen herself. They behaved like brave soldiers because they had inherited the genes of a long line of ancestral queens whose lives, and whose genes, had been saved by soldiers as brave as themselves. My soldiers had inherited the same genes from the present queen as those old soldiers had inherited from the ancestral queens. My soldiers were guarding the master copies of the very instructions that made them do the guarding. They were guarding the wisdom of their ancestors, th
e Ark of the Covenant . . .

  I felt the strangeness then, and the wonder, not unmixed with revivals of half-forgotten fears, but transfigured and enhanced by a mature understanding, which I had lacked as a child in Africa, of what the whole performance was for. Enhanced, too, by the knowledge that this story of the legions had reached the same evolutionary culmination not once but twice. These were not the driver ants of my childhood nightmares, however similar they might be, but remote, New World cousins. They were doing the same thing as the driver ants, and for the same reasons. It was night now and I turned for home, an awestruck child again, but joyful in the new world of understanding that had supplanted the dark, African fears.

  I made a half-hearted attempt at some quantitative observations on the leaf-cutter ants, but I never really got anywhere; there wasn’t enough time. And I fear I am not very good at getting down to properly planned research with a specified end. I can do ‘pilot experiments’, flitting like a butterfly as the interest takes me, but to do real research you have to write down the time course of the project in advance and adhere to it rigorously. Otherwise it’s too easy to stop when you have the result you want – and that, if not quite deliberate cheating, has been a serious source of error in the history of science.

  I spent much of a day watching, in horrified fascination, a clash between two rival colonies of leaf-cutters, which made me think of the First World War. The large battlefield became littered with limbs, heads and abdomens. I hoped, and half believed, that the ants didn’t feel pain or fear. They were acting out genetically programmed automatisms, wound up like clockwork in their tiny brains – Maynard Smithian ‘strategies’ – but that doesn’t in itself mean they didn’t feel pain. I’d be pretty surprised if they did, but I can imagine no way of deciding the question.

  The mind of an academic needs refreshing by such an interlude as mine in Panama with dear JMS, and when I returned to everyday life in Oxford it seemed just that little bit less everyday.

  GO TO THE WASP, THOU SLUGGARD

  EVOLUTIONARY ECONOMICS

  NATURAL selection is a miserly economist, invisibly counting the pennies, the nuances of cost and benefit too subtle for us, the observing scientists, to notice. Human economists weigh up rival ‘utility functions’, alternative quantities that an agent, such as a person or a firm or a government, might choose to maximize: gross national product; personal income; personal wealth; company profits; the sum of human happiness. None of these utility functions is ‘correct’ to the exclusion of others. Nor is there any one correct agent. You can choose any utility function you like and attribute it to any agent you like, and you’ll get the appropriate, but different, result.

  Natural selection isn’t like that. Natural selection maximizes only one ‘utility’: gene survival. If you personify a gene as a metaphorical ‘agent’ doing the maximizing you’ll get the right answer. But in practice genes don’t directly behave as agents, so we shift our gaze to the level at which decisions are actually taken: usually the individual organism which, unlike a gene, has sense organs to apprehend the world, memories to store past events, computational apparatus in a brain to take decisions from moment to moment, and muscles to execute them.

  Why, by the way, do biologists find it helpful to personify at all, whether with genes or individuals, to view them as ‘agents’? I suspect it’s because we are an intensely social species, social fish swimming through a sea of people. So much of what happens in our environment is caused by the deliberate actions of persons: how natural, then, to generalize to inanimate ‘agents’. One way this inclination manifests itself is as superstition – fear of poltergeists or spirits – and that’s the downside. But the upside is that scientists, so long as they know what they are doing, can use a legitimate personification as a handy and congenial short cut to getting their sums right. I once heard the Nobel Prize-winning biologist Jacques Monod make a remark that has stayed with me for its imaginative colour: ‘When faced with a chemical problem of this kind, I ask myself, what would I do in this situation if I were an electron?’ Physicists can explain refraction by personifying photons, adjusting their angle to minimize their travel time through media that slow them down to different extents. A photon is like a lifesaver on a beach, optimizing his trajectory towards a drowning swimmer, off to one side of the beach. He runs (fast) most of the way along the beach, then bends his angle to swim (inevitably more slowly), choosing his two angles to minimize his total travel time. When photons move from air (fast travel) to glass (slower), you’ll correctly calculate the angle of refraction if you assume that they behave like agents, although not consciously calculating like the lifeguard. A stone tossed through the air follows a trajectory as if it’s ‘trying’ to minimize a mathematical quantity that physicists can calculate. In a chemical reaction you get the right answer if you assume that the reactants are ‘trying’ to maximize another mathematical quantity called ‘entropy’. Of course, nobody thinks these inanimate entities are really trying to do anything. It’s just that you get your sums right if you fancy that they are, and the human mind is geared to think in terms of purposeful agents.

  So, biologists shift the focus of our legitimate personification from gene to individual organism. We leave open the question of whether the organism is a conscious agent. We know the gene isn’t. The organism takes decisions calculated (unconsciously is all we need to assume) to maximize the long-term survival of the genes that ride inside it – the genes that programmed, via embryonic development, the nervous system that makes the decisions. The decisions give every appearance of being those of a shrewd economist, acting as if deploying (distributing, eking out) limited resources in the service of passing genes on to future generations. The limited resources of a potato plant flow in from the sun, the air and the soil. The shrewd economist which is the plant has to ‘decide’ how to apportion those resources between tubers (storage for the future), leaves (solar panels to gather more sunlight to turn into chemical energy), roots (to suck up water and minerals), flowers (to attract pollinating insects with costly nectar to pay them), stems (to hold the leaves aloft to the sun) and so on. Allocating too generously to one sector of the economy (say, the roots) and too meanly to another (say, the leaves or flowers) will result in a less successful plant than a perfectly balanced distribution to all the departments of the plant’s economy.

  Every decision that an animal takes, whether behavioural (when to tug on which muscle) or developmental (which bits of the body to grow bigger than others), is an economic decision, a choice about the allocation of limited resources among competing demands. So are decisions on how much of the time budget to allocate to feeding, how much to subduing rivals, how much to courting a mate and so on. So are decisions on parenting (how much of the limited budget of food, time and risk to spend on the present child and how much to hold back for future children). So are decisions on life history (how much of life should be spent as a caterpillar, growing by feeding on plants, and how much as a butterfly, sipping aviation fuel from the nectaries of flowers while pursuing a mate). It’s economics everywhere you look: unconscious calculations, ‘as if’ deliberately weighing up the costs and benefits.

  That’s all theory and a bit hand-wavery. Can we go out and record the moment-to-moment behaviour of animals in the wild and calculate their time budgets as examples of their economic decisions? Yes, we can; but it requires more or less continuous observation of individually marked animals, in their natural environment. And it can only be done by a skilled and meticulous observer, with huge reserves of patience, persistence, intelligence and dedication. Allow me to introduce Dr Jane Brockmann.

  I met Jane when she bounced cheerily into my office in Oxford in the summer of 1977. She had been accepted by my colleague and boss, Niko Tinbergen’s successor, the idiosyncratically brilliant David McFarland, to do a post-doc. As things turned out, her arrival was delayed a year, by which time David had gone on sabbatical leave, so Jane, by default, worked with me, his depu
ty. I came to think it a most fortunate happenstance for me, and I like to think that Jane, too, did not regret it.

  Jane’s PhD at the University of Wisconsin was on the great golden digger wasp, Sphex ichneumoneus. She came to Oxford bearing large quantities of meticulously systematic observations of the behaviour of individually marked female wasps in two different field sites, in New Hampshire and Michigan, and it was on these measurements – originally made for a quite different purpose, more related to David McFarland’s field than to mine – that we ended up working together.

  Not all wasps are social, like the familiar striped vespids known to Americans as yellowjackets, and to all of us as jam-loving spoilers of teatime in the garden. Many wasp species are solitary, and Sphex is among them. Female digger wasps, once mated, do all the work on their own, with no workers to help. Males disappear after mating, leaving the females holding the babies. Well, not literally holding. The typical cycle is as follows. The female digs a burrow about six inches deep, slightly angled from the vertical and terminating in a short side tunnel leading to a widened chamber. She then sallies forth in search of prey, which for this species of digger wasp consists of katydids (elegant, usually green, long-horned grasshoppers). She catches a katydid, stings it to paralyse but not kill it, flies home with it, then drags it down the burrow into the chamber. She repeats this several times until she’s amassed a tidy pile of up to half a dozen katydids in the burrow, then lays an egg on top of the pile. She sometimes then excavates another side chamber elsewhere in the same burrow and repeats the process with fresh katydids. Finally she seals up the burrow, and proceeds to do the same with a new burrow. Some digger wasp species pick up a small stone in their jaws and use it as a hammer to tamp down the soil – a feat which has been dramatically hailed as tool use, once thought a human monopoly. When an egg hatches inside its secure, dark chamber, the larva feeds on the paralysed katydids, fattens on their nourishment, and eventually pupates and emerges as an adult wasp of the next generation, male or female.