Arms Races and 'Evolutionary Theodicy'

This article is an excerpt from Chapter 12 of The Greatest Show on Earth (2009)

THE SOLAR ECONOMY

The natural economy is solar-powered. Photons from the sun rain down upon the entire daytime surface of the planet. Many photons do nothing more useful than heat up a rock or a sandy beach. A few find their way into an eye – yours, or mine, or the compound eye of a shrimp or the parabolic reflector eye of a scallop. Some may happen to fall on a solar panel – either a man-made one like those that, in a fit of green zeal, I have just installed on my roof to heat the bathwater, or a green leaf, which is nature’s solar panel. Plants use solar energy to drive ‘uphill’ chemical syntheses, manufacturing organic fuels, primarily sugars. ‘Uphill’ means that the synthesis of sugar needs energy to drive it; by the same token, the sugar can later be ‘burned’ in a ‘downhill’ reaction that releases (a fraction of) the energy again to do useful work, for example muscular work, or the work of building a great tree trunk. The ‘downhill’ and ‘uphill’ analogy is with water flowing downhill from a high tank and driving water wheels to do useful work; or being energetically pumped uphill into the high tank, so that it can later be used to drive water wheels when it flows downhill again. At every stage of the energy economy, whether uphill or downhill, some energy is lost – no energy transaction is ever perfectly efficient. That is why patent offices don’t need even to look at designs for perpetual motion machines: they are implacably and forever impossible. You can’t use the downhill energy from a water wheel to pump the same amount of water uphill again so that it can drive the water wheel. There must always be some energy fed in from outside to compensate for the wastage – and that is where the sun comes in. I’ll return to this important theme in Chapter 13.

Much of the land surface of the Earth is covered by green leaves, which constitute a many-layered catchment for photons. If a photon is not caught by one leaf, it has a good chance of being caught by the one below. In a dense forest, not many photons make it to the ground uncaught, which is exactly why mature forests are such dark places in which to walk. Most of the photons that constitute our planet’s minute share of the sun’s rays hit water, and the surface layers of the sea swarm with single-celled green plants to catch them. Whether at sea or on land, the chemical process that traps photons and uses them to drive ‘uphill’ energy-consuming chemical reactions, manufacturing convenient energy-storage molecules such as sugars and starch, is called photosynthesis. It was invented, more than a billion years ago, by bacteria; and green bacteria still underlie most photosynthesis. I can say this because the chloroplasts – tiny green photosynthetic engines that actually do the business of photosynthesis in all leaves – are themselves the direct descendants of green bacteria. Indeed, since they still autonomously reproduce themselves after the manner of bacteria, within plant cells, we can justly say that they still are bacteria, albeit heavily dependent on the leaves that house them and to which they give their colour. It appears that originally free-living green bacteria were hijacked into plant cells, where they eventually evolved into what we now call chloroplasts.

And it is a neatly symmetrical fact that, just as the uphill chemistry of life is mostly taken care of by green bacteria thriving inside plant cells, so too the downhill chemistry of metabolism – the slow burning of sugars and other fuels to release energy in cells of both animals and plants – is the special expertise of another class of bacteria, once free-living but now reproducing themselves in larger cells, where they are known as mitochondria. Mitochondria and chloroplasts, descended from different kinds of bacteria, each built up their complementary chemical wizardries billions of years before the existence of any living organism visible to the naked eye. Both were later shanghaied for their chemical skills, and today they multiply inside the liquid interiors of the much larger and more complicated cells of creatures big enough for us to see and touch – plant cells in the case of chloroplasts, plant and animal cells in the case of mitochondria.

The solar energy captured by chloroplasts in plants lies at the base of complicated food chains, in which the energy passes from plants through herbivores, which may be insects, through carnivores, which may be insects or insectivores as well as wolves and leopards, through scavengers such as vultures and dung beetles, and eventually to agents of decay such as fungi and bacteria. At every stage of these food chains, some of the energy is wasted as heat as it passes through, while some of it is used to drive biological processes such as muscle contraction. No new energy is added after the initial input from the sun. With a few interesting but minor exceptions such as the denizens of deep ocean ‘smokers’ whose energy comes from volcanic sources, all the energy that drives life comes ultimately from sunlight, trapped by plants.

Look at a single tall tree standing proud in the middle of an open area. Why is it so tall? Not to be closer to the sun! That long trunk could be shortened until the crown of the tree was splayed out over the ground, with no loss in photons and huge savings in cost. So why go to all that expense of pushing the crown of the tree up towards the sky? The answer eludes us until we realize that the natural habitat of such a tree is a forest. Trees are tall to overtop rival trees – of the same and other species. Don’t be misled when you see a tree in an open field or garden that has leafy branches all the way down to the ground. It has that well-rounded shape so beloved of sergeant instructors because it is in an open field or garden. You are seeing it out of its natural habitat, which is a dense forest. The natural shape of a forest tree is tall and bare-trunked, with most of the branches and leaves near the top – in the canopy which bears the brunt of the photon rain. And now, here’s an odd thought. If only all the trees in the forest could come to some agreement – like a trades union restrictive practice – to grow no higher than, say, 10 feet, every one would benefit. The entire community – the entire ecosystem – could gain from the savings in wood, and energy, which are consumed in building up those towering and costly trunks.

The difficulty of cultivating such agreements of mutual restraint is well known, even in human affairs where we can potentially deploy the gift of foresight. A familiar example is a suggested agreement to sit, rather than stand, when watching a spectacle such as a horse race. If everybody sat, tall people would still get a better view than short people, just as they would if everybody stood, but with the advantage that sitting is more comfortable for everybody. The problems start when one short person sitting behind a tall person stands, to get a better view. Immediately, the person sitting behind him stands, in order to see anything at all. A wave of standing sweeps around the field, until everybody is standing. In the end, everybody is worse off than they would be if they had all stayed sitting.

In a typical mature forest, the canopy can be thought of as an aerial meadow, just like a rolling grassland prairie, but raised on stilts. The canopy is gathering solar energy at much the same rate as a grassland prairie would. But a substantial proportion of the energy is ‘wasted’ by being fed straight into the stilts, which do nothing more useful than loft the ‘meadow’ high in the air, where it picks up exactly the same harvest of photons as it would – at far lower cost – if it were laid flat on the ground.

And this brings us face to face with the difference between a designed economy and an evolutionary economy. In a designed economy there would be no trees, or certainly no very tall trees: no forests, no canopy. Trees are a waste. Trees are extravagant. Tree trunks are standing monuments to futile competition – futile if we think in terms of a planned economy. But the natural economy is not planned. Individual plants compete with other plants, of the same and other species, and the result is that they grow taller and taller, far taller than any planner would recommend. Not indefinitely taller, however. There comes a point when growing another foot taller, although it confers a competitive advantage, costs so much that the individual tree doing it actually ends up worse off than its rivals that forgo the extra foot. It is the balance of costs and benefits to the individual trees that finally determines the height to which trees are pressed to grow, not the benefits that a rational planner could calculate for the trees as a group. And of course the balance ends up at a different maximum in different forests. The Pacific Coast redwoods (see them before you die) have probably never been exceeded.

Imagine the fate of a hypothetical forest – let’s call it the Forest of Friendship – in which, by some mysterious concordat, all the trees have somehow managed to achieve the desirable aim of lowering the entire canopy to 10 feet. The canopy looks just like any other forest canopy except that it is only 10 feet high instead of 100 feet. From the point of view of a planned economy, the Forest of Friendship is more efficient as a forest than the tall forests with which we are familiar, because resources are not put into producing massive trunks that have no purpose apart from competing with other trees.

But now, suppose one mutant tree were to spring up in the middle of the Forest of Friendship. This rogue tree grows marginally taller than the ‘agreed’ norm of 10 feet. Immediately, this mutant secures a competitive advantage. Admittedly, it has to pay the cost of the extra length of trunk. But it is more than compensated, as long as all other trees obey the self- denying ordinance, because the extra photons gathered more than pay the extra cost of lengthening the trunk. Natural selection therefore favours the genetic tendency to break out of the self-denying ordinance and grow a bit taller, say to 11 feet. As the generations go by, more and more trees break the embargo on height. When, finally, all the trees in the forest are 11 feet tall, they are all worse off than they were before: all are paying the cost of growing the extra foot. But they are not getting any extra photons for their trouble. And now natural selection favours any mutant tendency to grow to, say 12 feet. And so the trees go on getting taller and taller. Will this futile climb towards the sun ever come to an end? Why not trees a mile high, why not Jack’s beanstalk? The limit is set at the height where the marginal cost of growing another foot outweighs the gain in photons from growing that extra foot.

We are talking individual costs and benefits throughout this argument. The forest would look very different if its economy had been designed for the benefit of the forest as a whole. In fact, what we actually see is a forest in which each tree species evolved through natural selection favouring individual trees that out-competed rival individual trees, whether of their own or another species. Everything about trees is compatible with the view that they were not designed – unless, of course, they were designed to supply us with timber, or to delight our eyes and flatter our cameras in the New England Fall. And history is not short of those who would believe just that, so let’s turn to a parallel case, where the benefits to humanity are harder to allege: the arms race between hunters and hunted.

RUNNING TO STAY IN THE SAME PLACE

The five fastest runners among mammal species are the cheetah, the pronghorn (often called ‘antelope’ in America although it is not closely related to the ‘true’ antelopes of Africa), the gnu (or wildebeest, a true antelope although it doesn’t look much like the others), the lion, and the Thomson’s gazelle (another true antelope, which really does look like a standard antelope, a small one). Note that these top-ranked runners are a mixture of hunted and hunters, and my point is that this is no accident.

Cheetahs are said to be capable of accelerating from 0 to 60 mph in three seconds, which is right up there with a Ferrari, a Porsche or a Tesla. Lions, too, have formidable acceleration, even better than gazelles, who have more stamina and the ability to jink. Cats generally are built for sprinting, and springing on prey taken unawares; dogs, such as the Cape hunting dog or the wolf, for endurance, for wearing down their prey. Gazelles and other antelopes have to cope with both types of predator, and they perhaps have to compromise. Their acceleration is not quite so good as a big cat’s, but their endurance is better. By jinking, a Tommy can sometimes throw a cheetah off its stride, thereby postponing matters until the cheetah has gone beyond its maximum acceleration phase into the exhausted phase, where its poor stamina starts to count. Successful cheetah hunts usually end soon after they start, the cheetah relying on surprise and acceleration. Unsuccessful cheetah hunts also end early, with the cheetah giving up to save energy when its initial sprint fails. All cheetah hunts, in other words, are brief!

Never mind the details of top speeds and accelerations, stamina and jinking, surprise and sustained pursuit. The salient fact is that the fastest animals include both those that hunt and those that are hunted. Natural selection drives predator species to become ever better at catching prey, and it simultaneously drives prey species to become ever better at escaping them. Predators and prey are engaged in an evolutionary arms race, run in evolutionary time. The result has been a steady escalation in the quantity of economic resources that animals, on both sides, spend on the arms race, at the expense of other departments of their bodily economy. Hunters and hunted alike get steadily better equipped to outrun (surprise, outwit, etc.) the other side. But improved equipment to outrun doesn’t obviously translate into improved success in outrunning – for the simple reason that the other side in the arms race is upgrading its equipment too: that is the hallmark of an arms race. You could say, as the Red Queen said to Alice, that they have to run as fast as they can just to stay in the same place.

Darwin was well aware of evolutionary arms races, although he didn’t use the phrase. My colleague John Krebs and I published a paper on the subject in 1979, in which we attributed the phrase ‘armament race’ to the British biologist Hugh Cott. Perhaps significantly, Cott published his book, Adaptive Coloration in Animals, in 1940, in the depths of the Second World War:

Before asserting that the deceptive appearance of a grasshopper or butterfly is unnecessarily detailed, we must first ascertain what are the powers of perception and discrimination of the insects’ natural enemies. Not to do so is like asserting that the armour of a battle-cruiser is too heavy, or the range of her guns too great, without inquiring into the nature and effectiveness of the enemy’s armament. The fact is that in the primeval struggle of the jungle, as in the refinements of civilized warfare, we see in progress a great evolutionary armament race – whose results, for defence, are manifested in such devices as speed, alertness, armour, spinescence, burrowing habits, nocturnal habits, poisonous secretions, nauseous taste, and procryptic, aposematic, and mimetic coloration; and for offence, in such counter-attributes as speed, surprise, ambush, allurement, visual acuity, claws, teeth, stings, poison fangs, and anticryptic and alluring coloration. Just as greater speed in the pursued has developed in relation to increased speed in the pursuer; or defensive armour in relation to aggressive weapons; so the perfection of concealing devices has evolved in response to increased powers of perception.

Note that the arms race is run in evolutionary time. It is not to be confused with the race between an individual cheetah, say, and a gazelle, which is run in real time. The race in evolutionary time is a race to build up equipment for races run in real time. And what that actually means is that genes for making the equipment to outsmart or outrun the other side build up in the gene pools on the two sides. Second – and this is a point that Darwin himself knew well – the equipment for running fast is used to outrun rivals of the same species, who are fleeing from the same predator. The well- known joke, which has an almost Aesopian ring to it, about the running shoes and the bear is apposite. When a cheetah chases a herd of gazelles, it may be more important for an individual gazelle to outrun the slowest member of the herd than to outrun the cheetah.

Now that I have introduced the terminology of the arms race, you can see that trees in a forest, too, are engaged in one. Individual trees are racing towards the sun, against their immediate neighbours in the forest. This race is particularly keen when an old tree dies and leaves a vacant slot in the canopy. The echoing crash of an old tree falling is the starting gun for a race, in real time (although a slower real time than we animals are accustomed to), between saplings that have been waiting for just such a chance. And the winner is likely to be an individual tree that is well equipped, by genes that prospered through ancestral arms races in evolutionary time, to grow fast and high.

The arms race between species of forest trees is a symmetrical race. Both sides are trying to achieve the same thing: a place in the canopy. The arms race between predators and prey is an asymmetric arms race: an arms race between weapons of attack and weapons of defence. The same is true of the arms race between parasites and hosts. And there are even, though it may seem surprising, arms races between males and females within a species, and between parents and offspring.

One thing about arms races that might worry enthusiasts for intelligent design is the heavy dose of futility that loads them down. If we are going to postulate a designer of the cheetah, he has evidently put every ounce of his designing expertise into the task of perfecting a superlative killer. One look at that magnificent running machine leaves us in no doubt. The cheetah, if we are going to talk design at all, is superbly designed for killing gazelles. But the very same designer has equally evidently strained every nerve to design a gazelle that is superbly equipped to escape from those very same cheetahs. For heaven’s sake, whose side is the designer on? When you look at the cheetah’s taut muscles and flexing backbone, you must conclude that the designer wants the cheetah to win the race. But when you look at the sprinting, jinking, dodging gazelle, you reach exactly the opposite conclusion. Does the designer’s left hand not know what his right hand is doing? Is he a sadist, who enjoys the spectator sport and is forever upping the ante on both sides to increase the thrill of the chase? Did He who made the lamb make thee?

Is it really part of the divine plan that the leopard shall lie down with the kid, and the lion eat straw like the ox? In that case, what price the formidable carnassial teeth, the murderous claws of the lion and the leopard? Whence the breathtaking speed and agile escapology of the antelope and the zebra? Needless to say, no such problems arise on the evolutionary interpretation of what is going on. Each side is struggling to outwit the other because, on both sides, those individuals who succeed will automatically pass on the genes that contributed to their success. Ideas of ‘futility’ and ‘waste’ spring to our minds because we are human, and capable of looking at the welfare of the whole ecosystem. Natural selection cares only for the survival and reproduction of individual genes.

It’s like the trees in the forest. Just as each tree has an economy, in which goods that are put into trunks are not available for fruits or leaves, so cheetahs and gazelles each have their own internal economy. Running fast is costly, not just in energy ultimately wrung from the sun but in the materials that go into the making of muscles, bones and sinews – the machinery of speed and acceleration. The food that a gazelle ingests in the form of plant material is finite. Whatever is spent on muscles and long legs for running has to be taken away from some other department of life, such as making babies, on which the animal might ideally ‘prefer’ to spend its resources. There is an extremely complicated balance of compromises to be micro-managed. We can’t know all the details but we do know (it is an unbreakable law of economics) that it is possible to spend too much on one department of life, thereby taking resources away from some other department of life. An individual that puts more than the ideal amount into running may save its own skin. But in the Darwinian stakes it will be out- competed by a rival individual of the same species, who skimps a little on running speed and hence incurs a greater risk of being eaten, but who gets the balance right and ends up with more descendants to pass on the genes for getting the balance right.

It isn’t just energy and costly materials that have to be correctly balanced. There’s also risk: and risk, too, is no stranger to the calculations of economists. Legs that are long and thin are good at running fast. Inevitably, they are also good at breaking. All too regularly a racehorse will break a leg in the heat of a race, and usually is promptly executed. As we saw in Chapter 3, the reason they are so vulnerable is that they have been overbred to be fast, at the expense of everything else. Gazelles and cheetahs have also been selectively bred for speed – naturally, not artificially selected – and they too would be vulnerable to fractures if nature were to overbreed them for speed. But nature never overbreeds for anything. Nature gets the balance right. The world is full of genes for getting the balance right: that is why they are there! What it means in practice is that individuals with a genetic tendency to develop exceptionally long and spindly legs, which are admittedly superior for running, are less likely to pass on their genes, on average, than slightly slower individuals whose less spindly legs are less likely to break. This is just one hypothetical example of the many hundreds of trade-offs and compromises that all animals and plants juggle. They juggle with risks and they juggle with economic trade-offs. It is, of course, not the individual animals and plants that do the juggling and balancing. It is the relative numbers of alternative genes in gene pools that are juggled and balanced, by natural selection.

As you would expect, the optimum compromise in a trade-off is not fixed. In gazelles, the trade-off between running speed and other demands within the economy of the body will shift its optimum depending upon the prevalence of carnivores in the area. It’s the same story as for the guppies of Chapter 5. If there are few predators around, the gazelle’s optimum leg length will shorten: the most successful individuals will be the ones whose genes predispose them to shunt some energy and material away from legs and into, say, making babies, or laying down fat for the winter. These are also the individuals who are less likely to break their legs. Conversely, if the number of predators increases, the optimum balance will shift towards longer legs, greater danger of fractures, and less energy and material to spend on those aspects of the body’s economy that are not concerned with running fast.

And just the same kinds of implicit calculation will balance up the optimum compromises in the predators. A cheetah who breaks her leg will undoubtedly die of starvation, and so will her cubs. But, depending on how difficult it is to find a meal, the risk of failing to catch enough food if she runs too slowly may outweigh the risk of breaking a leg through being equipped with the wherewithal to run too fast.

Predators and prey are locked in an arms race in which each side is unwittingly pressing the other to shift its optimum – in the economic and risk compromises of life – further and further in the same direction: either literally in the same direction, for example towards increased running speed; or in the same direction in the looser sense of being aimed at the predator/prey arms race rather than some other department of life such as milk production. Given that both sides have to balance the risks of, say, running too fast (breaking legs or skimping on the other parts of the bodily economy) against the risks of running too slowly (failing to catch prey, or failing to escape, respectively), each side is pushing the other in the same direction, in a sort of grim folie à deux.

Well, perhaps folie (madness) doesn’t quite do justice to the seriousness of the matter, for the penalty of failure on either side is death – murder on the side of the prey, starvation on the side of the predator. But à deux captures handily the feeling that, if only hunter and hunted could sit down together and hammer out a sensible agreement, everybody would be better off. Just as with the trees in the Forest of Friendship, it is easy to see how such a compact would benefit them, if only it could be made to stick. The same sense of futility as we encountered in the forest pervades the predator/prey arms race. Over evolutionary time, predators get better at catching prey, which prompts prey animals to get better at evading capture. Both sides in parallel improve their equipment to survive, but neither necessarily survives any better – because the other side is improving its equipment too.

On the other hand, it is easy to see how a central planner, with the welfare of the whole community at heart, might umpire an agreement in the following terms, along the lines of the Forest of Friendship. Let both sides ‘agree’ to scale down their armoury: both sides shift resources to other departments of life, and all will do better as a result. Just the same, of course, can happen in a human arms race. We wouldn’t need our fighters if you didn’t have your bombers. You wouldn’t need your missiles if we didn’t have ours. We could both save billions if we halved our armaments spending and put the money into ploughshares. And now, having halved our arms budget and reached a stable stand-off, let’s halve it again. The trick is to do it in synchrony with each other, so that each side remains exactly as well equipped to counter the other’s steadily de-escalating arms budget. Such planned de-escalation has to be just that – planned. And, once again, planned is precisely what evolution is not. Just as with the trees in the forest, escalation is inevitable, right up until the moment when it no longer pays a typical individual to escalate any further. Evolution, unlike a designer, never stops to consider whether there might be a better way – a mutualistic way – for all concerned, rather than bilateral escalation for a selfish advantage: an advantage that is neutralized precisely because the escalation is mutual.

The temptation to think like a planner has long been rife among ‘pop ecologists’, and even academic ecologists sometimes come perilously close to it. The tempting notion of ‘prudent predators’, for example, was dreamed up not by some tree-hugging airhead but by a distinguished American ecologist.

The idea of prudent predators is this. Everybody knows that, from the point of view of humanity as a whole, we’d be better off if we all refrained from overfishing an important food species, such as the cod, to extinction. That is why governments and NGOs in stately conclave meet to draw up quotas and restrictions. That is why the precise mesh size of fishing nets is minutely specified by government decree, and that is why gunboats patrol the seas in pursuit of dissenting trawlermen. We humans, on our good days and when properly policed, are ‘prudent predators’. Therefore – or so it seems to certain ecologists – shouldn’t we expect wild predators, like wolves or lions, to be prudent predators too? The answer is no. No. No. No. And it is worthwhile understanding why, because it’s an interesting point, one that the forest trees and this whole chapter should have prepared us for.

A planner – an ecosystem designer with the welfare of the whole community of wild animals at heart – could indeed calculate an optimum culling policy, which lions, for example, should ideally adopt. Don’t take more than a certain quota from any one species of antelope. Spare pregnant females, and don’t take young adults full of reproductive potential. Avoid eating members of rare species, which might be in danger of extinction and might come in useful in future, if conditions change. If only all the lions in the country would abide by the agreed norms and quotas, carefully calculated to be ‘sustainable’, wouldn’t that be nice? And so sensible. If only!

Well, it would be sensible, and it is what a designer would prescribe, at least if he had the welfare of the ecosystem as a whole at heart. But it isn’t what natural selection would prescribe (mainly because natural selection, lacking foresight, cannot prescribe at all) and it isn’t what happens! Here’s why, and it is again the same story as for the trees in the forest. Imagine that, by some quirk of leonine diplomacy, a majority of lions in an area somehow managed to agree to limit their hunting to sustainable levels. But now, suppose that in this otherwise restrained and public-spirited population, a mutant gene arose that caused an individual lion to break away from the agreement and exploit the prey population to the uttermost, even at the risk of driving the prey species extinct. Would natural selection penalize the rebellious selfish gene? Alas, it would not. Offspring of the rebel lion, possessors of the rebel gene, would out-compete and out-reproduce their rivals in the lion population. Within a few generations, the rebel gene would spread through the population and nothing would be left of the original amicable compact. He who gets the lion’s share passes on the genes for doing so.

But, the planning enthusiast will protest, when all the lions are behaving selfishly and over-hunting the prey species to the point of extinction, everybody is worse off, even the individual lions that are the most successful hunters. Ultimately, if all the prey go extinct, the entire lion population will too. Surely, the planner insists, natural selection will step in to stop that happening? Once again alas, and once again no. The problem is that natural selection doesn’t ‘step in’, natural selection doesn’t look into the future, and natural selection doesn’t choose between rival groups. If it did, there would be some chance that prudent predation could be favoured. Natural selection, as Darwin realized much more clearly than many of his successors, chooses between rival individuals within a population. Even if the entire population is diving to extinction, driven down by individual competition, natural selection will still favour the most competitive individuals, right up to the moment when the last one dies. Natural selection can drive a population to extinction, while constantly favouring, to the bitter end, those competitive genes that are destined to be the last to go extinct. The hypothetical planner that I have imagined is a certain kind of economist, a welfare economist calculating an optimum strategy for a whole population, or an entire ecosystem. If we must make economic analogies, we should think instead of Adam Smith’s ‘invisible hand’.

EVOLUTIONARY THEODICY?

But now I want to leave economics altogether. We shall stay with the idea of a planner, a designer, but our planner will be a moral philosopher rather than an economist. A beneficent designer might – you’d idealistically think – seek to minimize suffering. This is not incompatible with economic welfare, but the system created will differ in detail. And, once again, it unfortunately doesn’t happen in nature. Why should it? Terrible but true, the suffering among wild animals is so appalling that sensitive souls would best not contemplate it. Darwin knew whereof he spoke when he said, in a letter to his friend Hooker, ‘What a book a devil’s chaplain might write on the clumsy, wasteful, blundering low and horridly cruel works of nature.’ The memorable phrase ‘devil’s chaplain’ gave me my title for one of my previous books, and in another I put it like this:

[N]ature is neither kind nor unkind. She is neither against suffering, nor for it. Nature is not interested in suffering one way or the other unless it affects the survival of DNA. It is easy to imagine a gene that, say, tranquillises gazelles when they are about to suffer a killing bite. Would such a gene be favoured by natural selection? Not unless the act of tranquillising a gazelle improved that gene’s chances of being propagated into future generations. It is hard to see why this should be so and we may therefore guess that gazelles suffer horrible pain and fear when they are pursued to the death – as most of them eventually are. The total amount of suffering per year in the natural world is beyond all decent contemplation. During the minute that it takes me to compose this sentence, thousands of animals are being eaten alive, others are running for their lives, whimpering with fear, others are being slowly devoured from within by rasping parasites, thousands of all kinds are dying of starvation, thirst and disease. It must be so. If there is ever a time of plenty, this very fact will automatically lead to an increase in population until the natural state of starvation and misery is restored.

Parasites probably cause even more suffering than predators, and understanding their evolutionary rationale adds to, rather than mitigates, the sense of futility we experience when we contemplate it. I fulminate against it every time I get a cold (I have one now, as it happens). Maybe it is only a minor inconvenience, but it is so pointless! At least if you are eaten by an anaconda you can feel that you have contributed to the well-being of one of the lords of life. When you are eaten by a tiger, perhaps your last thought could be, What immortal hand or eye could frame thy fearful symmetry? (In what distant deeps or skies, burnt the fire of thine eyes?) But a virus! A virus has pointless futility written into its very DNA – actually, RNA in the case of the common cold virus, but the principle is the same. A virus exists for the sole purpose of making more viruses. Well, the same is ultimately true of tigers and snakes, but there it doesn’t seem so futile. The tiger and the snake may be DNA-replicating machines but they are beautiful, elegant, complicated, expensive DNA-replicating machines. I’ve given money to preserve the tiger, but who would think of giving money to preserve the common cold? It’s the futility of it that gets to me, as I blow my nose yet again and gasp for breath.

Futility? What nonsense. Sentimental, human nonsense. Natural selection is all futile. It is all about the survival of self-replicating instructions for self-replication. If a variant of DNA survives through an anaconda swallowing me whole, or a variant of RNA survives by making me sneeze, then that is all we need by way of explanation. Viruses and tigers are both built by coded instructions whose ultimate message is, like a computer virus, ‘Duplicate me.’ In the case of the cold virus, the instruction is executed rather directly. A tiger’s DNA is also a ‘duplicate me’ program, but it contains an almost fantastically large digression as an essential part of the efficient execution of its fundamental message. That digression is a tiger, complete with fangs, claws, running muscles, stalking and pouncing instincts. The tiger’s DNA says, ‘Duplicate me by the roundabout route of building a tiger first.’ At the same time, antelope DNA says, ‘Duplicate me by the roundabout route of building an antelope first, complete with long legs and fast muscles, complete with timorous instincts and finely honed sense organs tuned to the danger from tigers.’ Suffering is a byproduct of evolution by natural selection, an inevitable consequence that may worry us in our more sympathetic moments but cannot be expected to worry a tiger – even if a tiger can be said to worry about anything at all – and certainly cannot be expected to worry its genes.

Theologians worry about the problems of suffering and evil, to the extent that they have even invented a name, ‘theodicy’ (literally, ‘justice of God’), for the enterprise of trying to reconcile it with the presumed beneficence of God. Evolutionary biologists see no problem, because evil and suffering don’t count for anything, one way or the other, in the calculus of gene survival. Nevertheless, we do need to consider the problem of pain. Where, on the evolutionary view, does it come from?

Pain, like everything else about life, we presume, is a Darwinian device, which functions to improve the sufferer’s survival. Brains are built with a rule of thumb such as, ‘If you experience the sensation of pain, stop whatever you are doing and don’t do it again.’ It remains a matter for interesting discussion why it has to be so damned painful. Theoretically, you’d think, the equivalent of a little red flag could painlessly be raised somewhere in the brain, whenever the animal does something that damages it: picks up a red-hot cinder, perhaps. An imperative admonition, ‘Don’t do that again!’ or a painless change in the wiring diagram of the brain such that, as a matter of fact, the animal doesn’t do it again, would seem, on the face of it, enough. Why the searing agony, an agony that can last for days, and from which the memory may never shake itself free? Perhaps grappling with this question is evolutionary theory’s own version of theodicy. Why so painful? What’s wrong with the little red flag?

I don’t have a decisive answer. One intriguing possibility is this. What if the brain is subject to opposing desires and impulses, and there is some kind of internal tussle between them? Subjectively, we know the feeling well. We may be in a conflict between, say, hunger and a desire to be slim. Or we may be in a conflict between anger and fear. Or between sexual desire and a shy fear of rejection, or a conscience that urges fidelity. We can literally feel the tug of war within us, as our conflicting desires battle it out. Now, back to pain and its possible superiority over a ‘red flag’. Just as the desire to be slim can over-rule hunger, it is clearly possible to over-rule the desire to escape pain. Torture victims may succumb eventually, but they often go through a phase of enduring considerable pain rather than, say, betray their comrades or their country or their ideology. In so far as natural selection can be said to ‘want’ anything, natural selection doesn’t want individuals to sacrifice themselves for the love of a country, or for the sake of an ideology or a party or a group or a species. Natural selection is ‘against’ individuals over-ruling the warning sensations of pain. Natural selection ‘wants’ us to survive, or more specifically, to reproduce, and be blowed to country, ideology or their non-human equivalents. As far as natural selection is concerned, little red flags will be favoured only if they are never over-ruled.

Now, despite philosophical difficulties, I think that instances where pain was over-ruled for non-Darwinian reasons – reasons of loyalty to country, ideology, etc. – would be more frequent if we had a ‘red flag’ in the brain rather than real, full-on, intolerable pain. Suppose genetic mutants arose who could not feel the excruciating agony of pain but relied upon a ‘red flag’ system to keep them away from bodily damage. It would be so easy for them to resist torture, they’d promptly be recruited as spies. Except that it would be so easy to recruit agents prepared to bear torture that torture would simply stop being used as a method of extortion. But, in a wild state, would such pain-free, red-flag mutants survive better than rival individuals whose brains do pain in earnest? Would they survive to pass on the genes for red-flag pain substitutes? Even setting aside the special circumstance of torture, and the special circumstances of loyalty to ideologies, I think we can see that the answer might be no. And we can imagine non-human equivalents.

As a matter of interest, there are aberrant individuals who cannot feel pain, and they usually come to a bad end. ‘Congenital insensitivity to pain with anhidrosis’ (CIPA) is a rare genetic abnormality in which the patient lacks pain receptor cells in the skin (and also – that’s the ‘anhidrosis’ – doesn’t sweat). Admittedly, CIPA patients don’t have a built-in ‘red flag’ system to compensate for the breakdown of the pain system, but you’d think they could be taught to be cognitively aware of the need to avoid bodily damage – a learned red flag system. At all events, CIPA patients succumb to a variety of unpleasant consequences of their inability to feel pain, including burns, breakages, multiple scars, infections, untreated appendicitis and scratches to the eyeballs. More unexpectedly, they also suffer serious damage to their joints because, unlike the rest of us, they don’t shift their posture when they have been sitting or lying in one position for a long time. Some patients set timers to remind themselves to change position frequently during the day.

Even if a ‘red flag’ system in the brain could be made effective, there seems to be no reason why natural selection would positively favour it over a real pain system just because it is less unpleasant. Unlike our hypothetically beneficent designer, natural selection is indifferent to the intensity of suffering – except in so far as it affects survival and reproduction. And, just as we should expect if the survival of the fittest, rather than design, underlies the world of nature, the world of nature seems to take no steps at all to reduce the sum total of suffering. Stephen Jay Gould reflected on such matters in a nice essay on ‘Nonmoral nature’. I learned from it that Darwin’s famous revulsion at the Ichneumonidae, which I quoted at the end of the previous chapter, was far from unique among Victorian thinkers.

Ichneumon wasps, with their habit of paralysing but not killing their victim, before laying an egg in it with the promise of a larva gnawing it hollow from within, and the cruelty of nature generally, were major preoccupations of Victorian theodicy. It’s easy to see why. The female wasps lay their eggs in live insect prey, such as caterpillars, but not before carefully seeking out with their sting each nerve ganglion in turn, in such a way that the prey is paralysed, but still stays alive. It must be kept alive to provide fresh meat for the growing wasp larva feeding inside. And the larva, for its part, takes care to eat the internal organs in a judicious order. It begins by taking out the fat bodies and digestive organs, leaving the vital heart and nervous system till last – they are necessary, you see, to keep the caterpillar alive. As Darwin so poignantly wondered, what kind of beneficent designer would have dreamed that up? I don’t know whether caterpillars can feel pain. I devoutly hope not. But what I do know is that natural selection would in any case take no steps to dull their pain, if the job could be accomplished more economically by simply paralysing their movements.