CLIMBING MOUNT IMPROBABLE
Chapter 1: Facing Mount Rushmore
I have just listened to a lecture in which the topic for discussion was the fig. Not a botanical lecture, a literary one. We got the fig in literature, the fig as metaphor, changing perceptions of the fig, the fig as emblem of pudenda and the fig leaf as modest concealer of them, „fig‟ as an insult, the social construction of the fig, D.H.Lawrence on how to eat a fig in society, „reading fig‟ and, I rather think, „the fig as text.‟. The speaker‟s final pensée was the
following. He recalled to us the Genesis story of Eve‟s tempting Adam to eat of the fruit of the tree of knowledge. Genesis doesn‟t specify, he reminded us,
which fruit it was. Traditionally, people take it to be an apple. The lecturer suspected that actually it was a fig, and with this piquant little shaft he ended his talk.
This kind of thing is the stock-in-trade of a certain kind of literary mind, but it provokes me to literal-mindedness. The speaker obviously knows that there never was a Garden of Eden, never a tree of knowledge of good and evil. So what is he actually trying to say? I suppose he had a vague feeling that „somehow‟, „if you will‟, „at some level‟, „in some sense‟, „if I may put it this way‟ it is somehow „right‟ that the fruit in the story „should‟ have been a fig. But
enough of this foolery. It is not that we should be literalist and Gradgrindian, but our elegant lecturer was missing so much. There is genuine paradox and
real poetry lurking in the fig, with subtleties to exercise an inquiring mind and wonders to uplift an aesthetic one. In this book I want to move to a position where I can tell the true story of the fig. But the fig story is only one out of millions that all have the same Darwinian grammar and logic – albeit the fig
story is among the most satisfyingly intricate in all evolution. To anticipate the central metaphor of the book, the fig tree stands atop one of the highest peaks on the massif of Mount Improbable. But peaks as high the fig‟s are best
conquered at the end of the expedition. Before that there is much that needs to be said, a whole vision of life that needs to be developed and explained, puzzles that need to be solved and paradoxes that must be disarmed.
As I said, the story of the fig is, at the deepest level, the same story as for
every other living creature on this planet. Though they differ in surface detail, all are variations on the theme of DNA and the thirty million ways by which it propagates itself. On our route we shall have occasion to look at spider webs – at the bewildering, though unconscious, ingenuity with which they are made and how they work. We shall reconstruct the slow, gradual evolution of wings and of elephant trunks. We shall see that „the‟ eye, legendarily difficult
though its evolution sometimes seems, has actually evolved at least 40 and probably 60 times independently all around the animal kingdom. We shall program computers to assist our imagination in moving easily through a gigantic museum of all the countless creatures that have ever lived and died, and their even more numerous, imaginary cousins who have never been born. We shall wander the paths of Mount Improbable, admiring its vertical precipices from afar, but always restlessly seeking the gently graded slopes on the other side. The meaning of the parable of Mount Improbable will be made clear, and much else besides. I need to begin by clarifying the problem of apparent design in nature, its relationship to true, human design and its relationship to chance. This is the purpose of Chapter 1.
The Natural History Museum in London has a quirky collection of stones that chance to resemble familiar objects: a boot, a hand, a baby‟s skull, a duck, a
fish. They were sent in by people who genuinely suspected that the resemblance might mean something. But ordinary stones weather into such a welter of shapes, it is not surprising if occasionally we find one that calls to mind a boot, or a duck. Out of all the stones that people notice as they walk about, the museum has preserved the ones that they pick up and keep as curiosities. Thousands of stones remain uncollected because they are just stones. The coincidences of resemblance in this museum collection are meaningless, though amusing. The same is true when we think we see faces, or animal shapes, in clouds or cliff profiles. The resemblances are accidents.
Fig 1.1 A pure accident. President Kennedy’s face in a hillside.
This craggy hillside is supposed to suggest the profile of the late President Kennedy. Once you have been told, you can just see a slight resemblance to either John or Robert Kennedy. But some don‟t see it at all, and it is certainly
easy to believe that the resemblance is accidental. You couldn‟t, on the other hand, persuade a reasonable person that Mount Rushmore, in South Dakota, had just happened to weather into the features of Presidents Washington, Jefferson, Lincoln and Theodore Roosevelt. We do not need to be told that these were deliberately carved (under the direction of Gutzon Borglum). They are obviously not accidental: they have design written all over them.
The difference between Mount Rushmore and the weathered likeness of John Kennedy (or Mont St Pierre in Mauritius or all such curiosities of natural weathering) is this. The sheer number of details in which the Mount Rushmore faces resemble the real thing is too great to have come about by chance. The faces are clearly recognizable, moreover, when seen from all different angles. Figure 1.1‟s chance resemblance to President Kennedy, on the other
hand, is only noticed if the cliff is seen from a particular angle and in a particular light. Yes, a rock can weather into the shape of a nose seen from a certain vantage point, and maybe a couple of other rocks happen to have tumbled into the shape of lips. It is not much to ask of chance that it should produce a modest coincidence like this, especially if viewers have all possible angles to choose from and only one gives the resemblance (and there is the added fact, which I‟ll return to in a moment, that the human brain seems actively eager to see faces: it seeks them out). But Mount Rushmore is another matter. Its four heads are clearly designed. A sculptor conceived
them, drew them out on paper, made meticulous measurements all over the cliff, and supervised teams of workmen who wielded pneumatic drills and dynamite to carve out the four faces, each 60 feet high. The weather could
have done the same job as the artfully deployed dynamite. But of all the possible ways of weathering a mountain, only a tiny minority would be speaking likenesses of four particular human beings. Even if we didn‟t know
the history of Mount Rushmore, we‟d estimate the odds against its four heads being carved by accidental weathering as astronomically high – like tossing a
coin 40 times and getting heads every time.
I think that the distinction between accident and design is clear, in principle if not always in practice, but this chapter will introduce a third category of objects which is harder to distinguish. I shall call them designoid, pronounced „design-
oid‟ not „dezziggnoid.‟ Designoid objects are living bodies and their
products. Designoid objects look designed, so much so that some people –
probably, alas, most people – think that they are designed. These people
are wrong. But they are right in their conviction that designoid objects cannot be the result of chance. Designoid objects are not accidental. They have in fact been shaped by a magnificently nonrandom process which creates an almost perfect illusion of design.
Figure 1.2 An undesigned, but not accidental, resemblance. An ant (a) and an ant-mimicking beetle (b).
Here is a living sculpture. Beetles in general don‟t look like ants. So, if I see a
beetle that looks almost exactly like an ant – a beetle, moreover, that makes
its living entirely in an ant‟s nest – I shall rightly suspect that the coincidence
means something. The top animal is actually a beetle – its closer cousins are
common or garden beetles – but it looks like an ant, walks like an ant, and lives among ants in an ants‟ nest. The one at the bottom is a real ant. As with
any realistic statue, the resemblance to the model is not an accident. It demands an explanation other than sheer chance. What kind of an explanation? Since all beetles that look strikingly like ants live in ants‟ nests, or at least in close association with ants, could it be some chemical substance from the ants, or some infection from the ants, rubbing off on the beetles and changing the way they grow? Definitely not. We shall come to the true explanation – Darwinian natural selection – later. For the moment, it is
enough that we are sure this resemblance, and other examples of „mimicry,‟ are not accidental. They are either designed or they are due to some process that produces results just as impressive as design. We shall look at some other examples of animal mimicry, leaving open, for the moment, the explanation of how these remarkable resemblances come about.
Figure 1.3 a. A real termite. b. a beetle mimicking a termite. c. How the trick is done
The previous example shows what a good job beetle flesh can do if it „sets out to mimic‟ a different kind of insect. But now look at the creature in Figure
1.3b. It appears to be a termite. Figure 1.3a is a real termite, for comparison. The specimen in Figure 1.3b is an insect, but it is not a termite. It
is, in fact, a beetle. I admit that I‟ve seen better mimics in the insect world, including the ant-mimicking beetle of the previous example. The „beetle‟ here
is just a little odd. Its legs seem to lack proper joints, like little twisty balloons. Since, like any other insect, a beetle has jointed legs at its disposal, you might hope for a better shot at mimicking a termite‟s jointed legs. So, what
is the solution to this conundrum? Why does this statue look like an inflated dummy rather than like a real, jointed insect. The answer can be seen in Figure 1.3c, which is one of the most astonishing spectacles in all natural history. It shows the termite-mimicking beetle in side view. The true head of the beetle is a diminutive affair (you can see the eye just near the normal, jointed antennae), attached to a slender trunk or thorax bearing three normal, jointed beetle legs, on which it actually walks. It is with the abdomen that the trick is done. It is arched backwards so that it hangs over and completely covers the head, thorax and legs like a parasol. The entire „termite‟ is
constructed from the (anatomically) rear half of the beetle‟s abdomen. The
„termite head‟ is the rear tip of the beetle‟s abdomen. The „termite legs‟ and
„antennae‟ are flapping excrescences of the abdomen. No wonder the quality
of the mimicry is not quite up to the standard of the beetle‟s ant-mimicking
cousin of the previous picture. This termite-mimicking beetle, by the way, lives in termite nests, making its living as a parasite in much the same way as Figure 1.2‟s ant-mimicking beetle makes its living among ants. Although the quality of the resemblance is less, when you consider its starting materials the termite-mimicking beetle seems to achieve a more impressive feat of sculpture than the ant-mimicking beetle. This is because the ant-mimic does it by modifying each bit of its body to look like the corresponding bit of the ant‟s body. But the
termite-mimic does it by modifying a completely different bit of itself – the
abdomen – to look like all the bits of the termite.
Figure 1.4 Perfection of camouflage. Leafy Sea Dragon.
My own favourite among animal „statues‟ is the leafy sea dragon. It is a fish, a
kind of sea-horse, whose body is sculpted into the shape of seaweed. This gives it protection, for it lives among seaweed and is remarkably difficult to see there. Its mimicry is too uncannily good to be accidental in any simple sense. It lies closer to Mount Rushmore than to the Kennedy cliff. My confidence is based partly upon the sheer number of ways in which it
impresses us by looking like something that it isn‟t; and partly upon the fact that fish don‟t normally have projections of anything like that shape. In this respect
the leafy sea dragon‟s feat compares with the termite mimic, rather than the ant mimic.
So far we have talked of objects that impress us as realistic sculptures do, objects that we feel can‟t be accidental because they look too strikingly like other objects. Leafy sea dragons and ant-mimicking beetles are designoid statues: they overwhelmingly look as if they have been designed by an artist to resemble something else. But statues are only one kind of object that humans design. Other human artefacts impress us not by resembling something but by being unmistakably useful for some purpose. An aeroplane is useful for flying. A pot is useful for holding water. A knife is useful for cutting things.
If you offered a reward for stones that were naturally sharp enough to cut things, and also for stones that happened to be of a shape to hold water, you‟d probably be sent some effective makeshifts. Flints often fracture in such a way as to leave a good keen edge, and if you wandered the quarries and screes of the world you‟d certainly find some handy natural blades. Among the richness
of shapes into which stones can weather, some would happen to include concavities that hold water. Certain types of crystal naturally encrust around a hollow, albeit chunky, sphere which, when it splits in half, yields two serviceable cups. These stones even have a name: geode. I use a geode as a paperweight on my desk, and I‟d use it to drink from if its interior were not roughly pitted and therefore hard to wash.
It is easy to devise measures of efficiency that would show up natural pots as less efficient than manmade ones. Efficiency is some measure of benefit divided by cost. The benefit of a pot could be measured as the quantity of water that it holds. Cost can conveniently be measured in equivalent units: the quantity of the material of the pot itself. Efficiency might be defined as the volume of water that a pot can hold divided by the volume of material that goes to make the pot itself. The hollow stone on my desk holds 87.5 cc of water. The volume of the stone itself (which I measured by Archimedes‟s famous Eureka-in-the-Bath method) is 130 cc. The efficiency of this „pot‟ is
therefore about two thirds. This is a very low efficiency, not surprisingly so
since the stone was never designed to hold water. It just happens to hold water. I have just done the same measurements on a wineglass, whose efficiency turns out to be about 3.5. My silver cream jug is even more efficient. It holds 250 cc of water while the silver of which it is made displaces a mere 20 cc. Its efficiency is therefore as high as 12.5.
Not all human-designed pots are efficient in this sense. A chunky pot from the kitchen cupboard holds 190 cc of water while using up a massive 400 cc of marble. Its „efficiency‟ is therefore only 0.475, even lower than the totally undesigned hollow stone. How can this be? The answer is revealing. This marble pot is in fact a mortar. It is not designed just to hold liquid. It is a hand mill for grinding spices and other foods with a pestle: a stout rod which is wielded with great force against the inside of the mortar. You couldn‟t use a
wineglass as a mortar: it would shatter under the force. The measure of efficiency that we devised for pots is not suitable when the pot is designed as a mortar. We should devise some other benefit/cost ratio, where benefit takes account of strength against being broken by a pestle. Would the natural geode, then, qualify as a well-designed mortar? It would probably pass the strength test but if you tried to use it as a mortar its rough and craggy interior would soon prove a disadvantage, the crevices protecting grains from the pestle. You‟d have to improve your measure of the efficiency of a mortar by including some index of smoothness of internal curvature. That my marble mortar is designed can be discerned from other evidence: its perfectly circular plan section, coupled with its elegantly turned lip and plinth seen in elevation.
We could devise similar measures of the efficiency of knives, and I have no doubt that the naturally flaked flints that we happen to pick up in a quarry would compare unfavourably, not only with Sheffield steel blades but with the elegantly sculpted flints that museums display in Late Stone Age collections.
There is another sense in which natural, accidental, pots and knives are inefficient compared with their designed equivalents. In the course of finding one usefully sharp flint tool, or one usefully watertight stone vessel, a huge number of useless stones had to be examined and discarded. When we measure the water held by a pot, and divide by the volume of stone or clay in
the material of the pot, it might be fairer to add into the denominator the cost of the stone or clay discarded. In the case of a manmade pot thrown on a wheel, this additional cost would be negligible. In the case of a carved sculpture the cost of discarded chippings would be present but small. In the case of the accidental, objet trouvé pot or knife, the „discard cost‟ would be colossal. Most
stones don‟t hold water and are not sharp. An industry that was entirely based
upon objets trouvés, upon found objects as tools and utensils, rather than
artificially shaped tools and utensils, would have a huge dead weight of inefficiency in the spoil heaps of alternatives discarded as useless. Design is efficient compared with finding.
Figure 1.5 A designoid pot. Pitcher plant.
Let‟s turn our attention now to designoid objects – living things that look as
though they have been designed but have actually been put together by a completely different process – beginning with designoid pots. The pitcher
plant could be seen as just another kind of pot, but it has an elegant „economy ratio,‟ comparable to the wine glass that I measured, if not the silver jug. It
gives every appearance of being excellently well designed, not just to hold water but to drown insects and digest them. It concocts a subtle perfume which insects find irresistible. The smell, abetted by a seductive colour pattern, lures prey to the top of the pitcher. There the insects find themselves on a steep slide whose treacherous slipperiness is more than accidental, set about with downward-facing hairs well-placed to impede their last struggle. When they fall, as they nearly always do, into the dark belly of the pitcher, they find more than just water in which to drown. The details, brought to my attention by my colleague Dr Barrie Juniper, are remarkable and I‟ll briefly tell the story.
It is one thing to trap insects but the pitcher plant lacks jaws, muscles and teeth with which to reduce them to a state fit for digesting. Perhaps plants could grow teeth and munching jaws but in practice there is an easier solution. The water in the pitcher is home to a rich community of maggots and other creatures. They live nowhere else but in the enclosed ponds created by pitcher plants, and they are endowed with the jaws that the plant itself lacks. The corpses of the pitcher plant‟s drowned victims are devoured and
decomposed by the mouthparts and digestive juices of its maggot
accomplices. The plant itself subsists on the detritus and excretory products, which it absorbs through the lining of the pitcher.
The pitcher plant doesn‟t just passively accept the services of maggots that happen to fall into its private pool. The plant works actively to provide the maggots with a service that they need in their turn. Analyse the water in a pitcher plant and you find a singular fact. It is not fœtid as might be expected
of standing water in such conditions, but strangely rich in oxygen. Without this oxygen the vital maggots could not flourish, but where does it come from? It is manufactured by the pitcher plant itself, and the plant gives every apparent indication of being specifically designed to oxygenate the water. The cells that line the pitcher are richer in oxygen-producing chlorophyll than the outside cells that face the sun and air. This surprising reversal of apparent common sense is explicable: the inside cells are specialised to secrete oxygen directly into the water inside the pitcher. The pitcher plant does not just borrow its vicarious jaws: it hires them, paying in the currency of oxygen.
Other designoid traps are common. The Venus‟s fly trap is as elegant as the
pitcher plant, with the added refinement of moving parts. The insect prey releases the trap by triggering sensitive hairs on the plant, whose jaws smartly close. The spider web is the most familiar of all animal traps, and we shall do it justice in the next chapter. An underwater equivalent is the net constructed by stream-dwelling caddis fly larvae. Caddis larvae are also notable for their feats as builders of houses for themselves. Different species use stones, sticks, leaves or tiny snail shells. A familiar sight in various parts of the world is the conical trap of the ant lion. This fearsome creature is the larva of – what
could sound more gentle? – a lacewing fly. The ant-lion lurks just under the
sand at the bottom of its pit, waiting for ants or other insects to fall in. The pit achieves its almost perfectly conical shape – which makes it hard for victims
to claw their way out – not by design but as a consequence of some simple
rules of physics, exploited by the way the ant-lion digs. From the bottom of the descending pit, it flicks sand right over the edge with a jerk of the head. Flicking sand from the bottom of a pit has the same effect as draining an hourglass from below: the sand forms itself naturally into a perfect cone of
Figure 1.6 Designoid pots made by animal artisans. (a) Potter wasp and (b) mason bee pots
Figure 1.6 brings us back to pots. Many solitary wasps lay their eggs on prey, stung to paralysis and hidden in a hole. They seal the hole up so that it is invisible, the larva feeds on the prey inside and finally emerges as a winged adult to complete the cycle. Most species of solitary wasp dig their nesting hole in the ground. The potter wasp makes its own „hole‟ out of clay – a round
pot, up a tree, mounted inconspicuously on a twig. Like the pitcher plant, this pot would score favourably on our efficiency test for apparent design. Solitary bees show a similar pattern of nesting in holes, but they feed their larvae on pollen instead of animal prey. Like the potter among wasps, many species of mason bee build their own pot nest. The pot in Figure 1.6 is made not from clay but from small stones cemented together. Apart from its resemblance to an efficient, man-made receptacle, there is something else rather wonderful about the particular specimen photographed. You see only one pot here, but there are actually four. The other three have been covered by the bee with hardened mud, to give an exquisite match to the surrounding rock. No predator would ever find the young larvae growing up in the pots. The only reason this cluster was seen, by my colleague Christopher O‟Toole on a visit to Israel, is that the bee had not quite finished covering the last pot.
These insect pots have all the hallmarks of „design.‟ In this case, unlike the
pitcher plant, they really were fashioned by the actions of a skilled – albeit
probably unconsciously so – creature. The pots of the potter wasp and
mason bee seem, on the face of it, closer to human-made pots than to the pitcher plant. But the wasp and the bee didn‟t consciously or deliberately design their pots. Although they were shaped, out of clay or stones, by behavioural actions of the insects, this is not importantly different from the way the insects‟ own bodies were made during embryonic development. This may
sound odd but let me explain. The nervous system grows in such a way that the muscles and limbs and jaws of the living wasp move in certain coordinated patterns. The consequence of these particular clockwork limb movements is