The Lagoon

by Armand Marie Leroi

  EKHINOS GENOS MIKRON – LONG-SPINED SEA URCHIN – CIDARIS CIDARI

  In his Greek Fishes D’Arcy Thompson identified the nameless sea urchin of the deep as Cidaris cidaris; he was certainly correct, for that is what I held in my hand. Aristotle says that this sea urchin is used as a remedy for stranguary, the urgent need to urinate coupled to the painful inability to do so, but I don’t think it’s used like that any more. In any case, he’s not very interested in its medicinal qualities, but is keen to explain its really long spines.

  Aristotle knows that spines protect sea urchins, so you would expect him to argue that the sea urchin of the deep needs particularly long spines for some functional reason, perhaps because the fishes down there are especially fierce. But that’s not the explanation he gives. Instead, he argues that they’re of no particular benefit to the sea urchin at all, but are simply the result of its ‘material nature’.

  Though he may heap scorn upon the crass materialism of his predecessors, Aristotle believes in the power of matter. A form, after all, cannot actually exist without it. To be sure, considering form and matter in the abstract, form is the more important: a form (a sphere) that manifests in different kinds of matter (wood, iron) remains essentially a sphere. Yet a sphere is a very abstract example; living forms are much more dependent on the stuff from which they’re made. You can make a wooden statue in the form of a man, but it obviously won’t walk or talk.

  Every Aristotelian animal is a triple-levelled hierarchy. At the bottom it’s made of elements, at the top organs. In the middle are the ‘uniform parts’ – blood, semen, milk, fat, marrow, flesh, sinew, hair, cartilage, bone. I would call them ‘tissues’ except that the term slightly distorts Aristotle’s meaning. We know that tissues are composed of cells, but Aristotle thinks that his uniform parts really are uniform – that is, totally devoid of microscopic structure. Every uniform part has its own particular ‘material nature’, a set of functional properties – soft, dry, moist, pliant, brittle – that depends on the particular mix of elements of which it is composed. And, although the uniform parts have functions in their own right (bone protects flesh), their real purpose is to be the stuff from which organs are made.

  Aristotle notices that the uniform parts differ among animals. Animals vary in the heat of their blood, the hardness of their bones, flesh, fat and skin, and the quantity of their marrow. Many animals, of course, have no blood, flesh or bone at all but have some other, analogous, usually unnamed, uniform parts instead. Aristotle seems to think that the uniform parts of any given animal kind have some innate norm, but that their quality and composition vary with health, diet and season. They are the basic units of his physiology and so the link between an animal’s environment and its body.

  That opens up a whole different kind of explanation for animal variety. Aristotle does not think that all variation is teleologically explicable. Some of it is directly due to the effects of the environment. The deeps in which the nameless sea urchin lives are, he says, cold. For that reason it does not have the warmth that it needs to ‘concoct’ or digest its food properly. (Sea urchins are, in his physiological scheme, rather cold creatures anyway.) For want of warmth, then, the sea urchin has a lot of ‘residual matter’ left over from concoction that it diverts into spines, which is why they are so long. The cold causes the spiny material to petrify, which is why they are so hard.

  This is all very mechanical. Long spines are just the result of ‘necessity’ – though here he means material rather than conditional necessity, for their length is not to be explained by any functional goal however remote but only by brute physiology. As it happens, sea urchins do grow different spines in response to the environment, a phenomenon that biologists call ‘phenotypic plasticity’, though that isn’t the explanation for Cidaris cidaris’ long spines for they are a feature of the species. For whatever reason, however, that is not how Aristotle sees it. He sees it as a case where matter has got the upper hand.

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  WHEN ARISTOTLE ANALYSES animal design he thinks like an architect or an engineer. His first thought is the purpose that a given organ serves. However, he’s also deeply aware of the stuff of which it’s made. These two kinds of explanation – conditional and material necessity – interact in subtle ways.

  Aristotle supposes that an animal’s organs are generally made of the right stuff, that the material natures of their uniform parts – the biophysics of their tissues – match the animal’s functional needs, yet he also allows that animals don’t always have the right stuff. The fact that the bodies of particular animals are made of certain kinds of matter limits the kinds of organs they have; it can even prevent them from having otherwise desirable organs. Conversely, animals produce material surplus to requirements – ‘residues’. Sometimes these residues are put to good use to make organs that aren’t, perhaps, vital but are desirable nevertheless. For Aristotle, as for an architect, function isn’t omnipotent; function stands in chains.

  His examples of how the properties of uniform parts match functional demands are a biophysicist’s delight. Snakes need to see what’s coming up behind them, but they can’t easily turn their bodies around because they don’t have feet, so instead they twist just their heads – which is why their vertebral columns are so flexible. When rays swim they undulate, so they, too, need a flexible skeleton – which is why they have cartilage rather than bones. The human oesophagus must be able to dilate to swallow food and yet resist being scraped as the food goes down – which is why it is both elastic and fleshy. The human penis must both droop and jaunt erect – which is why it’s made of some stuff that can be both soft and hard. These are all examples of conditional necessity where the consequent is a property of a uniform part.

  The epiglottis is a different story. Aristotle notices that the design of the neck is rather poor. Since the larynx and windpipe are located right in front of the oesophagus, animals easily choke on their own food. In mammals, nature has solved this problem by devising a lid for the larynx, the epiglottis, which closes during swallowing. But birds and reptiles don’t have an epiglottis. Why not? His answer is that their flesh and skin are ‘dry’ and so they can’t have one, since an epiglottis needs to be ‘fleshy’ to work. Nature has, therefore, devised some other device for them, contraction of the larynx.*

  Aristotle is usually confident that he knows what a given organ does. The spleen is mysterious. He’s reasonably sure that it’s not a vital organ. He knows that many blooded animals have only a very small spleen and thinks that some don’t have one at all, so he moots the possibility that it’s there to counterbalance the liver (he likes his organs to come in bilaterally symmetrical pairs); it may even aid it in ‘concocting’ nutrition (i.e. digestion); and that it helps to anchor the blood vessels. But mostly he thinks that it’s just a ‘residue’ – an excretion product that nature has put to various, not particularly essential, secondary uses.*

  Of course, some bodily productions really are just useless ‘residues’. Urine and faeces are obviously just excretory products, but Aristotle thought that bile is too. He was going against the grain of received opinion. The Greeks had forever probed the livers and gall bladders of sacrificed animals to predict the future. The more rationally minded physiologoi speculated that the gall bladder has a sensory function. The Hippocratics and Plato thought that bile was the product of disease. Aristotle rejects these ideas and, drawing once more on comparative data (some animals have gall bladders, others don’t), argues that bile is a residual product of blood that is produced in the liver, is excreted into the intestine and is quite useless: ‘Sometimes nature puts even the residues to some use, though that is no reason to seek a purpose for all of them. Actually, just because some have a purpose, many others are there necessarily.’*

  Sea urchins, snakes and sharks; gall bladders, penises and spleens – as Aristotle dissects and analyses, he’s picking his way along a precarious path. Above him soar the heights of Plato’s heedless teleology,
beneath him lies the abyss of the physiologoi’s relentless materialism. Aristotle, recognizing that neither cause can be ignored, considers every part in turn and assigns primacy now to functional goals, now to physiology, and often – and this is his great contribution – to the subtle interplay between the two. Yet, as we read The Parts of Animals, it becomes evident that beneath such explanations, which derive directly from his four causes, there is also a quite different set of principles at work – axioms that are neither directly teleological, nor material, but economic.

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  ZEUS, POSEIDON AND Athena are having a contest to see who can make the best thing. Zeus makes a man, Athena makes a house, Poseidon makes a bull. They ask a colleague, Momus, to judge their creations, and Momus promptly derides them all. The man, he says, should have a window into his heart so that we can see his plans; the house should be a caravan so that it can shift location; the bull should have (extra?) eyes under its horns so that it can see what it’s goring. Irritated by this carping – he had spent a lot of time on man – Zeus slings Momus off Olympus.

  In The Parts of Animals Aristotle alludes to Aesop’s fable, but his version has nothing about horn-eyes; instead Momus suggests that the bull should have had its horns on its shoulders since that’s where they’d be the most use. Aristotle retorts with plonking humour, ‘Momus’ criticisms here are obtuse.’ He should have done some research on the strength and direction of blows; besides, if horns were on the shoulders (or anywhere else) they’d impede the bull’s movements; they’re just where they should be: on the head.

  That’s a straightforward conditional-necessity-type teleological argument: horns are for protection, so they’re in the best possible position subject to other functional constraints. He adds some other details: how they’re hard, how in deer they’re solid, how in bulls they’re hollow but are strengthened by a bone at the base and so on. It’s all as adaptationist as can be. Again, you’d expect that when he turns to explaining why most animals don’t have horns, he’ll demonstrate how the lifestyles of some animals necessitate horns while those of others don’t. He doesn’t. Instead, he invokes a set of auxiliary principles that depend on the economics of the body.

  In the Politics Aristotle argues that household management reduces to two problems: command and control, and economics. It’s about who rules whom and about the acquisition and allocation of goods. He has a strong sense of the natural order of things. There is a natural hierarchy: master, wife, children, slaves, animals. There is – or should be – a natural limit to the acquisition of wealth. He’s very severe on the getting of money beyond one’s needs: retail is unnatural, usury loathsome. He has an intellectual’s contempt for the bourgeois’ money-obsession. His tone is that of a 1940s Cambridge don (F. R. Leavis springs to mind): autocratic, moralistic, puritanical.

  When writing of household economics he repeatedly refers to animals. When writing of animals he repeatedly refers to household economics. ‘Like a good housekeeper, nature is not in the habit of throwing away anything from which anything useful can be made’; ‘nature does nothing in vain’; ‘what nature takes from one place it adds to another’; ‘nature does not act out of cheapness’. Aristotle needs these principles to make his teleological explanations work, but he doesn’t argue for them, they are axioms whose truth is obvious. Heraclitus once said that ‘Nature loves to hide.’ Not from Aristotle. He writes as though nature is living next door and running a taverna.

  Aristotle is curiously ambivalent about the utility of horns and antlers. To be sure, animals have them for the sake of defence, but he also suggests that they’re dispensable or even deleterious. He’s impressed by the fact that stags shed their antlers annually. I also suspect that he never saw them in action. He speaks of their use against predators, the huntsman’s point of view, but not of their use as sexual weapons. He can never have seen the clashing antlers of deer in rut.*

  That horns aren’t very useful is reflected in their physiological origins. As animals build themselves from the nutrition they assimilate, they first construct the most vital organs using the highest-quality nutrition and then, if they have something left over, make the less important ones. Thus his ‘good housekeeper’ who, we have to imagine, has some scraps left over from the family meal that she throws to a stray cat skulking around the kitchen door – a cat that’s, frankly, a bit of a pest and you certainly wouldn’t want it in the house, but the children like it and it does help keep the mice down. Horns are like Greek cats: low in both cost and marginal utility.

  So why don’t all animals have horns? Aristotle gives two reasons. Consistent with his ‘good housekeeper’ image, he thinks that animals are efficiently designed in that they generally lack functionally redundant organs. He notes that animals can protect themselves by being big, fast, horned, tusked or fanged. But if an animal has one means of protection it does not need another, for ‘nature does nothing in vain or superfluous’.

  There’s another economic principle at work. In Historia animalium Aristotle has identified a web of associations among live-bearing tetrapods (mammals) including the fact that horned animals (ruminants) have an unequal number of teeth in their jaws (they’re missing canines and incisors in their upper jaws) where hornless animals (e.g. horses) don’t. Horns and teeth must be hard and so both have lots of earthen stuff in their mix. He accordingly argues that there is a trade-off between the making of horns and the making of teeth: an animal can make either horns or a full complement of teeth, but it can’t make both because, as he often puts it, ‘what nature takes from one place it adds to another’.* He wields this principle of resource allocation with great subtlety. He notices that the horns of large animals are disproportionately large compared to those of smaller ones, such as the gazelle, which is the smallest ruminant he knows, and explains this pattern by arguing that large ruminants have relatively more surplus earthy material to devote to their horns than smaller ones do. He’s touching on one of the great patterns that living things show – one that we are still hard-pressed to explain.*

  Although Aristotle’s nature is generally parsimonious, sometimes parsimony can be taken too far. Many animal organs have multiple functions; the elephant’s trunk is especially versatile. But he also observes that there are functional trade-offs. It’s hard to do many things well, so he generally holds that it’s better for parts to be specialized. As he puts it, nature doesn’t act ‘like a coppersmith who, out of cheapness, makes a turnspit and lamp holder in one’, which curious device presumably doesn’t work very well as either. He also supposes that more complex animals tend to have more specialized parts.

  These auxiliary principles pervade his explanations of diversity. Nature’s good housekeeping explains (or helps explain) the presence and absence of all sorts of weakly functional organs such as eyebrows, spleens and kidneys. That nature does nothing in vain explains inter alia why fish don’t have eyelids, lungs or legs, why fanged animals don’t have tusks, why only animals with molars grind their teeth from side to side, why our teeth last as long as they do and why males exist. The fact that nature can only give to one part what it’s taken from another explains inter alia why sharks don’t have bones, why bears don’t have hairy tails, why birds don’t have bladders, why lions have only two teats, why birds have either talons or spurs but not both and why the frogfish has its funny shape. It also explains much of life-history variation and why we die.

  Collectively these auxiliary principles are a model of the body’s economic design. Just as the master of a human household has a certain natural income out of which he must feed, shelter and clothe his charges, an animal has a certain nutritional income out of which it must build its parts and perform its functions. Some organs and functions are vital; others are useful but dispensable. Vital organs and reproduction have first call on nutritional income, and dispensable organs are made if there’s something left over. In general, however, animals operate under fairly severe budgetary constraints and organs are expen
sive. This has two consequences. First, the manufacture of some organ must often be paid for by an inability to make another. Second, animals must make efficient use of their nutritional income and so tend not to make functionally redundant organs. Although all animals have to keep within their nutritional budgets, larger animals have a disproportionately greater surplus than smaller ones and so can afford to allocate more nutrition to non-vital organs. Finally, although multifunctional organs are cheap, and many animals have them, the virtues of functional specialization mean that it’s best to have one organ perform a single task if possible.

  Aristotle doesn’t spell this model out. Nowhere does he speak of nutritional ‘income’, ‘efficiency’ or ‘budgets’. This is a model of his model, but one that makes sense of much of his auxiliary teleology. Economics is woven into the theoretical structure of modern evolutionary science; it has been so since Darwin. Darwin lived in an age of laissez-faire capitalism, belonged to the rentier class and absorbed Adam Smith and Malthus through his pores. Aristotle did not, yet I believe that he understood and applied these simple but profound economic truths too.

  THE

  SOUL OF THE

  CUTTLEFISH

  CUTTLEFISH EGGS ON A BRANCH

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  KALLONI’S FISHING BOATS are the small, double-ended kind called trehantiri, painted blue with trims of yellow and green. When we got to the harbour most of the fleet was still tied up. A pelican standing on the quay silently yawned and ruffled his feathers. The dawn Lagoon was very still, a reflected symmetry of grey-washed oranges, pinks and blues, bisected by a slash of white marking the western shore.