The Lagoon Page 8

  The paper nautilus’ disposable penis-tentacle was an anatomical wonder of the nineteenth century. One that Aristotle, remarkably, had known all about. Or so, in 1853, claimed an enthusiastic von Siebold: ‘Vérany and Müller, who have produced a new phase in the history of hectocotylus, will learn with astonishment that Aristotle may fair contest with them for priority of the relation between the male octopus and the hectocotylus arm.’

  POLYPODON MEGISTON GENOS – COMMON OCTOPUS – OCTOPUS VULGARIS ABOVE: COPULATORY ARM OR HECTOCOTYLUS. BELOW: ADULT

  Could he? Aristotle certainly knew Argonauta argo. He calls it the nautilos polypous or ‘sailor’, describes it clearly and believes (‘though knowledge from observation is not yet satisfactory’) that it is not as firmly attached to its shell as other shelled animals such as snails and clams are. This is true, but he also repeats a story, that it uses the web between its tentacles as a kind of sail, and that is not. On its amours, however, Aristotle is as silent as the creature itself.

  Yet Aristotle did see something. Describing the mating habits of the octopus, he says that one of the male’s tentacles looks different from the rest, being pale, more pointed, with larger suckers at its base and a crease at its tip. During courtship, he continues, the male inserts this tentacle into the funnel of the female. In 1857 Steenstrup confirmed that Octopus vulgaris also has a penis-tentacle. It is a less outré version of Argonauta’s for when octopus male is done, he retrieves it intact from his mate’s orifices – but it is just as Aristotle describes it.

  Von Siebold exaggerated Aristotle’s anatomical prowess. Aristotle certainly spotted the subtle specialization of the octopus’ penis-tentacle, but he was unsure what it was for. In some passages he suggests that the tentacular probings are coitus itself; in others he says no, that’s a fisherman’s tale, the octopi are merely bracing themselves for sex. He cannot understand how semen can be transferred via a tentacle and doubts the whole business on a priori grounds. This approach, sound enough when considering fellating fish, led him astray on amorous octopi. But both passages tell us something about the way he thought. And, perhaps, that he wasn’t inclined to get his feet wet and watch them himself.

  XXVIII

  BUT THERE IS one discovery for which Aristotle deserves full credit. He described the remarkable embryos of the smooth dogfish.

  Observing that dogfish, sharks, rays and torpedo fish have cartilage where most fish have bone, he gives them a collective name, selakhē.* He knows that they have external genitalia and copulate but, once again, he’s cautious – ‘fishermen say’ – about how. He notes that some selakhē, such as the batides (rays or skates) and skylion (spotted dogfish), lay eggs with hard shells and tendrils – the ‘mermaid’s purses’ that can be found washed up on beaches – but that most give birth to live young. Moreover, he knows that if you cut a female akanthias galeos (spiny dogfish) open the foetuses can be seen still enclosed in their egg cases; they are, as we would say, ovoviviparous.* This was probably common knowledge. Nowadays the infants, which are known as koytabakia or puppies, are eaten with garlic sauce.*

  The selakhē are clearly strange fishes. But one selachian, the leios galeos, is stranger yet. Here:

  the animals develop with the umbilical cord attached to the uterus, with the result that as the eggs are used up the embryo resembles that of a tetrapod. A long umbilical cord is attached to the lower part of the uterus, each one fixed by a kind of sucker. The embryo is fixed to the cord in the middle, at the liver. The nourishment, in a dissected embryo, is egg-like, even when it no longer has the egg. A chorion and membranes grow round each of the embryos, as in tetrapods. When young the embryo has its head upwards, downwards when they are well grown and complete . . . This could not be clearer. Aristotle is describing the fact that the pups of the smooth dogfish, Mustelus mustelus, are linked to their mother’s uterus by an umbilical cord and a kind of placenta. He even notices that this remarkable arrangement is otherwise found only in live-bearing tetrapods – that is, mammals.

  LEIOS GALEOS – SMOOTH DOGFISH – MUSTELUS MUSTELUS PLACENTATION

  In the 1550s Pierre Belon and Guillaume Rondelet confirmed the smooth dogfish’s peculiar reproductive structures. The latter even figured an infant dangling by an umbilicus from its mother’s belly. In 1675 the Danish naturalist Niels Stensen (Steno) dissected one and showed how the umbilical cord feeds into its guts. After that the smooth dogfish was forgotten for nearly two centuries. Cuvier and Valenciennes do not mention it. Johannes Müller discovered it again in 1839. In a masterpiece of dissection, he showed that the placenta of the smooth dogfish is in fact the yolk sac that has become attached to the mother’s uterine wall and has a structure as elaborate as that of any mammalian placenta. In homage to his master he titled his monograph Über den glatten Hai des Aristoteles (On Aristotle’s Smooth Shark).

  Many zoologists have praised Aristotle, for they have seen him as one of their own. Some, in their enthusiasm, have ignored his defects; they have attributed to him their own insights and obsession with accuracy by way of compliment. However, one scholar and zoologist’s assessment seems to me particularly beautiful and just:

  Now I take it that in regard to biology Aristotle did much the same thing as Boyle, breaking through a similar tradition; and herein one of the greatest of his great services is to be found. There was a wealth of natural history before his time; but it belonged to the farmer, the huntsman and the fisherman – with something over (doubtless) for the schoolboy, the idler and the poet. But Aristotle made it a science, and won a place for it in Philosophy.

  Thus D’Arcy Thompson.

  NATURES

  KRANGŌN – MANTIS SHRIMP – SQUILLA MANTIS

  XXIX

  SCHILLER SAID THAT the Greeks saw nature without sentiment; Humboldt that they did not portray her for her own sake. I think that both are wrong.

  Cicadas cry softly under high leaves, and pour down

  shrill song incessantly from under their wings

  The artichoke blooms, and women are warm and wanton –

  but men turn lean and limp for the burning Dog-Star

  parches their brains and knees.

  Alcaeus’ lovely fragment may be about Lesbos, for that is where he came from. He wrote it in the sixth century BC and may have been Sappho’s lover. Perfectly capable of comparing a loved one’s face to a squadron of cavalry or the ranked oars of a battle-fleet, Sappho too wrote of golden broom by the seashore, the dew on wild roses and thyme, and how light pours on to the sea. And, if one reads further in the Greek Anthology, that compilation of broken odes and bittersweet epigraphs, it is clear that for the thousand-odd years of its span, nature was always near to the Greeks and filled with meaning.

  Yet there is sense, a narrow sense, in which Schiller was right. The Greeks may have also celebrated the swallow’s spring return but their ‘nature’ is not the Romantics’ nature, a catch-all for everything wild and inhuman. For the physiologoi it sometimes meant ‘creation’; at least Xenophanes, Heraclitus, Empedocles, Gorgias, Democritus and, later, Epicurus all wrote works titled peri physeos – On Nature – that contain cosmologies. Aristotle, too, wrote a work with that title (the first four books of his Physics), but it isn’t a cosmology at all. Rather, it is an analysis of change.

  Rocks fall, hot air rises, animals move, grow, copulate and die; the heavens rotate – all is in motion. We take it for granted that the causes of change are various. Steam rises from a cooking pot towards the sky and so does a plant growing in a garden, yet these phenomena are obviously so different that they must have different causes. Aristotle sees that too – though not in quite the same way that we do – but he also sees that change itself is the thing that needs to be explained, and so he identifies it with physis – ‘nature’. He says it would be absurd to try to prove that nature in this sense exists. Lots of things have natures – that’s just self-evident. The scientist’s job is to discover how nature works and what it is.

  He did not i
nvent this conception of physis for it can, perhaps, be found in Homer: ‘So saying, Hermes gave me the herb, drawing it from the ground, and showed me its nature.’ It’s certainly very close to Democritus: ‘Nature and teaching are similar, because teaching changes a man’s shape, and nature acts by changing shape.’ By descent it is also close to our use of ‘nature’ to describe the innate causes of something, as in this piece of doggerel by Isaac Watts (1674–1748), ‘Let dogs delight to bark and bite / For God hath made them so; / Let bears and lions growl and fight, / For ‘tis their nature too,’ or Hobbes’ ‘Nature (the art whereby God hath made and governes the world)’.

  But Aristotle isn’t an eighteenth-century deist, and dragging God into the causal chain risks obscuring what he means. His nature is an internal principle of change and rest. That’s the fundamental difference between natural objects and artefacts: the former move and stop by themselves; the latter don’t and can’t. And, although he thinks that inanimate natural things such as elements also move of their own accord, it’s plain that this definition of ‘nature’ is really built for biologists. Its purpose is to pin down the mysterious way in which creatures do all that they do – and do it by themselves. No one cranks the clockwork, no one points the little machine in the right direction – nature does.

  XXX

  IN DEFINING NATURE AS an ‘internal principle of change and rest’, Aristotle merely delimits the scope of natural science. The question – the great question that motivates his entire scientific enterprise – is what are the causes of change?

  To answer this question Aristotle began to read. By the time he arrived at the Academy in 367 BC, the intellectual tone was anti-scientific and the great line of physiologoi extinct. But their books – papyrus scrolls – were still around. I won’t venture to say how or when Aristotle retrieved them from the library shelves; I note only that when he left the Academy he was thirty-seven, so he’d had plenty of time to read, take notes and think.

  Among the works that he read were Democritus’. Only Plato looms larger in Aristotle’s intellectual hinterland than he. The natural philosopher’s natural philosopher, Plato is said to have loathed him and wished his books burnt. Later philosophers evidently read them, so we know that he did not destroy them; yet posterity has granted Plato his ignoble wish for not one now exists. Aristotle’s physical theory is constructed largely contra Democritus’, but much of what we know about the latter comes from the former for, unlike Plato, Aristotle paid his opponents the compliment of preserving their words.

  As Aristotle tells it, Democritus held that the world was ultimately composed of entities that were invisible, solid, indestructible, indivisible, immutable, infinite in number and variety and perpetually in motion – in short, atoms. He called his atoms onta – ‘things’. He learnt the theory from his teacher Leucippus. Today he and Leucippus are jointly celebrated as the fathers of atomic theory and all that it entails, for the theoretical thread that connects them to Dalton and Rutherford is, however etiolated, real.

  Democritus developed his atomic theory into a cosmology. The theory, which is sketchy – though whether due to Democritus’ failures or to history’s vicissitudes we do not know – proposed that atoms floating in the void collide with, and adhere to, each other and so form larger entities, ultimately the planets and stars. He also apparently explained sex determination, sensation and movement in animals by appealing to the shapes and motions of atoms. He may have elaborated a whole reductionist theory of life – the doxographers list three books on the Causes of the Animals – but we do not know since they are lost. Even so, the general thrust of his theories is clear. When Democritus sought to explain the nature of things, why they change, he appealed exclusively to matter – the stuff of which they were made. He was not the first to do so; materialism is one of the great threads of Neo-Ionian speculation, but his account was the most sophisticated. Aristotle would spend much of his life trying to show why it is wrong; in a way his scientific works are one long argument against the materialists. We have arrived at one of the great turning points of scientific thought. It’s often been judged a wrong turn.

  The problem with Democritus’ cosmology, Aristotle argues, is that it has the universe arising spontaneously from atomic collision. To explain why this is improbable, Aristotle analyses the meaning of ‘spontaneous’. Suppose, he says, we see a tripod standing on its three feet, we would naturally suppose that someone had deliberately placed it so. But that need not be the case; perhaps the tripod fell from a roof and just happened to land on its feet – the Greek is automaton from which our ‘automatic’ comes. Democritus supposes that the cosmos is like a tripod standing on its feet, one that wasn’t put there deliberately, but just happened to land so.

  It seems like a peculiar argument. Why shouldn’t the cosmos just happen to have landed on its feet? But Aristotle’s point is that spontaneous events are those that appear to have a purpose but in fact don’t. And that is the nub of the matter: Aristotle thinks that the cosmos – the stars, the planets, the earth, the living things it contains, the elements themselves – obviously have a purpose; they show the hallmarks of design. And although purposeful things can arise spontaneously it just seems implausible to him that a cosmos that is so exquisitely ordered could spontaneously self-assemble.

  Most modern cosmological theories suppose that the universe does not have a purpose but just is. Only a child would ask ‘what are the stars for?’ But that’s not a childish question to Aristotle. His sense of purpose embraces almost everything. Perhaps this will seem less strange if we see him as a kind of cosmic biologist. We may think that he’s on uncertain ground when looking at the stars, but he’s obviously right to argue that the random collisions of atoms can’t explain the regular and purposeful features of life on earth (or anywhere else).

  Aristotle’s biologist’s vision of the world is explicit when tackling another of the physiologoi. Whenever he discusses Democritus, Empedocles is usually close by. For Aristotle, they are both materialists, albeit of different stripe. Empedocles thought that the world was composed of four basic elements – earth, water, air, fire – which can be read as matter in its solid, liquid and gaseous phases, with fire as an extra. These elements combine in particular proportions to give all the different kinds of stuff – stone, iron, bone, blood – that we see.

  Existing things have no nature – only a mixing and a separating of what has been mixed. Nature is a name given by human beings.

  ‘Nature’ is just mixology. Empedocles’ verses explain how a conflict between Love and Strife brings about the cyclical creation and destruction of the world and, with it, the periodic creation of living things. In the first phases of each cycle Love forms tissues, each to a particular chemical recipe, and from these tissues strange creatures emerge composed mostly of single organs: ‘eyes without faces’, ‘heads without necks’ and ‘single limbs’. Love waxes, Strife wanes, the cycle turns, body-part creatures fuse together in random combinations to produce creatures that have two faces, two chests, or else are part male and part female, or else are hybrid ‘man-faced ox calves’ or ‘ox-faced men’ – a teratological bestiary complete with a Minotaur. And it may seem that Empedocles is far from being able to produce the animals that we actually see except that he has a brilliant solution. Simplicius, a sixth-century AD commentator on Aristotle’s Physics, tells us what it is:

  Thus Empedocles says that under the rule of love parts of animals first came into being at random – heads, hands, feet and so on – and then came into combination: ‘There sprang up ox progeny, man-limbed, and the reverse [obviously meaning human progeny with oxen limbs, i.e. combinations of ox and man]. And those which combined in a way which enabled them to preserve themselves became animals, and survived because they [the parts] fulfilled each other’s needs – the teeth cutting and grinding the food, the stomach digesting it, the liver converting it into blood. And the human head, by combining with a human body, brings about the preservation of
the whole, but by combining with the ox’s body fails to cohere with it and perishes. For those which did not combine on proper principles perished. And things still happen the same way nowadays . . .

  Most of the recombinants were unfit and perished, so we see only the survivors today. Many early natural philosophers, Simplicius remarks, had this idea. That, if true, is remarkable, for it suggests that in Aristotle’s time the idea of selection as a source of order was a commonplace. Certainly Epicurus, a generation younger than Aristotle, gave an even more elaborate selection-based cosmogeny than did Empedocles – at least he did if Lucretius’ Epicurean verses are to be relied on.

  One might expect Aristotle to like Empedocles’ model. The Sicilian has – at least as Simplicius tells it – a perfectly reasonable mechanism capable of producing complex, functional creatures out of chaos. Surely Aristotle, seeking an explanation for purpose in nature, would see, and seize upon, this? He certainly sees the force of the logic. He picks a lovely bit of biological design: teeth. In infants, the front teeth – incisors – come up sharp fitted for tearing food while the molars emerge broad and useful for grinding food. Why, he asks, shouldn’t we view this as the product of a process in which things that are fittingly ordered survive and those that aren’t don’t? Why aren’t teeth ‘spontaneous’?