The Lagoon Page 30

  Developed? In what sense did tetrapods develop four feet? Why the dynamic language? Why not just say that this is the way they are? It’s not as though tetrapods are born walking upright, or that the world was once filled with cognitively crippled bipedal horses and sheep staggering about on their hooves. Presumably he’s speaking metaphorically. Still, you can see where this comes from. He had the recipe down pat; he had used it so many times. Take an idea from The Timaeus. Discard the moralizing. Add some common-sense biology. Present as science.

  XCIV

  IT IS SOMETIMES SAID that Aristotle could not have been an evolutionist for want of evidence. This seems plausible. There is one class of evidence that Darwin had, and had in abundance, that Aristotle apparently did not: fossils.*

  Aristotle did not know that in bygone ages the earth pullulated with creatures now extinct. He did not know that Lesbos and the Troad once looked – and, as these things scale, not so long ago – like the Serengeti with a fauna to match.* It is precisely such evidence, the argument goes, that was required before the theory of evolution could take wing. In November 1832, when Darwin arrived in Montevideo, Volume II of Lyell’s The Principles of Geology – the one about the fossil record, biogeography and the transmutation of species (arguments against) – was waiting for him in the post.

  Yet the argument is too simple. For, although Aristotle never mentions a single fossil in his works, or anything that can be construed as one, it is implausible that he knew nothing about them. More precisely, it is implausible that he was never confronted with prima facie evidence for the previous existence of life forms that were, in his day, at least locally extinct.

  A roll call of Greek travellers and physiologoi before, contemporaneous with and immediately after him described stony objects that resemble animal remains. Beds of seashells located in unlikely places were particularly likely to attract attention. Xenophanes reported shells from a mountain in Sicily. He also reported the imprints of fishes and other marine life in stone from Syracuse, Paros and Malta. Xanthus of Lydia (fl. 475 BC) saw beds of stranded seashells in Anatolia, Armenia and Iran. Herodotus, Eratosthenes of Cyrene (c. 285–194 BC) and Strato of Lampsacus (fl. 275 BC) all puzzled over seashells in the middle of the Egyptian desert near Karnak. That the sea must have once covered the land was obvious to them; they just disagreed how.

  FOSSIL SHELLS FROM CALABRIA

  In On Stones Theophrastus describes ‘dug up’ – oryktos – ivory.* He does not give its origin, but the megafaunal deposits of Samos, Kos or Tilos to the south-east of Lesbos seem like a good guess. The late Pleistocene through Holocene levels contain the remains of a dwarf elephant species that may have survived until four thousand years ago. The deposits have been known since at least the Archaic Period. In Samos, the bones of giant extinct animals were displayed, Wunderkammer-style, at a cult temple to Hera. Local myth had them as the remains of ancient monsters called ‘Neades’. A bone dug up near a seventh-century altar belonged to the extinct Miocene giraffe, Samotherium.

  Lesbos’ own megafaunal fossils are more modest. You can see them at the little natural history museum in Vrissa, a village just above the Lagoon. Kostas Kostakis, the caretaker, is particularly proud of the giant tortoise whose remains were found near Vatera. A life-size reconstruction made of fibreglass has the dimensions of a VW Beetle, but the fossils themselves are a bit disappointing. The whole thing has been extrapolated, no doubt accurately, in a Cuvierian fashion, from some leg bones, claws and scutes.

  No surprise, then, that Aristotle does not speak of giant, extinct Lesbian tortoises. But how did he miss the vast petrified forest that litters the island? In the pyroclastic hills west of the Kalloni, the trunks of extinct conifers, complete with root systems, emerge from the phrygana like sawn-off temple columns. In the little port of Sigri massive stone trunks lie on the beach. They have lain there, immovable, since they were felled by a volcanic eruption 20 million years ago. Aristotle says nothing about them; Theophrastus, too, is silent. In his Enquiries into Plants the latter mentions ‘petrified reeds’ from the shores of the Indian Ocean (bamboo? coral?), but of the petrified forest of Lesbos not a word. Yet Sigri is the next port over from Erresos, his home town. As a boy he could have played on those trunks. They, too, now have a museum, a glorious one.

  The mystery may have a prosaic solution. It may be that Theophrastus, at least, knew all about the petrified forest and wrote about it. Diogenes Laertius records a Theophrastan work that may have been titled On Things Turned into Stone. That suggests to us that it was about fossils, but we do not know, since Diogenes’ text is corrupt and an alternative reading is On Burning Stones, which is presumably about coal or volcanoes.

  Perhaps, then, it is not the fossils that are missing, just the texts. Alternatively, perhaps, Aristotle set aside reports of desert and mountain clams as fantasy. (Did not Herodotus also say that Egypt contained necropoli of winged serpents – that he had seen them?)* Or perhaps, to continue the excuses, Aristotle simply never got over to the far side of Lesbos. The hills were hot; he was a bad sailor; Theophrastus forgot to tell him about the stone trees. All this is possible. But I wonder whether he chose, deliberately, to ignore the reports or even the evidence of his own eyes. After all, if you believe in the eternity and immutability of organic kinds, it is just possible that you might dismiss a forest as a field of stones.

  XCV

  THAT THEOPHRASTUS MAY have written a book about fossils tantalizes. That is because he took the road that his teacher did not.

  The first steps are small. Discussing differences between cultivars – Thracian wheat, Egyptian pomegranates, Apulian olives and the like – Theophrastus recognizes that a plant is shaped by both what the seed gets from its parent and its environment. That’s quite conventional. But then he goes on to explain that when a cultivar is transplanted from one region to another it acquires, within just a few generations, a new nature:

  From this second source [differences in environment], moreover, arise peculiarities within kinds (that is to say varieties); and we often find that what was contrary to nature has become natural once it has persisted for some time and increased in numbers.

  This is very un-Aristotelian. It allows the boundaries of formal natures to shift. It also mingles the formal and material causes that Aristotle strives so hard to separate. But Theophrastus doesn’t let it rest there for he also argues that the cultivars found in different countries are ‘useful’. He means that Thracian wheat sprouts late because Thracian winters are harsh and that if you plant a seed in a new country it will eventually change to meet the challenge. Theophrastus’ plants aren’t perfectly adapted; they can improve. His vision of the world is also teleological, but where Aristotle’s world is frozen perfection, Theophrastus’ is contingent and in flux.

  He’s so modest, so plodding, so reluctant to propose big theories, that it’s easy to miss his most radical claim of all. Up till now, Theophrastus has just been talking about the origin of new varieties of wheat and grapes. If that’s evolution, then it’s evolution of a pretty paltry sort. But what about the origin of species? Can one kind of plant transform (metaballein) into another? Yes, says our botanist, looking up from the ground, it’s rather marvellous when it happens, but it definitely can.

  Wheat can transform into aira. These cereals, he says, are different kinds; you can tell them apart by their leaves. Some people doubt that one transforms into the other; they say that aira just happens to grow in wheat fields during especially rainy years. But, Theophrastus continues, the ‘best authorities’ agree that many people have sown wheat but reaped aira.

  Well, maybe. It’s not that Greek farmers didn’t sometimes sow wheat and reap aira, they probably did, but the explanation for this on the face of it remarkable event isn’t some lightning-bolt transformation. Aira is, as Theophrastus says, a totally different species, it’s a weed called darnel (Lolium temulentum) and the reason that a farmer might find his fields full of it is that its seeds look a lo
t like grains of wheat.* The transformation of wheat into darnel is, then, just the report of a farmer who failed to sort his seed stock and who, confronted with a field of toxic cereal, had to explain the fact away.

  But there is an unwitting truth to Theophrastus’ transformist claim. Darnel doesn’t mutate instantly into wheat, but the reason its seeds look so much like wheat grains is that they have evolved that way. Its history is written in the archaeology of the Levant. It’s been a weed since before Babylon; farmers were sorting it from their seed stock in the Neolithic. But sorting is selection and selection is, given heritable variation, evolution. Over millennia the weed has evolved to mimic the grain the better to escape the farmer’s sieve; by the fourth century BC it was a cuckoo infesting the seed banks of Europe. It took modern chemical herbicides to kill it off.

  Would Theophrastus have bought this evolutionary tale? Probably – after all, he accepts that transformation can happen in a single season. True, he’s uneasy about his wheat/darnel (it’s one of several ‘problems’ that he considers about the generation of plants), but, having convinced himself of the fact, takes it in his theoretical stride. He discusses the origin of the transformation and concludes that some sort of ‘corruption’ in the seed must cause the ‘starting point’ of the embryo to be ‘mastered’. This, he continues, is analogous to what happens when a female (animal), or something even more unnatural, is produced, for we must think of the ‘earth as a female’.

  He’s simply appropriated Aristotle’s theory of monstrosity to explain the evolution of one natural kind into another – and it is evolution even if it is still far from Darwin’s vision of a great tree of life. So often, when reading Aristotle, we sense the pressure of transformism. It is then that we should suspect that we are merely reading our own evolutionary preoccupations into texts that are, in fact, devoid of them. But the pressure must have been there, for Theophrastus, once his student, then his colleague, eventually his successor and, for more than twenty years, his friend, yielded.

  XCVI

  WILLIAM OGLE, WHO loved Darwin and Aristotle both, wished they could have met in person. In his letter to Darwin he imagines the Greek arriving at Down House. Aristotle considers Darwin with suspicion. He scans, as authors do, the study’s bookshelves for his own works. He is astonished, as authors are, to find them not there – as, indeed, they weren’t, Darwin having, by his own admission, long forgotten what little Greek he ever knew. He would also, continues Ogle, be astonished to discover that his views were of only antiquarian interest and that his old foe Democritus had triumphed; had, indeed, been reincarnated in Darwin. ‘I have, however, such faith in Aristotle as an honest hunter after truth’, writes Ogle, ‘that I verily believe that, when he heard all you have to say on your side, he would have given in like a true man, and burnt all his writings.’

  That seems optimistic. Aristotle would surely have scornfully pointed out that Democritus was oblivious to the appearance of design in nature, and – making the priority clear – have congratulated Darwin for placing final causes at the centre of his theory. He would have dismissed pangenesis as warmed-up Hippocratic theory and natural selection as a new label for Empedocles’ maunderings. He would have been right about the first and wrong about the second. He would have been enchanted by the biota of the New World and impressed by the fossils. (You can’t ignore a Megatherium.) Perhaps, upon reflection, he would even have granted that species evolve, that his grand vision of life’s order had been subsumed by a grander one. I like to think so.

  Were he to do so, he’d have to discard some of his metaphysics but, insofar as the two can be severed, not very much of his science. Theodosius Dobzhansky famously remarked, and evolutionary biologists endlessly repeat, that ‘nothing in biology makes sense except in the light of evolution’. The sentiment is a fine and ringing one, always handy if there’s a Creationist about, but it isn’t really true, for quite a lot does.

  Aristotle understands as Darwin did and we do that: (i) the complex morphologies and functions shown by living things require a primal source of order or information, his ‘formal natures’ or simply ‘forms’; (ii) that these forms are dynamic, self-replicating systems; (iii) that they vary among kinds to give diversity; (iv) that they exert their power by modifying the flow of materials in development and physiology; (v) that organisms gain these materials from nutrition which is transformed internally; (vi) that this material is limited in quantity; (vii) that the manufacture of parts, production of progeny, indeed survival itself, all expend this material – that is, are costly; (viii) that these costs limit the forms and functions of organisms such that if they do or make one thing it is at the expense of not being able to do or make another; (ix) that these costs are not absolute: some organisms are more subject to them than others; (x) that these material constraints act in concert with functional demands to give the diversity of animals that we see in the world; (xi) that the parts of animals are suited to the environments in which they live, that they are, in a word, adaptations; (xii) that the functions of different organs depend on each other – that is, living things must be understood as integrated wholes. Much of modern evolutionary science is in this list – but evolution isn’t.

  You may object that these similarities are superficial. After all, evolution is a dynamical theory and Aristotle’s world is static. But dynamics are difficult and so, when accounting for the features of animals, biologists often assume a world at equilibrium. What remains then for us, as for Aristotle, is an engineering problem, the search for the optimal solution in a set of possible solutions. ‘Nature’, he says, ‘does that which, among the possibilities, is the best for the being of each kind of animal.’ It is the engineer’s credo and the starting point for biomechanics, functional morphology, sociobiology and all the other sciences of organismic design. It is surely no accident that Aristotle established this principle, and declared it fundamental, in a book on the locomotion of animals.

  Although I have counterposed, as he does, Aristotle’s use of teleological and material explanation, he clearly thinks that usually there is no conflict between them at all. When explaining the association of parts he sometimes appeals to functional harmony, sometimes to bodily economics, but often ecumenically opts for both. Rays have cartilaginous skeletons because they need to be flexible given how they swim and because, having spent all their earthy matter on their hard skins, they don’t have anything left for the skeleton. Such double-barrelled arguments appear to be redundant, but in fact they’re not; they are merely missing an additional premise. For Aristotle, functional demands and the allocation of resources are harmonized because ‘nature does nothing in vain’. In their Principles of Animal Design (1998) Weibel and Taylor call this the ‘principle of symmorphosis’.

  The history of Western thought is littered with teleologists. From fourth-century Attica to twenty-first-century Kansas, the Argument from Design has never lost its appeal. Aristotle and Darwin, however, share the more unusual conviction that though the organic world is filled with design there is no designer. But if the designer is dead for whose benefit is the design? It’s the prosecutor’s question: cui bono?

  Darwin answered that individuals benefit. Biologists have batted the question about ever since. The answers that they’ve essayed are: memes, genes, individuals, groups, species, some combination or all of the above. Aristotle, however, generally appears to agree with Darwin: organs exist for the sake of the survival and reproduction of individual animals. This is why so much of his biology seems so familiar.

  Yet there is a deep difference between Aristotle’s teleology and Darwin’s adaptationism, one that appears when we follow the chain of explanation that any theory of organic design invites. Why does the elephant have a trunk? To snorkel. Why must it snorkel? Because it’s slow and lives in swamps. Why is it slow? Because it’s big. Why is it big? To defend itself. Why must it defend itself? Because it wants to survive and reproduce. Why does it want to survive and reproduce? Because
. . .

  Because natural selection has designed the elephant to reproduce itself. Darwin gave teleology a mechanistic explanation. He halted the march of whys. It is for this reason that Ogle celebrated Darwin as Democritus reincarnated. For, where Aristotle’s organismal teleology is imposed upon recalcitrant matter, Darwin showed how, given a few simple conditions, it emerges from it. Darwin is an ontological reductionist; Aristotle is not.

  Why, then, should Aristotelian animals strive to survive and reproduce? Aristotle can hardly invoke natural selection. (He’s dismissed at least one version of it.) He could have said ‘they just do’, and left it at that, but then he would not be Aristotle, so he does have an answer, beautiful and a little mystical. Living things, he says, desire to survive and reproduce so that they can ‘participate in the eternal and the divine’. When he asserts that living things desire to participate in the eternal he means that they are designed not to become extinct. Cui bono? It turns out that organismal design is not, after all, for the sake of individuals, for they always die, but to ensure that their forms/kinds, their species, persist for ever.

  When Aristotle speaks of the divine he is not – the point must be made again – invoking a divine craftsman for none exists; rather, he is telling us that immortality is a property of divine things and that reproduction makes animals a little bit divine.

  We are beginning to touch on Aristotle’s theology, his ultimate explanation for why the cosmos is arranged the way it is and its relationship to an immortal God. Why should animal kinds be immortal? This is where we come to the end of explanation, to one of those indemonstrable axioms that lie at the bottom of every Aristotelian science, and from which all else flows, and it is simply this: it is better to exist than not to exist.