Thinkers who pondered the mysteries of nature used to be known as ‘natural philosophers’. For centuries there wasn’t a separate term for those few individuals who practised science (scientia, ‘knowledge’) in the sense of devising experiments and testable explanations and predictions in order to understand experienced reality. In 1833 William Whewell, a professor of mineralogy, created the term ‘scientist’ – by analogy with ‘artist’ – at a meeting of the new British Association for the Advancement of Science, to identify empirical thinkers who used all their senses and actually got their hands dirty in an effort to comprehend nature. ‘Science’ soon came to mean a methodology, a disciplined, systematic way of observing, studying and explaining the world. But in fact the ‘scientific method’ was first practised by Aristotle, whose works on natural history – including his grand treatise on comparative zoology, the History of Animals – are the subject of Armand Marie Leroi’s new book. Aristotle may be most famous for his Physics and Politics, but his most voluminous writings were biological. Leroi celebrates him as the first truly scientific thinker, in a modern sense: the first to observe, describe and attempt to classify biology systematically, in all its grandeur and myriad forms.
After Plato died in 348 bc, Aristotle left Athens for western Anatolia and took to the field, grounding his subsequent biological studies in deductions based on observation. In the Physics, he had maintained that the principles of change were teleological, that all things in nature moved towards achieving perfection of their potentials. The teleology is still there in the History of Animals and the other biological writings, but what’s new is an empirical approach based on data obtained from many sources: not only his own observations and dissections but also the reports of previous writers and information relayed by farmers, fishermen, sailors, hunters and travellers. Despite his interest in the principles of change and his awareness of transformation, mutation and deformity, his acceptance of the ‘fixity of species’ meant that, as Leroi puts it, ‘Aristotle never made the evolutionary leap.’
Aristotle’s blindspot was severely magnified by European Christians in the Middle Ages. The medieval insistence on divine creation and unchanging species eclipsed Aristotle’s innovative biological methodology, leading modern scientists to reject or misunderstand his important contributions. Today’s students of the animal and plant kingdoms, enriched by the wealth of ever accumulating fossil evidence and informed by scientific theories of extinction and evolution, seek to know how each species flourished and then either vanished or evolved over eons to become what they are in their present time and place. Leroi shows that Aristotle may have come close to expressing a principle of evolution in his ‘dynamic language’ about quadrupeds in Parts of Animals and his radical ‘version of natural selection’. But the rocks and earth that contained the evidence of extinct, evolving life forms, being inanimate objects, had no place in Aristotle’s typology of living beings.
In Athens, Aristotle would eventually found the Peripatetic School of Philosophy, in which walking and thinking – meditating while meandering – were intimately entwined. But before that, most of his wandering took place around Kolpos Kalloni, a large inland lagoon connected to the Aegean Sea on the verdant island of Lesbos. Leroi, an evolutionary biologist and ardent admirer of Aristotle, was drawn to retrace his route from Athens to Assos on the Turkish coast, and from there across the narrow strait to Lesbos where the nutrient-rich, calm lagoon harboured an abundance of salt and freshwater fish, eels, shellfish and other sea creatures, its marshy shores home to a chorus of birds, frogs and insects. The life flourishing in this sheltered pool was a boon to Aristotle’s decision to favour observation over Plato’s abstract speculation, and inspired his grand endeavour to catalogue, describe and explain the biological world as he found it.
It’s easy to imagine that the Lesbian lagoon, and Plato’s charming image for Greeks clustered around the Aegean Sea ‘like frogs or ants around a pond’, weren’t far from Aristotle’s mind when he applied his powers of taxonomy and explication to human beings, the most political of animals. Aristotelian concepts of advantageous social behaviour anticipate modern sociobiology. ‘The Politics is, inescapably, political science written by a biologist,’ Leroi writes. In his discussion of laws and servitude as set out in the Politics, he draws attention to Aristotle’s disturbing theory of ‘natural slavery’. Leroi grew up in apartheid South Africa, ‘a state founded on the notion that Africans were, by nature, incapable’ – in other words, that they were ‘natural slaves’ as described by Aristotle. He points out that doctrines of inherent incompetence and social difference have remained unresolved since antiquity. Political ironies, Leroi concludes, ‘haunt’ Aristotle’s Politics.
Such ironies hover too over portions of The Lagoon. One example is Leroi’s description of Aristotle’s Athens. In a book that cites so many up-to-the-minute social scientists and current biological advances, it is jarring to hear Leroi echo 18th and 19th-century anti-democratic sentiments: ‘The Athenian way of government [and] public life in fourth-century Athens was squalid. Every citizen could go up to the Pnyx and vote on the legislation of the day.’ The result, Leroi maintains, was endemic corruption and ‘mob rule’ by ‘rabble’ and demagogues. This antiquated picture of what today’s historians and political scientists generally consider Athens’s golden age of democratic prosperity and political egalitarianism has gathered two centuries’ worth of dust. Inexplicably, Leroi’s sole source is an 1872 history of Greece by Jacob Burckhardt, a fierce Swiss contrarian who detested Athenian democracy and glorified aristocracies (and Sparta).
Leroi also misses the opportunity to illuminate a lost chapter in the history of science. Some of the first inklings of the ‘scientific’ impulse can be traced back before Aristotle to ancient Greek discoveries and interpretations of petrified remains of the long-extinct creatures that once populated the Mediterranean world. This underappreciated body of evidence doesn’t constitute formal science, of course, but the numerous ancient accounts of remarkable plant and animal fossils do demonstrate careful observation and measurement, and rational attempts to explain evidence as it accumulates over time – crucial ingredients of scientific inquiry. One palaeontological puzzle the ancients solved was the presence of fossilised seashells and fish skeletons on mountains and deserts far from the sea. Because these marine fossils resembled known, living species, the explanation required no supernatural or divine forces, or the difficult concepts of extinction or evolution. All that was needed was a vision of land once submerged under the ocean to explain how marine creatures came to be stranded so long ago that they turned to stone. In the sixth century bc the natural philosopher Xenophanes was the first to articulate the idea that impressions of seashells, fish and seaweed observed in rocks in Italy, Malta and on the Aegean island of Paros had been trapped in mud that hardened in the remote past. Xanthos of Lydia (fifth century bc) arrived at the same conclusion to explain scallop and other shells found far inland, in Asia Minor, Armenia and Iran. By the time of Herodotus this understanding of shells and fish marooned by receding seas had become general knowledge.
Aristotle knew the writings of Xenophanes, Xanthos and Herodotus, and he had examined and dissected countless fish and marine creatures. Like Plato, he envisioned the cycle of sea transgressions and emerging land formations shaping the earth over eons. Fossil shells embedded in stone appear everywhere in the Greek world; they were typically seen in quarries. Many Greek buildings were constructed of highly fossiliferous ‘shelly limestone’ blocks dense with recognisable brachiopods, crinoids, sponges, molluscs and corals. Moreover, fish fossils are common on Lesbos. Yet, as Leroi remarks, Aristotle ‘never mentions a single fossil in his works, or anything that can be construed as one’. (In Parts of Animals, Aristotle alludes to petrifaction from drying exhalations of the earth but he seems to treat it as a myth. After an animal’s death, he writes, ‘nothing remains except the configuration, like the animals in folktales that are turned to stone.’) Not only did Aristotle overlook fossil fish but he also ignored fossilised plants, trees, and the femurs, scapulae, ribs, skulls, vertebrae, tusks and teeth of long extinct ancestral elephants, rhinos and other mammals of the Miocene through to the Pleistocene. These fossils continually came to light throughout the Mediterranean region, in Greece, Italy and North Africa, on many Aegean islands, and in western Asia Minor. We know this because about a hundred accounts by more than thirty ancient Greek and Latin authors tell how the petrified remains of unknown creatures were revealed by erosion, storms, floods, earthquakes and human digging. Great excitement surrounded the discoveries, as people journeyed to view the bones and measured the skull capacities of beasts never seen alive. Speculating on what they had looked like and the cause of their death en masse, people identified the creatures as the giants, monsters or heroes described in myth and legend. Greek sources say the fossils were displayed in temples or in situ all around the Mediterranean. According to Euagon, a fifth-century BC historian of Samos, for example, one could view the bones of titanic creatures called Neades on the island; the monsters had been destroyed long ago and trapped under rock by earthquakes. Aristotle cited Euagon on the tremendous Neades but didn’t mention their physical remains on Samos.
Leroi’s discussion of Aristotle’s sources is a fascinating survey of ancient biological writings available in the fourth century bc. We learn that Aristotle drew on his own experiences and the expertise of fellow scholars, often disputing their reasoning. Unlike Thucydides and Plato, however, Aristotle also valued folk knowledge. He combed through myths and local lore, gathered oral traditions, and solicited material from ordinary people, seeking nuggets of truth. This makes his omission of marine and mammalian fossils all the more startling. ‘It is implausible that he knew nothing about them,’ Leroi concedes. But Leroi’s excuse – ‘Aristotle did not know that in bygone ages the earth pullulated with creatures now extinct’ – seems weak. All around the Mediterranean, ordinary folk and other writers were interpreting fossil remains as proof that in bygone ages the earth did pullulate with giant creatures that no longer existed.
Like other modern historians of palaeontology, Leroi underestimates the opportunity Aristotle had to hear about, see and touch gigantic stone bones. He describes the megafaunal remains Aristotle saw in a small museum on Lesbos as ‘modest’, mentioning only giraffes, a ‘dwarf elephant’ and large tortoises, and seems unaware of the immense size of the many species of mastodons and mammoths, whose tusks, thighbones and shoulder blades towered over the Greeks who found them. In about 560 bc, for example, the Spartans excavated a colossal skeleton from a blacksmith’s well dug in Tegea. Herodotus recorded the dimensions, which match those of a mastodon or mammoth, common fossils in that region. The bones were hailed as the remains of Orestes and transported to Sparta with great fanfare. Kimon made an expedition to Skyros to retrieve the huge bones of the legendary Athenian king Theseus; these were placed in a shrine in Athens. Other cities sought out similarly impressive fossils to honour as the bones of their founding heroes. Meanwhile, in the temple of Tegea, Greeks could view a great, curved tusk of a woolly mammoth, said to belong to the giant ‘Calydonian Boar’ of myth, and in Olympia, they could marvel at the shoulder blade of the local hero Pelops, three times the size of a human scapula. At least two extensive fossil deposits in Greece, in Megalopolis and Chalkidiki, were so dense with jumbled, disarticulated limb bones of Ice Age megafauna that they were said to be battlefields where the gods had destroyed multitudes of giants and monsters.
Modern palaeontological and archaeological evidence confirms ancient fossil finds. In 1988 German archaeologists discovered a very large fossil femur among the sixth-century bc dedications at the altar in the Temple of Hera on Samos. American archaeologists recovered a similarly sized femur of an Ice Age woolly rhinoceros from the ancient acropolis at Nichoria in southern Greece; it had been brought there from the Megalopolis beds. A mammoth tooth was recovered from the ruins of Hippocrates’ medical school on Kos. A Greek vase from the sixth century bc depicts a monstrous skull emerging from a sea cliff near Troy. Aristotle had travelled to Assos; the region’s megafaunal remains were rich. Lesbos boasted fossil traces of sabre-tooth cats, giraffes, rhinos, mastodons and mammoths weathering out of sandy clay soil a few miles south of Aristotle’s lagoon.
Aristotle’s silence on all this is bewildering, but as Leroi points out, even more astonishing was his failure to take notice of the plant fossils abounding on Lesbos. ‘How did he miss the vast petrified forest that litters the island?’ In the hills a few miles west of the lagoon, Leroi notes, is a petrified Miocene forest. There are huge palm trunks and sequoia trees, many still upright, with pine cones and roots. In his informative discussion of Aristotle’s friend and successor, the botanist Theophrastus (c. 372-287 bc), Leroi suggests a credible reason for Aristotle’s silence on plant fossils. A native of Lesbos, Theophrastus had grown up in the midst of the island’s petrified forest. His writings describe mottled fossil ivory tusks dug up from the earth, petrified reeds from India, the mineralisation of organic objects, and fish embedded in rocks near the Black Sea. Some of his works survive – he wrote On Plants and On Stones – but others are fragmentary. Could the answer lie in the missing texts? Did Aristotle set fossils aside because his friend Theophrastus had covered both plant and animal fossils in work that hasn’t survived? This was the hunch, as Leroi notes, of Diogenes Laertius, a biographer in the early third century ad. But much stronger support for the notion can be found earlier, in the first century. According to Pliny, Theophrastus wrote about ‘stones shaped like bones that are found in the earth’ in a two-volume treatise titled On Petrifactions, which was lost after Pliny’s day.
Leroi concludes that Aristotle’s belief in the eternal immutability of organic life forms led him to dismiss the fossil evidence. But the question deserves deeper examination, especially by a modern historian of evolutionary biology and mutant life forms. What was it about fossilised organic remains of unfamiliar creatures of outrageous stature that denied them a place in Aristotle’s worldview and led him to pass over them without comment? Aristotle’s system was based on current living species, with no provision for anomalies, ‘mistakes in nature’, no longer extant forms or creatures that resisted categorisation, such as the bizarre sea monster types observed by fishermen and sailors. Aristotle labelled such rarities as monstrous and irrelevant to his investigations because they violated principles of ‘order and purpose’. He was not the only natural philosopher blind to the ‘folk science’ of fossils. Even though popular interpretations of stone bones were based on observation and produced coherent concepts that anticipated modern theories of deep time, geomorphology and extinctions by catastrophe, the insights were often expressed in mythological terms, which natural philosophers tended to shun.
The only modern scientist to recognise the significance of the long forgotten fossil discoveries of classical antiquity was the French father of palaeontology, Georges Cuvier (1769-1832), who studied them in developing his path-breaking theories of evolution and extinction. For the rest, however, the treasury of empirical folk knowledge of fossils preserved in classical literature has been rejected as superstitious trivia. After all, the excuse is made, Aristotle himself, with his insatiable curiosity and sweeping knowledge of everything under the Mediterranean sun, said nothing about fossils. But in fact his silence remains a mystery, which Leroi does not clear up.
None of this detracts from the magnificence of Leroi’s paean to Aristotle and the profound significance of his endeavour. Aristotle’s predecessors, Leroi notes, ‘viewed the world as if from Olympus … speculation filled in what they could not see.’ But Aristotle went down to the shore. He devised a robust ‘research programme’ in which ‘he observed, applied his causes to his observations and wove them together in the books that make up his Great Course in Zoology.’ The Lagoon is part personal memoir/travelogue, part long overdue festschrift for a cherished mentor, a ‘tribute to the power’ of Aristotle’s mind.
Aristotle, Leroi comments, ‘could not have conceived just how vast the science that he founded would become’. But in comparing ‘the elaborate tapestry of his science’ to our own, Leroi maintains that we can only now ‘see his intentions and accomplishments more clearly than any previous age has seen them’, and that is perhaps because we have finally ‘caught up’ with Aristotle, the man who ‘invented science from scratch’. One of the fascinating features of The Lagoon is Leroi’s ability to account even for Aristotle’s wildest misconceptions, so that we can understand exactly how and why the methodical, commonsensical scientist got some things so very wrong. With Leroi, we end up feeling that, had he time and world enough, Aristotle himself could have corrected his own mistakes.