Evolution

The Remarkable History of a Scientific Theory

by Edward J. Larson

Evolution

Hardcover, 337 pages, Random House Inc, List Price: $22.95 | purchase

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  • The Remarkable History of a Scientific Theory
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Book Summary

Traces the history of evolutionary theory, from the eighteenth-century emergence of paleontology, through the breakthroughs of Darwin, to the backlash against evolutionism, to its resurrection through the science of genetics.

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Excerpt: Evolution

Evolution

CHAPTER 1

Bursting the Limits of Time

Georges Cuvier had a large head-a famously large head-and an ego more than sufficient to swell even it. From his position atop the French scientific establishment during the first third of the nineteenth century, he accumulated high academic posts and official honors like some favored children collect toys: never enough and all kept in play. For his contributions to laying the foundations of modern biology, Cuvier willingly suffered comparisons to Aristotle, the acknowledged founder of the science. As a naturalist, Cuvier fancied himself "the French Newton"-bringing order to the life sciences much as Isaac Newton brought order to the physical sciences. Cuvier's rigorous empirical methods opened windows into the earth's biological history that would lead others to a vision of organic evolution he steadfastly refused to see. More than any other naturalist, he so greatly influenced the style and substance of nineteenth-century biology that the history of the modern scientific theory of evolution rightly begins with him-its staunchest foe.

Born in 1769 into an educated, bourgeois family in the Protestant, French-speaking portion of the independent French-German duchy of Württemberg, Cuvier was trained at a regional academy to serve in the duke's government. Pushed by his mother to excel academically, Cuvier's formal education included a solid introduction to natural history, a traditional subject encompassing such modern fields as biology, geology, oceanography, mineralogy, and paleontology. This subject became his passion. In 1788, with no government position open to him at home, Cuvier accepted employment as a private tutor for a French noble family in Normandy. There, as a sideline, he immersed himself in the study of marine invertebrates. From the relative safety of rural Normandy, Cuvier witnessed the French Revolution that began, from his perspective, with high hopes in 1789 but turned terribly ugly during the early 1790s. Becoming a citizen of France in 1793, when the French government annexed his homeland, Cuvier accepted a post in the revolutionary administration of Normandy even as he turned viscerally against the central regime's Terror and focused his own attentions on zoological fieldwork. In 1795, when a moderate republican government took power in Paris and promised to rebuild the central scientific establishment decapitated during the Terror, Cuvier moved to the capital in search of a career in science. There were plenty of openings for a naturalist of his obvious brilliance and driving ambition. Cuvier gained an assistantship at the renowned Museum of Natural History, and never looked back. His subsequent rise was meteoric. The study of natural history would never be the same.

Cuvier concentrated his scientific research on the burgeoning field of comparative anatomy; he was convinced that the internal structure of an animal revealed its function and therefore its true nature. In biology as in all else, form followed function for Cuvier. His research profited greatly from his position at the world's premier natural-history museum-an institution that rapidly became ever more comprehensive in its zoological holdings as Napoleon's armies plundered the collections of Europe and sent home live, preserved, and fossilized specimens from as far afield as Russia and Egypt. Ultimately, Cuvier proposed that there are four (but only four) basic anatomical types (he called them "embranchements") of animals: vertebrates (with backbones), molluscs (with shells), articulates (such as insects), and radiates (such as starfish). "Lesser divisions," he wrote, "are only modifications superficially founded on development or on the addition of certain parts, but which in no way change the essence of the plan."1 This view, built solidly on anatomical analysis and still reflected (with modifications) in modern taxonomy, shattered the hierarchical concept dating from Aristotle of a single great chain of beings rising in fine gradations from the simplest living form to humans at the top. The idea within biology of giving an anthropomorphic order to all living things gave way to studying them on their own terms.

Cuvier was the first naturalist to have at his disposal a suitably complete collection of the world's mammals-past and present-to make definitive distinctions among them. He made the most of this advantage, hoarding it to himself, his collaborators, and his protegés. In 1796, for example, he announced that, based on his anatomical comparisons of actual specimens, the elephants of India and Africa constituted two distinct species, and that both of them differed from the elephant-like mammoth found only in fossil remains. The positive identification of other living and extinct mammals followed one after another in rapid succession. To account for so many extinct species, as early as 1796 Cuvier announced "the existence of a world previous to ours, destroyed by some kind of catastrophe."2

Before Cuvier, European naturalists typically held that no species-all of them perfect in their original creation-ever died out. Fossils had no fundamental significance: Such things were simply sports of nature or remnants of some still-living species. Overturning this view, Cuvier ultimately concluded that all fossilized animals differed in kind from modern ones and that no modern species existed in truly fossil form. He boldly claimed the power "to burst the limits of time, and, by some observations [of fossils], to recover the history of the world, and the succession of events that preceded the birth of the human species."3

Suddenly, life had a history different from the present, and fossil fragments revealed it. "As a new species of antiquarian," Cuvier explained, "I have had . . . to reconstruct the ancient beings to which these fragments belonged; to reproduce them in their proportions and characters; and finally to compare them to those that live today."4 The modern science of paleontology was born in Cuvier's laboratory. Because of his conviction that the form of any animal precisely served its functional needs, Cuvier confidently assumed that trained researchers could, in principle, reconstruct its entire structure from any one of its functional parts. Paleontologists could do for extinct animals what comparative anatomists did for living ones-definitively identify them. Doing so for all of the earth's past and present species became Cuvier's goal for science-and he himself would launch the effort, doing his own best work with fishes and four-footed mammals.

A compulsive worker, stern and impatient, Cuvier never doubted his own ability as a science researcher, educator, and administrator. He mastered the treacherous shoals of French academic politics just as ably as he mastered comparative anatomy. Even as he climbed the professional ladder within the Museum of Natural History, Cuvier gained leadership posts at the National Institute and the University of France-giving him unparalleled influence over patronage within the country's highly centralized science establishment. Napoleon named Cuvier to the Council of State in 1813, and he deftly kept his seat (and steadily expanded his portfolio) under three succeeding monarchs. Remarkably, even though every ruler he served was forcibly driven from office at least once, Cuvier held each of his official posts for life and died peacefully in his bed in 1832.

Napoleon ennobled him as a chevalier; Louis XVIII promoted him to the rank of baron; under Charles X, he became a grand officer of the Legion of Honor; Louis-Philippe made him a peer of France. "Cuvier was short and during the Revolution was thin," one biographer wryly noted. "He became stouter during the Empire; and he grew enormously fat after the Restoration."5 Still there was that massive head, crowned with a thick mane of hair. According to one observer, Cuvier's head "gave to his entire person an undeniable cachet of majesty and to his face an expression of profound meditation."6 Here was the lion of nineteenth-century French science and founder of modern comparative anatomy and paleontology. Yet his reasoned scientific arguments for the theory of special creation held back the tide of evolutionary thought, which had been rising since the Enlightenment, for a generation.

On the matter of organic evolution (or "the transmutation of species," as the concept was then called), it was not simply that Cuvier died before the publication of Charles Darwin's Origin of Species and therefore never seriously considered the idea. He studied it carefully (albeit not in the light of Darwin's later arguments for it) and found it wanting. Although Cuvier's conclusions on this score reflected his religious and social beliefs, they were founded on his scientific understanding of nature. These added factors-religious and social-

reveal telling aspects of pre-Darwinian Western thought about biological origins. They will be examined first.Living in a particularly volatile era of French religious history characterized by alternating phases of Enlightenment scepticism, Revolutionary atheism, and Restoration Catholicism, Cuvier stood apart from most others within the cultural elite of France by remaining a churchgoing Protestant during his entire life. Indeed, he visibly aligned himself with his religious minority by overseeing government programs for Protestant education and serving as vice president of the Protestant Bible Society of Paris. He married a socially prominent Roman Catholic widow of the Terror, Anne Marie Coquet du Trazail, but they raised their children as Protestants. When his daughter Clémentine adopted an evangelical form of Protestantism, however, she grew to doubt her father's salvation and prayed for his conversion. That was not about to happen, at least on her terms. By definition, evangelicals publicly proclaim their religious beliefs and seek to convert others. But for Georges Cuvier religion was a strictly private matter. Perhaps it had to be so for him to prosper in French science and politics, but that lends an unjustifiably cynical slant to Cuvier's case. Although he was the very embodiment of reason in science, Cuvier accepted religious truth as existing wholly apart from reason. This made his private religious beliefs virtually invisible to others; despite considerable speculation, they have remained so to this day. Yet surely he was a Bible-believing Christian of some sort, and biblical Christianity carries with it certain presuppositions about origins. These presuppositions informed Cuvier's thinking about evolution just as they would for so many other Christians.

The biblical account of creation appears in the book of Genesis, which is sacred scripture for Jews, Christians, and Moslems. For the orthodox, Genesis represents the revealed word of God and, as such, carries special meaning in some literal, allegorical, or mystical sense. Even for liberal theists, led during the nineteenth century by a growing number of German and French theologians whose work Cuvier read, the Genesis account carries meaning as an early record of the Jewish people's understanding of God's role in Creation. Indeed, for those like Cuvier who accepted Moses as its author, Genesis gains authority as one of the earliest written records of creation. Accorded any of these meanings, the Genesis account becomes foundational for one's understanding of nature.

The first chapter of Genesis tells of God creating the heavens and the earth, then plants and animals, and finally humans-everything in six days. All types of plants and animals are said to reproduce "according to their kind." Read literally, this precludes evolution from one "kind" of plant or animal to another. Regarding humans, the account declares that God separately created them in His own image and likeness. The second chapter of Genesis contains an alternative creation account in which the order of the appearance of life forms on earth is somewhat reversed-but with a similar emphasis on the special creation of humans by God. Indeed, it is this second account that first introduces Adam and Eve as the progenitors of the human race, with God directly forming them as man and woman. The Bible does not state when these creation events occurred, but most early Christians probably assumed they all happened within the past six thousand years. During the mid-1600s, Anglican archbishop James Ussher of Dublin used internal evidence within the Bible to calculate the year of creation as 4004 b.c., or less than three thousand years before Genesis was supposedly written by the Hebrew leader Moses. Printed in the margins of the Authorized, or King James, version of the Bible, Ussher's chronology became quasi gospel for British and American Protestants during the eighteenth and nineteenth centuries.

Generally speaking, Christian leaders from the early church through the Reformation did not view the Bible as a scientific text. They interpreted it as a divinely authored or inspired volume of separately written books and letters filled with spiritual meanings, some of them allegorical. Science, in the sense of a distinct intellectual tradition seeking rational explanations for physical phenomena, began with ancient Greek natural philosophy roughly five hundred years before Christ. Although most individual Greeks probably accepted religious or mythical explanations for natural phenomena, some Greek philosophers sought to separate the supernatural from the natural by proposing purely materialistic accounts of nature. Nothing is aught but physical matter in meaningless motion, the ancient Greek atomists proclaimed. The origin of life and individual species posed a particular problem for Greeks intent on devising purely materialistic explanations for natural phenomena. Creation implies a creator, and so to dispense with the need for a biological creator, such ancient philosophers as Anaximander, Empedocles, the atomists, and the Epicureans advanced various crude notions of organic evolution.

Based on his close study of animal anatomy, however, Aristotle concluded that species are absolutely immutable. Each species always breeds true to its form, he maintained, and never gives birth to a new type. Rejecting both creation and evolution, Aristotle (an atheist) simply posited that species are eternal. Integrating the Genesis account with mainstream Aristotelean science, premodern Christian naturalists viewed species as created by God in the beginning and thereafter fixed for all time in a perfect (albeit fallen) creation. Well into the nineteenth century even Cuvier saw no scientific reason to reject Aristotelean thinking on the fixity of species-and fully appreciated the religious advantages of retaining it. Whether read literally or allegorically, the Genesis account harmonizes with the idea that species, once created, never change.

By 1800, Cuvier also had compelling social reasons for maintaining the traditional Aristotelean view of species. The breakdown of established authority associated with the Enlightenment in eighteenth-century France coincided with a revival of pre-Christian speculation about organic evolution and biological reductionism or materialism. At its core, the Enlightenment (the intellectual launching pad of modernity) involved a rational critique of previously accepted doctrines and institutions. To the extent that Christianity was based on divine revelation rather than human reason, it lost credibility among enlightened thinkers. Similarly, to the extent that they lacked rational justification, political and cultural institutions trembled or fell-including the ancien régime. During the 1790s in France, King Louis XVI lost his head and the Roman Catholic church was outlawed. Revolutionary currents swirled though natural history, as well. Some radical naturalist and

savants challenged static concepts in science, including the fixity of species; many of them rejected any ongoing role for the supernatural in the natural. Rational materialism gained ground in scientific, social, and political thought-with no clear separation among these disciplines. Disorder became the order of the day, and a reaction became inevitable.

Among eighteenth-century French scientists, Georges Louis Leclerc, comte de Buffon, personified the Enlightenment. One of the foremost descriptive naturalists of his day, Buffon was also a highly original theorist who, as superintendent from 1739 to 1788 of the Royal Garden (which became the Museum of Natural History after the Revolution), commanded the position and prestige to promote his novel ideas about nature. In all these respects-academic field, official status, and scientific renown-Buffon was Cuvier's predecessor but never his precursor. Although historians still debate whether Buffon was an outright atheist or simply a radical deist, he certainly rejected Christianity and sought materialistic explanations for the origin of the earth and its inhabitants. This led him to evolutionary thought.

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