Theological objections to The Origin of Species had also gained steam. “There is no country in the whole world in which the Christian religion retains a greater influence over the souls of men than in America,” Alexis de Tocqueville had famously observed, a century before; and in America, the challenge to Darwin took the form of dogged loyalty to the literal truth of the Genesis account. The Butler Act, signed into Tennessee law in 1925, banned the teaching of natural selection in place of special creation, and the Scopes trial upheld the act’s legality.2
But natural selection was also coming under heavy fire from biologists who were less concerned with its implications for morality and more puzzled by its ramifications for evolution.
Natural selection, working through chance variations, did nothing more than weed out the weak; this seemed to be a completely inadequate explanation for the progression, the increased complexity, the direction that seemed part of the history of life. Natural selection seemed far more likely to produce haphazard and unguided change. And so scores of prominent biologists (the Russian Lev Berg, the Austrian Ludwig von Bertalanffy, the German Otto Schindewolf, and many, many others) suggested various kinds of orthogenesis, the assurance that some predetermined pattern, or goal, or intention, lay behind the origin of species.
Better instruments, more data, and improved research techniques were yielding discoveries thick and fast, many of them (in cytology, biometry, embryology, genetics) suggesting that natural selection was indeed an adequate explanation for organic life. But these studies were clogged with technical language, inaccessible to the nonspecialist. There was, in Ernst Mayr’s words, “an extraordinary communication gap between the various disciplines of biology,” and an even greater gap between biology and the other sciences. Genetics, in particular, was yielding insight after insight, but geneticists were taking no time to build bridges from their discoveries to the phenomena that fieldwork in natural history had revealed: animal behavior, fossilized remains, the complex interactions of living environments.3
“Darwin’s selection theory . . . is far from explaining the ultimate causes of numerous adaptations,” noted Lehrbuch der Zoologie, a standard university text in Germany in the 1920s. Prominent botanist Wilhelm Johannsen was even more emphatic: “[It is] completely evident that genetics has deprived the Darwinian theory of selection entirely of its foundation,” he wrote. “We have never been less sure about the mechanisms of evolution,” admitted the French biologist Jean Rostand. And in 1937, Paul Lemoine, director of the National Museum of Natural History in Paris, went even further: “Natural selection plays no role,” he concluded. “The data of genetics furnish no argument in favor of evolution. . . . The theory of evolution will very soon be abandoned.”4
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Julian Huxley seems to have been genetically predestined to rescue Darwin.
His grandfather, Thomas H. Huxley, had been one of the earliest reviewers of the Origin of Species and afterward became one of Darwin’s most ardent supporters and friends. “The Origin of Species,” he had written to a friend, a dozen years after the book first appeared, “has worked as complete a revolution in biological science as the Principia did in astronomy.” All his life, T. H. Huxley remained such a fierce defender of Darwinian theory against its critics that he once nicknamed himself “Darwin’s bulldog.”5
Young Julian, born in 1887, was a naturalist from childhood: interested in “plants and animals, fossils and geography,” a frog collector, butterfly classifier, and bird-watcher. “Julian evidently inclines to biology,” his distinguished grandfather remarked when the boy was only four years old. “How I should like to train him!” He studied zoology at Oxford and, after his graduation in 1909, remained at the university to conduct experiments in a startling range of topics: embryology, ontogeny, cellular differentiation, morphogenesis, genetics, and (he always combined his laboratory work with field observations) the courtship rituals of redshanks and crested grebes.6
Julian Huxley remained in the academic world until the late 1920s: an effective and much-respected teacher and researcher, but restless, increasingly weary of undergraduates, unhappily married, and struggling with bouts of depression and mania. In 1926 the writer H. G. Wells invited him to collaborate on a massive encyclopedia of biology, intended to sum up the entire progress of the field. Wells, twenty years Julian’s senior, had studied biology in London under T. H. Huxley himself; he was already famous as the author of The Time Machine and The War of the Worlds (and many other books).
Julian seized at the opportunity, left his teaching post, and began work. He was a polished writer, but Wells (notoriously demanding and difficult) insisted that he refine his style even further, so that the increasingly complicated developments in biology would be accessible to lay readers. “I had learnt a great deal . . . under H. G.’s stern guidance,” Huxley later remarked, “about the popularization of difficult ideas and recondite facts . . . [and about] synthesizing a multitude of facts into a manageable whole, aware of the trees, yet seeing the pattern of the forest. . . . This, I may add, did not come easily.”7
The Science of Life was an international best seller, but the ability to write well on a very big subject turned out to be even more valuable than the royalties.
An increasing cadre of distinguished scientists—Julian Huxley among them—had begun to recognize the need to draw together new discoveries in genetics and other aspects of natural history into a whole: a Big Story, an explanation of how it all fit together. What was needed was a defense of Darwin that nevertheless took into account the need to bring Darwin’s original theory, now well over a half century old, into line with the newest discoveries in genetics and cytology. Both scientists and the public needed a greater understanding of “evolution at work,” the ways in which the grand theory and specific discoveries acted together.8
So, in the tradition of his grandfather, Darwin’s bulldog, Julian Huxley proposed in 1936 that a new society be founded: the Association for the Study of Systematics in Relation to General Biology. He was its first chair; and at its first meeting, on a Friday in June of 1937, seventy-four biologists attended. Among the goals of the new society, reported the journal Nature, was to “stimulate discussion and to promote cooperation between workers in different branches of biology.”9
The Russian entomologist Theodosius Dobzhansky, a regular correspondent of Huxley’s, and a fellow systematist, was already set to publish. Genetics and the Origin of Species (1937) brought together Dobzhansky’s laboratory work in genetics, his observations in the field (he had worked extensively with fruit flies), and the somewhat obscure (to nonspecialists) mathematical calculations of population genetics—all in order to argue that Darwinian natural selection did, indeed, account for the existence of species. It was one of the first systematic, big-picture works in modern biology, but far from the last.10
In the next decade, George Gaylord Simpson’s Tempo and Mode in Evolution, Bernhard Rensch’s Evolution above the Species Level, and Ernst Mayr’s Systematics and the Origin of Species, from the Viewpoint of a Zoologist all appeared. And Huxley was hard at work on his own big-picture volume. His Evolution: The Modern Synthesis appeared in 1942, and two things set it apart: Huxley was, intentionally, writing for the informed and interested layperson, not simply for his scientific colleagues; and Huxley, for the first time, had used the word synthesis.
“The death of Darwinism has been proclaimed not only from the pulpit, but from the biological laboratory,” Huxley begins, “but, as in the case of Mark Twain, the reports seem to have been greatly exaggerated, since to-day Darwinism is very much alive.” And his first chapter lays out his intentions:
Biology in the last twenty years, after a period in which new disciplines were taken up in turn and worked out in comparative isolation, has become a more unified science. It has embarked upon a period of synthesis, until to-day it no longer presents the spectacle of a number of semi-independent and largely contradictory sub-sciences, but is coming to riv
al the unity of older sciences like physics, in which advance in any one branch leads almost at once to advance in all other fields, and theory and experiment march hand-in-hand. As one chief result, there has been a rebirth of Darwinism. . . . The Darwinism thus reborn is a modified Darwinism, since it must operate with facts unknown to Darwin; but it is still Darwinism in the sense that it aims at giving a naturalistic interpretation of evolution. . . . It is with this reborn Darwinism, this mutated phoenix risen from the ashes of the pyre . . . that I propose to deal in succeeding chapters.11
It was a sprawling, multifaceted task, and Evolution: The Modern Synthesis is a sprawling, multifaceted book, covering in turn paleontology, genetics, geographic differentiation, ecology, taxonomy, adaptation, and the idea of evolutionary progress.
But Huxley’s training period with H. G. Wells had served him well. The clarity of his style and the down-to-earth, jargon-free presentation of technical ideas made Evolution both readable and an instant success. “The outstanding evolutionary treatise of the decade, perhaps of the century,” exclaimed the American Naturalist, one of the most important journals of the field, and readers agreed. Huxley’s book went through five printings and three editions; the latest, in 1973, included a new introduction, coauthored by nine prominent scientists, affirming the overall truth of the synthesis and updating its data.12
From 1942 on into the twenty-first century, this entire endeavor—the careful connection of cell-level studies in genetics with the larger world of natural history—would continue, drawing from a wider and wider array of developing subspecialties (such as the late-twentieth-century field of evolutionary genomics). And it would continue to take its name from Huxley’s book: the modern synthesis. Huxley had resurrected Darwin, and the “mutated phoenix” was evolving steadily forward.
JULIAN HUXLEY
Evolution: The Modern Synthesis
(1942)
In 2010, MIT Press published the 1942 text of Evolution: The Modern Synthesis along with Huxley’s original preface, as well as the introductions to the second and third editions.
Julian Huxley, Evolution: The Modern Synthesis: The Definitive Edition, MIT Press (paperback, 2010, ISBN 978-0262513661).
TWENTY-THREE
The Secret of Life
Biochemistry tackles the mystery of inheritance
Science seldom proceeds in the straightforward logical
manner imagined by outsiders.
—James D. Watson, The Double Helix, 1968
For a hundred years—at least since Lamarck—the science of life had accepted that living creatures pass attributes to their young. But how this worked was a mystery. Something was inherited; but what? What did it look like; how did it behave; where was it? And how did this “pangene,” this unit of information, go about producing a similar eye color, or height, or fur pattern, in the next generation?
In 1953 the young American James Watson and his British colleague Francis Crick, working in Cambridge, discovered the answer: DNA, the double-helix strands of molecules that replicate a parent’s characteristics in a child. Crick was so thrilled that he bounded into the nearest pub and announced to all within earshot that he had just found “the secret of life.” This, as scores of science texts will tell you, was a discovery that “changed the world”; “one of the most important scientific discoveries of the twentieth century”; “the birthday of modern biology.” Fifteen years later, James Watson guaranteed the immortality of that watershed moment by writing an instantly popular account of his work on DNA: The Double Helix.1
But the existence of deoxyribonucleic acid had been known for over a century. And its double-helix structure would not actually be observed for years to come. The “discovery of DNA” was, in fact, a series of minute advances forward in chemistry, biology, and even physics, rooted in seventeenth-century technology, carried out over the decades that bridged the nineteenth and twentieth centuries, dependent on the work of scores of scientists, and finally channeled by one charismatic researcher into a best-selling popular account.
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Since Robert Hooke first peered through his microscope at a piece of cork, natural scientists had accepted that living things were made up of separate bits, like a whole honeycomb divided into tiny parcels of sweetness. “The substance of Cork is altogether fill’d with Air,” Hooke had written, in Micrographia, “and . . . that Air is perfectly enclosed in little Boxes or Cells, distinct from one another.” Hooke observed cells in many living things, as far distant as petrified wood and spiders; following his lead, other observers discovered cells in all sorts of vegetables, in embryos, in animal tissues.
What was inside those cells, and why they existed at all (why not simple undifferentiated flesh?), defied eighteenth-century science. But by the late 1830s, making use of improved instruments to extend their senses, two different observers (the French biologist Félix Dujardin, and Jan Purkinje of Bohemia) concluded that Hooke’s tiny boxes were filled with a “glutinous, diaphanous substance,” sticky and intractable, essential to life: protoplasm, as Purkinje called it. Protoplasm was the most basic “material of life,” a fundamental jelly whose exact purpose was still unknown.2
In 1847, two German naturalists—botanist Matthias Jakob Schleiden and zoologist Theodor Schwann—defined Hooke’s cells as the first and most fundamental unit of life. In each new living thing, cells grew and developed, starting as tiny grains and expanding outward: “It is an altogether absolute law,” Schwann wrote, “that every cell . . . must make its first appearance in the form of a very minute vesicle, and gradually expand to the size which it presents in the fully-developed condition.” This cell, confirmed the German biologist Max Schultz in an 1861 paper, was a ball of protoplasm containing a distinct center—a nucleus (from the Latin word for “kernel” or “nut”).3
Meanwhile, chemistry—a field that had been preoccupied with metals, gases, and other inorganic substances ever since Robert Boyle’s seventeenth-century elaborations—had been set on an intersecting course with biology. In 1828 the chemist Friedrich Wöhler accidentally produced the organic compound urea, naturally found in urine, in his lab. (“I can make urea without needing a kidney!” he wrote to a colleague in great excitement.) The unexpected synthesis suggested that organic substances could be understood through the same basic chemical laws that were known to govern inorganics. Cells could be prodded, stimulated, catalyzed, broken apart, subjected to chemical tests, understood by means of their chemical reactions: the beginnings of biochemistry.4
The infant science grew quickly. In 1833, the French chemists Anselme Payen and Jean-François Persoz discovered that something in malt (they called it “diastase”) had the ability to change starches into sugars. Diastase was the first known enzyme—an organic molecule, generally a protein, that sets a chemical reaction into motion and has the potential to change a living thing. Four years later, the Swedish chemist Jöns Berzelius came up with the name catalysis, a process “different from [those] previously known to us,” which has the power to cause “a rearrangement of the constituents of the body into other relationships.” The discovery of catalysis had implications far past the test tube. When, Berzelius wrote,
we turn with this idea to living Nature, an entirely new light dawns for us. It gives us good cause to suppose that in living plants and animals thousands of catalytic processes are taking place between the tissues and the fluids, producing the multitude of dissimilar chemical compounds for whose formation from the common raw material, sap or blood, we had not been able to think of any cause, but which in the future we shall probably find in the catalytic power of the organic tissue.5
The ultimate explanations for our biological existence, for our shape and form, lay in chemistry—in understanding the reactions that gave rise to our cells and governed their interactions.
But the cell was still an uncharted territory, and neither biologists nor chemists could do much more than guess at its contours.
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In
1865 the Swiss medical student Friedrich Miescher recovered from typhoid fever, but not without scars: his hearing had been damaged, one ear left completely deaf.
This made patient care difficult, so Miescher decided to occupy himself with medical research instead. He took his lead from an uncle, the distinguished physician Wilhelm His: “I came to the conclusion,” His later wrote, in his personal papers, “that the final solution of the problems of tissue development could be solved only by chemistry.” Miescher’s own chemical interests lay in the exact makeup of the cell—particularly the mysterious nucleus, difficult to glimpse, its function unknown. He had noticed that the nuclei of lymphoid (white blood) cells were, observably, larger in proportion than those of other cells, so he decided to collect pus from discarded surgical bandages, isolate the nuclei of the white blood cells (using various solvents, as was the accepted practice), and analyze their makeup.6
Miescher’s experiments, conducted over a two-year period and published in 1871, revealed an unexpected presence. It was generally believed that nuclei contained proteins, considered to be (in some way) the building blocks of life. But these nuclei broke down into two different parts—a protein, yes, but also a previously unknown, lightly acidic substance. Miescher gave this new acid a name: nuclein.*
In 1929 the Lithuanian biochemist Phoebus Levene, driven to the United States by anti-Semitism in his own country and now working at the Rockefeller Institute in New York, identified one of the most abundant elements in Miescher’s nuclein as containing a sugar called deoxyribose. He called this particular acid in the nuclein deoxyribonucleic acid.7
Miescher had discovered DNA; Levene had named it. Neither man had any idea what it did.
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The Story of Western Science Page 19
