In the mid-twentieth century, American plant breeders, frustrated by their dependence on natural variation in creating new crops and flowers, eagerly sought technologies that could extend human control over nature. Their search led them to celebrate a series of strange tools: an x-ray beam directed at dormant seeds, a drop of chromosome-altering colchicine on a flower bud, and a piece of radioactive cobalt in a field of growing crops. According to scientific and popular reports of the time, these mutation-inducing methods would generate variation on demand, in turn allowing breeders to genetically engineer crops and flowers to order. Creating a new crop or flower would soon be as straightforward as innovating any other modern industrial product. In Evolution Made to Order, Helen Anne Curry traces the history of America’s pursuit of tools that could speed up evolution. It is an immersive journey through the scientific and social worlds of midcentury genetics and plant breeding and a compelling exploration of American cultures of innovation. As Curry reveals, the creation of genetic technologies was deeply entangled with other areas of technological innovationfrom electromechanical to chemical to nuclear. An important study of biological research and innovation in America, Evolution Made to Order provides vital historical context for current worldwide ethical and policy debates over genetic engineering.
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About the Author
Helen Anne Curry is the Peter Lipton Lecturer in History of Modern Science and Technology at the University of Cambridge.
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Evolution Made to Order
Plant Breeding and Technological Innovation in Twentieth-Century America
By Helen Anne Curry
The University of Chicago PressCopyright © 2016 The University of Chicago
All rights reserved.
In all likelihood, the first person to voice a desire to control "mutation" in order to improve plant breeding, and to suggest radiation as a means of achieving this, was the very man who introduced the concept of mutation into biological theory: the Dutch botanist Hugo de Vries. In the summer of 1904, de Vries presented his ideas to an audience that had gathered in Cold Spring Harbor, New York, to celebrate the opening of the Carnegie Institution of Washington's Station for Experimental Evolution. By that time, de Vries was internationally known for his mutation theory in which he had proposed a new explanation of evolutionary change. He was enthusiastic about the research station at Cold Spring Harbor and the studies that were to be carried out there, believing it was crucial that researchers consider evolution using new approaches and new ideas. "We want to share in the work of evolution, since we partake of the fruit," de Vries explained, speaking of the mission of experimental evolutionists. "We want even to shape the work, in order to get still better fruits."
To de Vries, the trajectory that experimental research on evolution should follow was clear. First, scientists would elucidate the nature of mutation, the basis of evolution, by working with species found to be changing in nature. Then they would seek the causes of these mutations. The culmination of the field would be the application of this knowledge to produce mutations — and therefore evolution — on demand: "New and unexpected species will then arise, and methods will be discovered which might be applied to garden plants and vegetables, and perhaps even to agricultural crops, in order to induce them to yield still more useful novelties." De Vries thought that the radiations generated by the curious phenomenon of x-rays and the recently discovered element radium might prove key to the final part of this research program in which scientists would generate mutations at will.
When de Vries referred to "mutations," he did not have in mind the biological events this term would later be used to describe. In his mutation theory, first published in 1900, he used the word to indicate the striking changes in inherited traits he observed among his experimental flowers, changes that he believed set one species apart from another in a single generation. He considered these leaps in form to be a more important component of evolutionary change than the Darwinian process of gradual differentiation via natural selection. De Vries's theory rose quickly to prominence, inspiring all kinds of research into mutation. Although it fell out of favor almost as fast as it had risen, the notion of mutation found a lasting place in biological theory. What's more, many biologists in subsequent decades would share de Vries's vision of evolution as a process that could potentially be directed by human beings through their control of mutation.
Before turning to that history, it is essential to place de Vries's ideas about the study of evolution and heredity in a broader social and intellectual context. His emphasis on the literal fruits of research in his 1904 address, for example, is a reminder of the immense importance attached to the potential practical payoffs of the study of heredity and evolution at the turn of the century. This point will be obvious to readers who know the story of the so-called rediscovery of Gregor Mendel and the subsequent reception of his studies of inheritance in sweet peas: Beginning in 1856, Mendel, an Augustinian friar in Brno, Moravia (then part of the Austrian Empire), hybridized plants and tracked the inheritance of specific traits from generation to generation. In 1865, he reported his results to his local natural history society. He described how the visible characteristics of his pea plants — such as their height, the color and texture of their seeds — were determined by discrete hereditary elements within their cells. Mendel's observations and statistical analyses of the patterns of inheritance enabled him to propose a set of rules that governed the behavior of the hereditary elements, later called Mendelian factors or unit characters, and therefore the appearance of the traits they determined. These rules in turn could be used to predict the distribution of traits among the offspring of a given hybrid combination of pea plants. This work drew scant attention until a few scientists, de Vries included, came across it in the course of their own research around 1900. New generalizations about inheritance based on Mendel's ideas, generalizations that we know today as the laws of segregation and independent assortment and the concept of dominant traits, soon circulated widely, welcomed especially by many biologists, breeders, and eugenic advocates. It is not hard to see why. The laws seemed to offer both an explanation for patterns long observed by breeders and hybridizers — and therefore a validation of their methods — and a route to predicting and potentially controlling the inheritance of traits in plants, animals, and humans alike. Mendel's ideas found many champions, especially in the United States and Britain. Their "rediscovery" is generally credited with sparking the development of the field we know as genetics.
In the United States, the promise that heredity might be better understood and controlled meshed well with ambitions for a more scientific approach to agriculture. The scientific investigation of inheritance promised to be economically relevant, as research in the emergent discipline of genetics could easily be directed toward agricultural improvement. Studying patterns of inheritance in chickens, for example, might produce better egg layers as much as it might illuminate the underlying mechanisms through which traits are passed on from one generation to the next. And just as researchers pursuing studies of Mendelian inheritance sought to show how their knowledge might be applied in this way, breeders sought to demonstrate how the new genetic ideas aligned with their existing expertise and established methods. The upshot was an alliance between advocates of Mendelian genetics and agricultural breeders, one that helped ensure the success of Mendelism in the United States, in laboratory and farm fields alike.
From about 1900, then, the introduction of Mendelian genetics provided a conceptual and practical tool for American breeders to claim control over the direction of evolution in domesticated plants and animals. Yet Mendel's laws neither explained the origins of variation in heritable characters among individuals or types nor indicated how such variations might be produced — and variation was the crucial currency of both natural evolution and selective breeding. One could hardly imagine a new species or an improved breed coming into existence without some characteristics that set it apart from its progenitors. As a result, ideas beyond Mendelian genetics proved influential in spurring early research into the nature of heritable variation. Foremost among these ideas were de Vries's mutation theory of evolution, with its emphasis on understanding and perhaps controlling the appearance of novel types, and the work of his contemporary Luther Burbank, an American horticulturist, in creating new varieties of flowers, fruits, and vegetables. Each in its own way encouraged people to believe that the variations in heritable traits found among plants and animals might be generated on demand.
Hugo de Vries's botanical investigations began early. He had been an avid botanizer even from childhood, gathering specimens from the countryside near his family home in Haarlem, and his interest in the study of plants persisted into adulthood. After graduating from Leiden University, the young de Vries spent a few summers in the early 1870s studying plant physiology under the eminent German botanist Julius von Sachs before going on to establish an independent research career. While at university, de Vries had read Darwin's On the Origin of Species and had become something of a Darwin devotee, an interest that inspired his turn to the study of heredity and evolution in the late 1870s. Hoping to get a better grasp of these processes, de Vries carried out extensive plant hybridization experiments. It was this work that led him to the 1865 paper by Mendel on inheritance in sweet peas, and subsequently to its recirculation and then celebration.
Having been instrumental in calling attention to the theories of Mendel, de Vries followed up with a novel biological theory of his own. In Die Mutationstheorie, released in two volumes in 1901 and 1903, de Vries sought to revise one of the central tenets of Darwin's evolutionary theory, the notion that evolution and speciation occur through gradual change. Darwin's hypothesis was that natural selection acted on the small differences among individuals — so-called continuous variations in traits — to produce evolutionary change over many generations. De Vries disagreed. According to his mutation theory, new species were assumed to arise as a result of sudden and distinct changes in form, also called discontinuous variations or "saltations." Natural selection might then act on these saltations to weed out the less fit of any new "elementary species."
De Vries had arrived at this conclusion through his observations of the evening primrose, Oenothera lamarckiana. In 1886, he had encountered a population of these flowering plants growing in a field near Amsterdam and had been struck by the species' unusual displays of variability. Keen to observe the plants more closely, he transplanted several to his experimental garden and cultivated them over a few generations. The plants rewarded his curiosity. Instead of offspring looking for the most part like their parents, generation after generation, as one might expect, Oenothera plants were prone to producing offspring that differed in basic characteristics (fig. 2). De Vries introduced the term "mutation" to describe these deviations in form. He inferred from his observations that he was watching speciation in action: the differences from one generation to the next were, in his estimation, significant enough to mark the origin of an entirely new species of Oenothera. The further implication was that species might well arise from abrupt alterations in form, as opposed to small gradual changes accumulating over time as Darwin had proposed.
Although de Vries drew his strongest evidence from Oenothera, he also looked to the accumulated wisdom of horticulturalists, especially those working with flowers and fruits, to support his mutation theory of evolution. Horticulturists were familiar with the sudden occurrence of distinct and stable new forms, such as a white rose with an unusual flush of pink or a peach with smooth skin rather than fuzzy. These were referred to as "sports," and those that were particularly appealing could be propagated through grafting, cutting, or other means, and sold as novel varieties. To de Vries, "the so-called sports," these sudden leaps in form used to establish distinct lines, were the best-known examples of what he now categorized as mutations.
De Vries's mutation theory proved influential in the first decade of the twentieth century. Far more important than its challenge to Darwinian evolutionary theory, however, was its effect on methods of biological investigation, as de Vries's speculations spurred other scientists to study evolution via experiments. For example, Thomas Morgan, a professor of zoology at Columbia University in New York, began searching in 1907 for a way to study evolution experimentally just as de Vries had envisioned. Working with the common fruit fly, Drosophila melanogaster, Morgan initially sought to produce or discover a de Vriesian mutation. His efforts, slow to start, eventually led him to identify many distinctive and apparently new traits among his laboratory populations. This in turn led him into what would become an enormously productive and influential experimental program — though not in experimental evolution but in genetics. De Vries's theory was also of great interest to those engaged in plant breeding. Just as the theory sought to explain the origin of new species, so too did it shed light on the production of new cultivated varieties. As de Vries suggested, an appreciation of the "high practical value of the elementary species [those newly arisen via mutation] ... will, no doubt, soon change the whole aspect of agricultural plant breeding." Journalists proved particularly responsive to this facet of de Vries's work. Sensational news reports, inspired by lectures given by de Vries or his admirers and running under headlines like "How to Increase World's Foods" or "Grow Larger Grain," declared that mutation theory would soon lead to higher-yielding rice and wheat.
The application of mutation theory to breeding practices was hardly as direct as these reports, or de Vries himself, suggested. At the time, most agricultural breeders working with field crops grown from seed — oats, barley, corn, cotton, and others — worked to improve varieties through mass selection. Breeders would save the seeds from many of the "best" plants grown in a season, judging "best" by whatever criteria they thought most appropriate, and sow this mixed lot of seed the following year. The process was continuous. A breeder had to attend season after season to the most desirable traits or else the population would gradually return to its original form. How would mutation theory improve on this practice? For one, de Vries reasoned that breeders could be saved the trouble of selection, if only they could be taught to seek out plants bearing true mutations. These would not revert to ancestral characteristics if left to breed freely in the way that varieties maintained through selection of normal variations would. In other words, looking for desirable mutations and selecting these would make breeding far more efficient. But de Vries was not content to simply observe and utilize mutations where these had arisen through natural processes. He also hoped that the appearance of mutations might be controlled. "A knowledge of the laws of mutation must sooner or later lead to the possibility of inducing mutations at will and so of originating perfectly new characters in animals and plants," he speculated. This in turn would "place in our hands the power of originating permanently improved species." Once this power was achieved, breeders would be spared waiting and searching for spontaneous changes when seeking desired traits, just as they would be spared the task of continuous selection. In this vision, mutation theory, and mutation research, would revolutionize breeding practices.
To de Vries, the ability to direct mutation — and with it, evolution — was a thing of the future. But others at the time believed that skilled breeders already possessed this ability. Not long after the publication of his mutation theory, de Vries became embroiled in a high-profile dispute on exactly this point. At the center of the commotion was a famous California horticulturist named Luther Burbank. In the decade before the rediscovery of Mendel and de Vries's proposal of his mutation theory, Burbank had captured national and even international attention through his creation of impressive new varieties of flowers, crops, and especially fruits — and through his canny self-promotion. By the turn of the century, he was a much-loved public figure. Just as there was the "wizard of Menlo Park," the great inventor of mechanical devices Thomas Edison, there was a "wizard of Santa Rosa," the inventor of flowers and fruit trees Luther Burbank.
Early in his career, Burbank had garnered a reputation for creating striking improvements in fruit tree varieties. In one famous example of his efforts, Burbank in the late 1870s and 1880s developed several varieties of orchard plums. In order to introduce novel characteristics into the varieties already established in the United States, Burbank imported Japanese plum varieties, which he then hybridized with American and European ones. By 1887, he had forty-three hybrid varieties ready to share, many displaying new qualities derived from the Japanese plums, features like red flesh and earlier ripening. These proved to be an immediate success and counted among the most popular plant innovations he ever produced. The process by which Burbank had produced the plums was typical of his methods. He sought out desirable traits in specific plants or varieties and bred these with individuals from the stock he wanted to improve, selecting for the coveted traits in subsequent generations.
Excerpted from Evolution Made to Order by Helen Anne Curry. Copyright © 2016 The University of Chicago. Excerpted by permission of The University of Chicago Press.
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Table of Contents
List of Abbreviations Introduction Part 1 Evolution by X-ray: The Industrialization of Biological Innovation 1 Mutation Theories 2 An Unsolved Problem 3 Speeding Up Evolution 4 X-rays in the Lab and Field 5 Industrial Evolution Part 2 Tinkering with Chromosomes: Colchicine in the Lab and Garden 6 Artificial Tetraploidy 7 Evolution to Order 8 Better Evolution through Chemistry 9 Tinkering Technologists 10 The Flower Manufacturers Part 3 Atoms for Agriculture: Evolution in a Large Technological System 11 Radiation Revisited 12 Mutation Politics 13 An Atomic-Age Experiment Station 14 Atomic Gardens 15 The Peaceful Atom in Global Agriculture Epilogue Acknowledgments Notes Bibliography Index