It was only around 1800 that heredity began to enter debates among physicians, breeders, and naturalists. Soon thereafter it evolved into one of the most fundamental concepts of biology. Here Staffan Müller-Wille and Hans-Jörg Rheinberger offer a succinct cultural history of the scientific concept of heredity. They outline the dramatic changes the idea has undergone since the early modern period and describe the political and technological developments that brought about these changes.
Müller-Wille and Rheinberger begin with an account of premodern theories of generation, showing that these were concerned with the procreation of individuals rather than with hereditary transmission. The authors reveal that when hereditarian thinking first emerged, it did so in a variety of cultural domains, such as politics and law, medicine, natural history, breeding, and anthropology. Müller-Wille and Rheinberger then track theories of heredity from the late nineteenth century—when leading biologists considered it in light of growing societal concerns with race and eugenics—through the rise of classical and molecular genetics in the twentieth century, to today, as researchers apply sophisticated information technologies to understand heredity. What readers come to see from this exquisite history is why it took such a long time for heredity to become a prominent concept in the life sciences and why it gained such overwhelming importance in those sciences and the broader culture over the last two centuries.
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About the Author
Staffan Müller-Wille is a senior lecturer and research associate with the ESRC Centre for Genomics in Society and the Centre for Medical History, both at the University of Exeter. Hans-Jörg Rheinberger is director at the Max Planck Institute for the History of Science in Berlin. They are the editors of Heredity Produced: At the Crossroads of Biology, Politics, and Culture, 15001870.
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A Cultural History of Heredity
By Staffan Müller-Wille, Hans-Jörg Rheinberger
The University of Chicago PressCopyright © 2012 The University of Chicago
All rights reserved.
Heredity: Knowledge and Power
Genealogy is the oldest kind of logic. Humans have always made use of kinship and descent in mythology, in philosophy, and in the sciences to describe the constitution of the world. Key concepts of ancient logic such as genus and species possess genealogical connotations, and the relationships among these concepts were modeled on relations of parentage. According to Porphyry's Isagoge, an introduction to Aristotle's Categories from late antiquity, a species relates to its genus in the same way "as Agamemnon is an Atreid [i.e., one of the sons of Atreus] and a Pelopid and a Tantalid and, finally, of Zeus." Lines of descent reflect a degree of continuity, so that something can be learned about the properties of a present-day individual by following the chain of his or her ancestors. Descent forms a common fate, which acts sometimes like a blessing and sometimes like a curse under which—as the philosopher of religion Klaus Heinrich put it—"nobody can but repeat the configurations (because they give him substance) that already were the configurations of the actions of his parents."
This way of thinking—this "mental disposition toward origin myths" (ursprungsmythische Geisteslage), as Heinrich characterized it—is alive and well today. In 2002, the publishing house of the Swedish daily newspaper Dagens Nyheter issued a biography of Karl Vilhelm Ossian Dahlgren, professor of botany at the University of Uppsala in the 1920s and 1930s. Dahlgren was a prominent supporter of eugenic and race-biological policies. He even directed his convictions against his own children, who took after his small and black-haired wife. In all seriousness, he advised them to refrain from having children. His advice was obviously ignored, for it was his own granddaughter, the journalist Eva F. Dahlgren, who became his biographer. About the reasons that motivated her to tell the story of his life, she said in an interview that the thought of her grandfather having been a race biologist had caused her to feel ashamed, even if she did not share his convictions. Yet she added, "I also have my grandfather's irregular teeth, and who knows what else went into the heritage?" Such a remark may appear anachronistic from a strictly genetic point of view, but in a certain sense Dahlgren is right. In her book, she recalls how much her grandfather impressed her when she was a child. To describe family influences as "heritage," and to allow for connotations that derive from modern genetics, is perfectly legitimate in everyday and literary contexts. Genetic images lend themselves to fabricating life histories of varying degrees of sophistication.
Faced with the ubiquity of such figures of thought, many will be surprised to learn that a strictly naturalistic concept of heredity—according to which that which is transmitted from generation to generation through the germ line counts as the "first," strictly biological, nature of a human being—is a relatively recent product of science. Until well into the nineteenth century, a medical tradition dating back to antiquity recognized six "non-natural things" (res non naturales) as well as seven "natural things" (res naturales) that together determined the constitution and character of individuals. The non-natural things included things that could be influenced, like nutrition, environment, rest, exercise, bodily excretions and psychological states, whereas the natural things encompassed components of the body (like spirits, elements, humours, and organs) as well as aspects resulting from the overall organization of these components (like functions, capacities, and temperament). The "natural things," moreover, were not linked to a hereditary substance, but were rather thought to result from the direct, physical creation of the embryo by both parents, or as some believed, by one of its parents only. Until the end of the eighteenth century, naturalists and physicians did not talk about biological "inheritance," a substance transmitted independently from the processes and circumstances of conception and development. And it took until the middle of the nineteenth century for "heredity" in this sense to emerge as one of the central problems of biology, especially in the works of Charles Darwin and of his cousin Francis Galton. With genetics and molecular biology in the twentieth century, heredity became a clearly delineated phenomenon that lent itself to experimental and mathematical treatment. Its existence was now beyond dispute, even if questions remained about its underlying mechanisms and how these could be exploited technologically to further analyze the phenomena of heredity.
Relatively precise dates can thus be given for the historical origins of the concept of heredity. In addition, the concept went through an initial phase of thorough problematization, followed by a phase of solidification into a measurable and manipulable research object. The roots of the knowledge regime from which the concept of heredity emerged extend, as we will see, to the early modern period, and in some instances even back to the early fourteenth century. This was the period in which Europeans began to conquer the globe, discovering at the same time that they were not its sole inhabitants; the period in which Europeans realized that progress and innovation could lead to the destruction of traditions, institutions, and even of whole cultures; the period in which Europeans gradually came to the conclusion not only that nature determines history, but also that nature itself has a history. As a consequence, it appeared possible to make history by dominating nature. These conclusions were reached in the course of interactions with other peoples and natural environments, in the context of a movement that was not simply an expansion into empty space, but which presupposed and initiated massive translocations and transplantations, both of humans and of the plants and animals they cultivated. The knowledge regime of heredity—this is the central thesis of our book—started to unfold as people, goods, and the relationships they mediated began to move and change on a global scale.
Thinking about heredity as originating from a knowledge regime that was oriented toward the mobilization, rather than the fixation, of the conditions of life has two implications. First, we cannot assume that heredity was a concept that had a definite meaning from the beginning. We are all familiar with ideas of inheritance or heritage that, above all, aim to capture a persistence of forms over time and are often employed to justify political authority and cultural traditions. In this sense, heritage becomes something worth upholding for its own sake. Ideological reifications of this kind are, of course, questionable. But in scrutinizing them, one should not overlook the fact that the political dimensions of concepts of heredity can be and have been the result of very different classificatory and causal assumptions and that such concepts were used for widely different ideological purposes. For example, itmakes a difference whether the inheritance of individual properties and the inheritance of species-typical properties are thought of as distinct processes or whether both are analyzed in a common framework. It similarly matters whether heredity is considered to be a reversible process to some degree or whether it is thought of as an irreversible series of distinct events. We will see that opinions with respect to these questions varied widely over time. The contours of consensus and of a scientific discipline of heredity emerged only gradually with certain conceptual and methodological suppositions, and have never been beyond contestation, as we experience now in the so-called postgenomic era.
Second, our approach implies that these variations and changes in thinking about heredity are best understood in the context of the institutions and discursive practices that constituted the knowledge regime of heredity. The distinction that eighteenth-century naturalists began to draw between "constant" characters and characters that vary with climate and other environmental conditions, for example, was connected with attempts to acclimatize exotic plants and animals to the temperate regions of Europe. When naturalists sought to distinguish between these types of characters, especially in institutions such as botanical gardens, they soon discovered "constant varieties"; that is, varieties that always transmitted their often trifling differences, even under changing environmental conditions. In the history of investigations into hereditary phenomena, we encounter this kind of development repeatedly. Typically, when a generally accepted dichotomy such as constant versus varying character was subject to scrutiny, phenomena that called for alternative descriptions and explanations were brought to the fore. Once the taxonomies and causalities subsumed under the concept of heredity were put into practice and institutionalized, they furnished the very conditions for the recognition of evidence to the contrary, which in turn called for the resolution of ensuing conceptual challenges.
Before we begin to unravel this complicated history, we would like to expand these two points to sketch out our view of heredity for the benefit of the reader. The work of Francis Galton—whom some historians consider the modern founder of research into heredity—provides a suitable starting point. Galton was indeed one of the first biologists who placed heredity at the center of their theorizing, and he employed a particularly rich arsenal of analogies and figures of thought in his attempts to make sense of heredity. As we will see in the following pages, some of these analogies and figures of thought are well suited for describing the dynamic character of the knowledge regime of heredity.
Galton's Post Office: Heredity as an Epistemic Space
When we mentioned earlier that people did not speak about "heredity" in a biological sense until the end of the eighteenth century, we were in the first place making an observation about the use of language. Phenomena that we would nowadays explain in terms of heredity as a matter of course—for example, the fact that certain physical or psychological peculiarities run in families, or the curious phenomenon that children sometimes show similarities to their grandparents rather than their parents—were already recognized in antiquity. The now dominant biological sense of the term "heredity," however, resulted from a metaphorical transfer of a juridical concept to a description of the generation and propagation of living beings. Generally speaking, such a transfer simply did not take place before the eighteenth century. Such historical facts about terminological use evoke the curiosity of historians of science. After all, analogies between juridical and biological inheritance seem to offer themselves quite readily. The inheritance of property is often connected to kinship, and thus—from today's perspective at least—to a biological relationship. Why then should people not have talked about the transmission of physical traits in terms of "inheritance" in the past?
In the original juridical sense, heredity, just like inheritance, refers to the distribution of status, property, and other goods in temporal succession and according to a system of rules and distinctions that regulate how these goods are passed on to other persons upon the death of a proprietor. The distinctions usually discriminate between groups of various degrees of kinship, and the rules determine under which conditions these groups can claim a certain portion of the inheritance. Thus in many regions of early modern Europe, inheritance rules were laid down according to which property would always be passed on to the first born—an institution known as major at or primogeniture. Today many countries possess laws that guarantee at least a portion of an inheritance to all close kin, independently of gender or birth order. The historical and cultural diversity of such regulations is enormous. The rather trivial but essential point we want to make here is that they always involve classifications of kin and rules of distribution.
This basic consideration already puts us in a position to identify an important precondition that had to be met before a transfer of ideas of inheritance from the sphere of law to that of biological reproduction could take place. The reproduction of organisms first had to appear as a process in which something was transmitted and redistributed in a regular fashion. And it is precisely this perspective that is missing in the works of great premodern and early modern natural philosophers such as Aristotle, William Harvey, or René Descartes. As we will see in the next chapter, their observations and speculations focused instead on the procreative act of generating an individual. To mark out the contours of a system to which the metaphor of inheritance, so rich in connotations, could be applied in a productive and useful way, one had to go beyond this point of view; it was necessary to establish connections between individual acts of procreation. Understanding propagation as a kind of inheritance, we can already say at this point, presupposed an identification of factors at work in propagation that persisted beyond the transitory moment of creating an individual being.
Francis Galton made this point repeatedly in his 1876 essay "A Theory of Heredity." Heredity, he claimed, could be explained only if one presupposed an organic system that endured across, and thus supported, successive generations. Galton called this system the stirp (from the Latin stirps, "descendant" or "stock," also used in the sense of "family branch," "son," and "heir"). According to Galton, the stirp was "the sum-total of the germs, gemmules, or whatever they may be called, which are to be found, according to every theory of organic units, in the newly fertilised ovum." To illustrate the structure of the stirp, Galton resorted to analogies that appear curious, even awkward. Among other things, he compared heredity to a post office:
Ova and their contents are, to biologists looking at them through microscopes, much what mail-bags and the heaps of letters poured out of them are to those who gaze through the glass windows of a post office. Such persons may draw various valuable conclusions as to the postal communications generally, but they cannot read a single word of what the letters contain. All that we may learn concerning the constituents of the stirp must be through inference, and not by direct observation; we are therefore forced to theorise.
Galton stressed that such comparisons were not meant to be "idle metaphors, but strict analogies," analogies worth "being pursued, as they give a much-needed clearness to views on heredity." A closer look at his comparison to a post office reveals what Galton had in mind when he called for concrete models of heredity. The comparison operates on two levels. On a first level, by referring to a communication technology that was developing rapidly at the time, Galton described heredity as a complex arrangement of spatial elements. The mail bags stand for the cytological space of the fertilized egg, "a space not exceeding the size of the head of a pin"; the letters for the elements of the stirp, the "germs and gemmules" that fill this cytological space but at the same time inhabit the much wider space of "postal communications" among ancestors and descendants. Put differently, heredity is defined by a structure, the stirp, that comprises both genealogical and cytological relationships inasmuch as the former must somehow be represented in the latter. Galton expressed this idea in the following terms: "everything that reached [a person] from his ancestors must have been packed in his own stirp."
On a second level, Galton's comparison to a post office illustrates how heredity becomes a subject for scientific research. The post office building, with its windows, represents the various tools and technologies that scientists employ to make sense of the phenomena of heredity. Microscopes alone, as Galton admitted, were certainly not enough. The description of heredity as a complex system of postal communications observed through the windows of a post office suggests that an equally complex configuration of technologies needs to be in place before one can discern the contours of heredity. To mention only the most obvious of these technologies, reliable means for recording genealogical data are necessary to observe the genealogical dimension of heredity. The comparison of this assemblage of technologies to a post office is significant in two further respects. First, it contains heredity within its own phenomenal space, separating it from other biological phenomena such as development or nutrition. Second, it makes the relationships among the elements of heredity observable rather than demanding direct characterization of these elements themselves. Owing to the low resolution power of the instruments at his disposal, the observer may not be able to read the "letters," but he or she still remains in a position to say something about "postal communications in general."
Excerpted from A Cultural History of Heredity by Staffan Müller-Wille, Hans-Jörg Rheinberger. Copyright © 2012 The University of Chicago. Excerpted by permission of The University of Chicago Press.
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Table of Contents
Chapter 1: Heredity: Knowledge and Power
Chapter 2: Generation, Reproduction, Evolution
Chapter 3: Heredity in Separate Domains
Chapter 4: First Syntheses
Chapter 5: Heredity, Race, and Eugenics
Chapter 6: Disciplining Heredity
Chapter 7: Heredity and Molecular Biology
Chapter 8: Gene Technology, Genomics, Postgenomics: Attempt at an Outlook