Darwin Mendel and a New Theory of Variation

Plant breeding in general and wheat breeding specifically were rudimentary activities on many grounds in the nineteenth century. Not many people engaged in the activity. Those who did were self-taught, because no formal educational programs existed in the subject. For the most part, they had only a few very modest institutional bases within which to work. Many farmers paid them little or no attention, and governments usually ignored their contributions and gave them next to no support. They had no organized way of broadly disseminating their results, which in any case were few in number.

By 1970, wheat and other plant breeders occupied a very different position within both the scientific and political economic landscapes. Many people worked as breeders.1 They were highly trained in educational programs dedicated to the reproduction of plant breeders. Elaborate networks of institutions gave them employment. A substantial proportion of farmers cared very much what they did, and governments gave substantial, sometimes lavish, support. They had means of communicating their work that included both scientific and popular outlets. And they had substantial results to convey to farmers and the general public, some of them remarkable either for their scientific cleverness or for their broad political, economic, and ecological impacts, or both.

Another way of gaining perspective on the change in status of wheat and other plant breeders is to suggest that their absence might not have been noticed by any body but their families had they suddenly disappeared in the nineteenth century. In contrast, the twentieth century came increasingly to depend upon the plant breeders. Cessation of wheat breeding after 1970, for example, would have put some agricultural systems in distinct danger of slow decline or even collapse and failure. In both political economic and ecological terms, an increasing portion of the global human community became absolutely dependent upon wheat breeders and other plant scientists, certainly for prosperity as we now know it and possibly for survival and security.

The transformation of wheat breeding from nearly invisible to virtually indispensable resulted from two mutually interacting events: a commercial-industrial revolution in agriculture and construction of a new science of plant breeding. The new science had its origins in a philosophy of variation and inheritance grounded in the works of Charles Darwin and Gregor Mendel. Darwin's thoughts were widely discussed after 1859, and Mendel rose to scientific prominence after 1900. The two worked independently, and it was only after both had died that their ideas joined as the foundation of a new applied science of plant breeding. Events in England and the United States were paramount, but other major contributions came from Sweden, Denmark, Germany, and elsewhere.

Nineteenth-century wheat improvers found and created new varieties with higher yields, but until Darwin's work from 1859 to 1868, variation was generally understood as the result of divine creation or the result of slow change over time of one form into another.2 After Darwin, wheat breeders may still have been uncertain about the origins and heritability of variation, but they had an entirely new framework for seeing variation as the source of new varieties and new species of plants and animals. Darwin placed either natural selection or the actions of breeders and fanciers as the cause, over a period of time, of the production of new species or new varieties, respectively.

Darwin's provisional hypothesis of pangenesis was a valiant effort to account for how specific characteristics of a particular individual could be passed on to future generations in a way that allowed natural selection or selection of fanciers to create their new species or varieties. In pangenesis, each cell of an individual produced granules or gemmules that dispersed throughout the organism, multiplied by self-division when given proper nutriment, and ultimately produced new cells like the ones from which they were formed. The sexual elements were collections from all parts of the individual of all the different types of gemmules, and this collection gave rise to the next generation. Gemmules could also be dormant in a generation but still be passed on to subsequent generations, where they would develop.3

Pangenesis was a reasonable attempt by Darwin to account for a number of things he knew about inheritance and development, but for a variety of reasons it was found wanting and never attracted much support. Darwin himself seemed highly tentative about his proposal. Gregor Mendel, however, working somewhat before Darwin developed the idea of pangenesis, outlined a mechanism of inheritance that ultimately attracted support. It was Mendel's theory of the transmission of factors governing unit characters that ultimately found acceptance and elaboration among those scientists who worked to understand the origins, transmission, and significance of variation.

We will come shortly to the ways in which Darwin's and Mendel's theories entered the work of plant breeding, but it is first necessary to note that the introduction of Darwin-Mendelism occurred in England and America during a period of tumultuous economic and ecological change. Farming in both countries was undergoing a fundamental reorganization toward industrialized production for commercial markets. New varieties, new machinery, and new knowledge enabled growers to increase their output per hectare and per person-hour of labor. New lands were opened for farming in areas previously not farmed at all. New related technologies, such as railroads, made it possible to create a global network of markets for agricultural and other goods. Population increases and migration created turmoil for farmers everywhere. At the same time, shifts of people out of agriculture into urban factory work created mass markets for food. Pressures from these factors and others changed how the state regulated trade and the balance of power between the countryside and newly industrialized cities.

It is too simplistic to say that the profound changes of the nineteenth century "caused" Darwin and Mendel to propose their philosophy of variation and its transmission. At the same time, however, certain congruences and compatibilities appeared between the theories of Darwin and Mendel and the demands of the newly industrialized economies. Specifically, Darwin and Mendel brought a sense of order, prediction, and manipulation into the study of variation. These perceptions were critical to the construction of an agricultural plant science that served as the base for a complete industrialization and commercialization of agriculture. The parallels thus are useful in gaining an understanding of how plant breeding was constructed and what sorts of roles it came to play.

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