Ford, Edmund Brisco
Ford, Edmund Brisco
FORD, EDMUND BRISCO
(b. Ellislea, Dalton-in-Furness, United Kingdom, 23 April 1901; d. Oxford, United Kingdom, 21 January 1988),
genetics, ecological genetics, polymorphism.
Ford was a major contributor to the development of the modern synthesis in biology. He was a tireless exponent of the view that natural selection was the preeminent factor in shaping the evolution of natural populations. He created the field of ecological genetics, which is concerned with the experimental determination of the factors contributing to the adaptation and modification of wild populations in their environments.
Life . Ford was the only child of Henry Dodsworth Ford and Gertrude Emma Bennett. Although he spoke often of his father and they shared an interest in natural history, of his mother Ford said little, and nothing is known of her ancestry. Ford grew up in rural surroundings and early on became interested in archeology and natural history. At the age of eleven, he began to collect Lepidoptera (butterflies and moths), and in 1917 began a thirteen-year study, along with his father, of the relationship between the annual fluctuation in numbers and the observed varieties of a local population of butterflies that resulted in a joint publication in 1930.
In 1920, Ford was admitted to Wadham College at Oxford, where he studied classics and zoology. There he became acquainted with Gavin de Beer, Edward Bagnall Poulton, Ray Lankester, Leonard Darwin, Julian Huxley, and Ronald A. Fisher. While still an undergraduate, he published four papers, two with Huxley and one with Fisher. After receiving his BA, he did further research to obtain a BSc in 1927. He remained at Oxford as a demonstrator and lecturer until he was appointed the first reader in genetics in 1939. He was awarded a DSc in 1943, and in 1951, with the help of grants from the Nuffield Foundation, he founded and became director of the Genetics Laboratory. In 1963, he was appointed professor of ecological genetics. He retired in 1969. After his retirement, he remained active in research. His last scientific paper appeared in 1983.
During his long career, Ford received a number of academic and scientific honors. In 1946, he was made a Fellow of the Royal Society. He received the Darwin Medal from the Royal Society in 1954. In 1958, he was made a Fellow of All Souls College in Oxford, one of the few scientists since the seventeenth century to be so honored.
To his friends and collaborators, E. B. Ford was known as “Henry.” He was somewhat of an academic snob and name dropper with strong likes and dislikes. He had a lifelong interest in genealogy and heraldry and was known to recommend an entry from Debrett’s Peerage as appropriate bedtime reading. He never married. His students remembered him as a clear and meticulous, although idiosyncratic, lecturer. A number of amusing anecdotes illustrating his idiosyncracies can be found in Bryan Clarke’s biographical memoir for the Royal Society.
Background for Ford’s Achievements . The background for understanding the significance of Ford’s ecological research is the growing rapprochement in the 1920s and 1930s between Darwinian theory, centered on the role of natural selection in evolution, and Mendelian genetics, centered on understanding evolution in terms of the inheritance of genes.
At the beginning of the twentieth century, Mendel’s laws, first published in 1865, were rediscovered and the modern science of genetics was born. Mendelian inheritance involved the transmission of discrete factors or genes from parents to offspring. It soon became the model of choice for explaining the evolution of eye color, bodily markings, and other discrete traits. The Mendelian factors, or genes, were identified as components of chromosomes and geneticists began to work out the mathematical implications of the theory in conjunction with laboratory experiments that sought to identify the particular genes associated with particular organismal traits. Darwinism, with its commitment to continuous, not discrete variation, and its commitment to gradual changes over long periods of time, appeared to be at odds with Mendelism, and during the first decade of the twentieth century, Darwinism went into decline. From 1910 to 1920, it began to become evident that the conflict between Darwinism and Mendelism was only apparent. R. A. Fisher had begun to work out the mathematical details that would show that Mendelian inheritance was compatible with and explainable in terms of the slow action of Darwinian natural selection.
Ford was a committed Darwinian even before he went to Oxford. When he was an undergraduate, biology was at the beginning stages of what came to be known as the modern synthesis. His research was devoted to promoting that integration. In the 1920s, genetics research was confined, more or less, to laboratory experiments under controlled conditions. Ecologists, by contrast, were field workers who observed and recorded the behavior of organisms in their natural environments. Ford was a field naturalist who understood the importance of genetics and who had an interest in studying the genetics of the evolution of populations in their natural environments. During his long career, Ford was a tireless and often uncompromising proponent of the importance of natural selection for the evolution of genetic diversity in natural populations.
It is an undisputed observational fact that natural populations change over time. Population numbers fluctuate from year to year, varieties appear and disappear, new stable forms emerge and replace old stable forms, new populations arise and established populations become extinct. What was controversial in the 1920s and what remained controversial at the beginning of the twenty-first century is the relative importance of the processes by means of which these changes come about. The ultimate source of variation in populations is genetic mutation. Mutations, however, occur at random with respect to the environments in which organisms find themselves and thus are as likely to be deleterious as they are to be beneficial. Natural selection, by contrast, singles out those features of organisms that are best suited for the environments they find themselves in.
If one assumes, as did Ford and his colleagues, that natural selection had been operating over long periods of time to create populations that were fine-tuned to their environments, the chances of a mutation being beneficial were correspondingly small. One might expect natural selection to drive less fit alleles to extinction. However, in certain circumstances dominant and recessive homozygotes (the AA and aa forms) are less fit than the heterozygote form (Aa). In such cases, natural selection favors the heterozygote form and the net result is a stable population including both forms of the alternative alleles. This is what is known as “balanced selection.” In large populations, new varieties produced by mutation that were not as fit as others were liable to be swamped by the effects of natural selection and disappear in short order. In small populations, the chances are greater than a new variety will become fixed by chance alone. While R. A. Fisher was developing the mathematical theory of natural selection, Sewall Wright was constructing a theory that emphasized the importance of small populations and what came to known as random drift.
The task, as Ford saw it, was to demonstrate the effectiveness of natural selection in the wild as a major force in promoting and maintaining the diversity to be found in natural populations. Postulating the importance of natural selection in the wild was one thing, establishing it was another. Ford devoted himself to the development of concepts and tools that would enable researchers to establish once and for all that evolution by natural selection was not just a theory but was, in fact, the prime mover in the evolution of natural populations. This work led to the development of a new discipline that Ford called “ecological genetics.” In 1959, he identified this development as his “most important contribution to the evolutionary synthesis (Mayr and Provine, 1959, p. 341)
Early Research . Ford’s undergraduate work with Julian Huxley was on “rate-genes” in the sand shrimp Gammarus chevreuxi and culminated in five papers, two coauthored with Huxley. Their results indicated the importance of genes for controlling the timing and rate of developmental processes in different organisms.
The 1930 joint paper with his father H. D. Ford was based on thirteen years of observation and records dating back to 1881 of the population variation in a variety of butterfly found in several distinct colonies in Cumberland. The observations showed that the populations underwent a periodic fluctuation in size that was correlated with the degree of variation among types. When the population numbers were low, the variance in forms was low as well. As the population figures increased, so did the number of varieties. This increase was marked by the appearance of forms that would, under ordinary circumstances, seem to be nonviable. This was interpreted by Ford as evidence that the populations were under reduced selection pressures during the stages of population growth. At some point, the increased variation became stabilized around a number of new forms different from the variants that predominated in earlier peak populations. Ford cited this as evidence that natural selection was at work in natural populations.
In the 1930s, Ford adopted Fisher’s theory of the evolution of dominance. He showed that it was possible to experimentally select for both dominant and recessive traits in natural populations.
In the 1940s, Ford, in conjunction with Fisher, perfected the mark-release-recapture method. Specimens are marked with dabs of paint or dye, released into the wild, and recaptured at various intervals. The resulting data can then be used to make estimates of population size, migration patterns, and differential death rates. The relative recapture frequencies of different varieties were construed by Ford and his colleagues as evidence of the working of natural selection in the wild.
Definition and Explanation of Polymorphism . Ford’s first important theoretical result was his clarification and explanation of polymorphisms in natural populations. A polymorphism is a particular kind of variation. In 1940, Ford defined a genetic polymorphism as the coexistence of two or more forms of an organism that were distinctly different and existing at population levels that could not be attributed to chance. The condition that the forms coexist in the same locality rules out seasonal varieties and geographical varieties as examples of polymorphism. The condition that the forms are discontinuous variants rules out height differences as constituting polymorphisms. The requirement that the forms exist in proportions that cannot be explained in terms of recurrent mutation rules out rare diseases such as Huntington’s chorea as constituting a distinct human polymorphism. However, the sickle-cell trait occurs in a significant enough proportion of the human population to constitute a polymorphism in Ford’s sense. Similarly, Ford argued that the distinct blood groups constituted a polymorphism that was maintained by strong selective pressures. In his book Genetics for Medical Students, which first appeared in 1942, Ford argued that the existence of these polymorphisms had important implications for the treatment of diseases, on the one hand, and for the reality of human races, on the other.
Ford distinguished two kinds of polymorphism: balanced and transient. The balanced polymorphisms were held to be the results of balancing selective pressures. The implication was that there were strong selective pressures at work in nature—stronger than were thought to exist at the time. For example, consider the relationship between sickle cell anemia and resistance to malaria in humans. One of two alternative alleles involved in coding for hemoglobin leads to misshapen blood cells and a resulting anemia that lowers their fitness. Individuals with the normal allele do not develop anemia, but they are susceptible to contracting malaria, which also lowers their fitness. Heterozygotes are only mildly anemic but tend to be resistant to malaria. The net result is a population where the frequency of both alleles reaches an equilibrium. This is an example of what is known as “heterozygous advantage.” Another kind of ploymorphism is involved in the evolution of Batesian mimicry. In Batesian mimicry, innocuous organisms mimic dangerous or unpalatable models and thereby achieve some protection from predators. Because mimicry involves the evolution of co-adapted traits, Ford argued that the genetic basis of such traits most likely is a suite of co-adapted genes that constitute a so-called “super-gene.”
Ford’s conception of balanced polymorphism was criticized by Muller, among others. Muller took the concept of polymorphism, as understood by Ford, to be undermined by the rejection of the concept of “heterozygous advantage.” Muller’s view was that natural populations did not exhibit the extensive stable diversity required by ford’s concept of balanced polymorphisms. Field investigations established the fact that natural populations were more diverse than Muller and his supporters had thought. However, the explanation of that diversity remains controversial.
Transient polymorphisms, on the other hand, represented temporary coexisting forms resulting from selective pressures that, in time, would tend to eliminate one or more of the varieties. The case of the evolution of industrial melanism in the moth Biston betularia was held to be an example of this kind of polymorphism. Populations of these moths in nineteenth-century Britain tended to be primarily composed of a white variety. In areas of heavy industrialization with the attendant sooty atmospheres, melanic varieties began to be predominant. When pollution controls were put into effect, the white variety was reestablished as predominant.
The Peppered Moths . In 1951, Ford persuaded Henry Bernard Davis Kettlewell, a physician and amateur entomologist, to join him in the Ecological Genetics laboratory at Oxford in order to carry out field research that would further cement the role of natural selection in the wild. With Ford’s encouragement, Kettlewell conducted a series of field studies that appeared to show that the evolution of melanism in the moth Biston betularia was due to selective predation by birds. This result was immediately hailed as the long sought-after proof positive of the result of natural selection on wild populations. As such, it appeared in numerous textbooks as an iconic illustration of the truth of Darwinian evolutionary theory.
Criticisms and Reactions . In the 1960s and 1970s, techniques using gel electrophoresis and DNA hybridization were developed that revealed an unsuspected high level of variation in natural populations at the molecular level. These techniques for measuring genetic variability, unlike the field studies of Ford that inferred genetic variability from variation in expressed traits, were more direct measures of underlying genetic variation. Using the technique of gel electrophoresis, variation in proteins could be detected by having the proteins migrate through an electrical field on a gel. The heavier the protein, the slower it moved. Because the proteins were the direct products of genes, differences in proteins were inferred to be the result of differences in the underlying genes. The results showed that there much more variation at the protein level, and by implication, at the genic level than anyone had suspected. Initially, Ford was pleased by the new molecular techniques that were revealing that polymorphisms were even more abundant at the cellular level than the ecological studies had revealed.
However, it soon became apparent that there was, in fact, too much variation at the molecular level for it all to be maintained by natural selection. This situation raised the likelihood that other factors beside selection were at work. Indeed, the vast amount of variation at the molecular level led the evolutionary biologist Motoo Kimura to propose what he called the “neutral theory of molecular evolution” that held that much of the molecular variation did not have any selective significance. The fact that such polymorphisms existed in such abundance at the molecular level gave new impetus to Ford’s critics to reject his unilateral selectionist account of the evolution of the organismic polymorphisms detected in wild populations.
As a staunch defender of the important role of natural selection in evolution, Ford was at pains to reject any suggestion that the other evolutionary factors could have a comparable importance. In the 1920s and 1930s, the American geneticist Sewall Wright, one of the main architects of the modern synthesis, developed a mathematical model of what he called a “shifting balance” theory of evolution. This theory combined elements of genetic drift, or the random fixation of alleles in small populations, with natural selection. Wright suggested that some of the polymorphisms that Ford and his colleagues were discovering were, in fact, driven by the chance fixation of some variants in small populations that were then able to maintain themselves despite any overpowering by the forces of natural selection.
Ford would have none of it. He criticized Wright on the grounds that natural populations were larger than Wright’s models assumed were possible for random drift to be a major factor in their evolution. He and Fisher wrote a response to Wright’s criticisms in 1947 and dubbed Wright’s thesis the “Sewall Wright effect.” Both Ford and Fisher saw the opposition between their selectionist perspective and the alternative Wrightian view as polar opposites, either populations evolved through natural selection or by genetic drift. In fact, Wright never saw the dispute in such black and white terms; he argued that he had been misunderstood: The significance he attributed to random drift was not to be construed as a denial of the importance of natural selection. Evolution in Wright’s view was a “shifting balance” of contributing factors (Wright, 1948). Subsequent studies and calculations, however, suggested that both factors were playing a role in the evolution of natural systems.
In the 1960s and 1970s, opposition to the rigid selectionism endorsed by Ford began to mount. No one doubted that natural selection played a significant role in evolution but several questions remained open. For one thing, a general consensus was building that random drift and natural selection were both contributing to the evolution of natural ecologies. The question became not whether one or the other factors were significant but rather what the relevant significance of the two factors might be.
Moreover, there was mounting concern about the tendency of Ford and other selectionists to assume, without much tangible proof, that traits that became fixed in nature, including the polymorphisms, were the result of natural selection. Ford did not necessarily think that the polymorphic banding patterns in snails or the polymorphic spotted wing patterns on butterflies and moths were themselves adaptations. Rather, the presumption was that these features were the products of genetic complexes that had some selective value. This view was rejected by critics such as Richard Lewontin, Motoo Kimura, and Stephen Jay Gould, among others. In their famous and controversial paper, “The Spandrels of San Marco,” published in 1979, Gould and Lewontin labeled such a single-minded conviction in the efficacy of natural selection, the “adaptationist programme.”
Major Work . Ford’s magnum opus was his book Ecological Genetics, in which he summarized his life’s work. First published in 1964, it went through four editions in his lifetime. His general conclusions were, first and foremost, that there were powerful natural selection forces operating in nature. Second, he felt that he had established that any effects of random drift in natural populations would be overwhelmed by the effects of selection. Third, although mutation serves as the original source of variation, living organisms are the products of evolution controlled not by mutation but by powerful selection. In this respect, he was a lifelong defender of what came to be labeled as panselectionism and the adaptationist program. Fourth, in light of his commitment to the significance of selective forces in the evolution of biodiversity, he held that the ecological conditions that have promoted the evolution of life on Earth have to be assumed to be special. Ford drew some cosmic conclusions from his commitment to the view that life on Earth was the product of strong selective pressures acting over huge time intervals. He argued that it was very unlikely that any similar sequence of events had or would occur elsewhere in the universe, and hence that life as humans know it on Earth is very probably unique. Fifth, he saw the primary task of ecological genetics, as he understood it, to lie in establishing that natural selection in the wild is indeed the main factor in the coevolution of organisms and their environments. Sixth, the polymorphisms responsible for Batesian mimicry in nature is to be attributed to the action of “super-genes,” that is, coordinated genetic systems that have multiple effects.
Finally, the application of the polymorphism concept to human beings indicated the importance of genetics for medicine. In particular, Ford argued that the fact that human blood group polymorphisms were under balanced selection showed that there were powerful selective forces at work maintaining the differences between human populations. Ford suggested that this had significance for understanding the susceptibility of different human populations to different diseases, which he felt would contribute to the development of racial, that is, populational, medicine.
Popular Works . In addition to his scientific papers and technical works, Ford wrote a number of popular works for the general public. Among the most significant were two guides, one on butterflies (in 1945) and one on moths (in 1955), that he wrote for the New Naturalist series, a collection of works aimed at promoting an awareness and appreciation of science among the British public. Ford’s two contributions were aimed at amateur collectors and entomologists but unlike most such guides, they contained a fairly heavy dose of genetics and theory.
Ford returned to the social implications of genetics in a book written for the educated layperson or specialist, Understanding Genetics, which appeared in 1979. There he reiterated his view that the existence of stable human polymorphisms was evidence of both the reality of human races and the significance of understanding the differences between races for the treatment of diseases. In addition, he suggested that the fact that human intelligence had a genetic basis meant that because there was genetic variation for intelligence from one individual to the next, this result could be extrapolated to conclude that the average intelligence of different races was bound to differ as well. In addition, he saw the genetic basis of variability in intelligence as a ground for what he called “hereditary social distinctions” in society.
WORKS BY FORD
With Henry Dodsworth Ford. “Fluctuation in Numbers and Its Influence on Variation in Melitaea aurina.” Transactions of the Entomological Society of London 78 (1930): 345–351.
Mendelism and Evolution. London: Methuen, 1931. 8th ed. 1965.
“Polymorphism and Taxonomy.” In The New Systematics, edited by Julian Huxley. Oxford: Oxford University Press, 1940.
Genetics for Medical Students. London: Methuen, 1942. 7th ed., 1973.
Butterflies. New Naturalist Series. London: Collins, 1945.
Moths. New Naturalist Series. London: Collins, 1955.
Ecological Genetics. London: Methuen, 1964.
Understanding Genetics. London: Faber & Faber, 1979.
Cain, Arthur J., and William B. Provine. “Genes and Ecology in History.” In Genes in Ecology: The 33rd Symposium of the British Ecological Society, edited by Robert James Berry, T. J. Crawford, and G. M. Hewitt. Oxford: Blackwell Scientific Publications, 1992.
Clarke, Bryan. “Edmund Brisco Ford.” Biographical Memoirs of Fellows of the Royal Society 41 (1995): 147–168. Contains an extensive bibliography of Ford’s publications.
Creed, Robert, ed. Ecological Genetics and Evolution: Essays in Honour of E. B. Ford. Oxford: Blackwell Scientific Publications, 1971.
Gould, Stephen Jay, and Richard Lewontin. “The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme.” Proceedings of the Royal Society of London, Series B, Biological Sciences, 205 (1979): 581–598.
Mayr, Ernst, and William B. Provine. The Evolutionary Synthesis: Perspectives on the Unification of Biology. Cambridge, MA: Harvard University Press, 1980.
Provine, William B. Sewall Wright and Evolutionary Biology. Chicago: University of Chicago Press, 1986. Contains a discussion of the controversy between Ford and Sewall Wright.
Wright, Sewall. “On the Roles of Directed and Random Changes in Gene Frequency in the Genetics of Populations.” Evolution 2 (1948): 279–294.