Kevin Elias History and Science 97b
From Without to Within Kenji Ito


From Without to Within:
The Transition of Evolutionary Mechanism
from Natural Selection to Genetics


Kevin Elias
History of Science 97b
05/11/01
Kenji Ito
Wednesday 7-9


Introduction
When one opens any contemporary text on the working of evolution, scarcely a minute’s worth of perusing is necessary before the term “gene” hits the reader’s eye with unrelenting frequency. Indeed, genetics has become the foundation of modern evolutionary thought. Yet, when Charles Darwin was outlining his theory of evolution in the mid-nineteenth century, he made no mention of genetics for the very simple fact that the field did not exist. While that little insight might seem glaringly obvious in its simplicity, it begins to unearth some very interesting questions in the history of science. What were the circumstances wherein evolutionary theory became intertwined with genetics? How did the nature of evolutionary work change when genetics became involved? Much like genetics and evolution, these two questions are inextricably spun around one another.
I contend that evolutionary theory under Darwin was fundamentally different from evolutionary theory under the geneticists. The transition was incremental. First, Darwin’s theory of natural selection came under assault by August Weismann and William Bateson in the late nineteenth century. They concluded that natural selection was true as far as it went, but that this was probably not very far.[1]
Next, there was the rediscovery of Mendel. Bateson and Hugo De Vries realized that heredity and the Mendelian technique held promise for understanding how evolution really worked. Finally, natural selection became subservient to the more important evolutionary mechanism of mutation. De Vries and Thomas Hunt Morgan then defined the experimental parameters of this phenomenon. After this last phase, a new theory of evolution emerged. The mechanism of mutation replaced natural selection as the primary wheel steering the workings of evolution.
I believe that historians of genetics have not properly considered the introduction of Mendelian genetics into the evolutionary arena. Peter J. Bowler points out that the majority of works by professional historians of science regarding turn of the twentieth century biology reflect "a certain whiggishness."[2]
They focus almost entirely on the aspects of Darwinism and Mendelism that would later bear fruit for the so-called evolutionary synthesis,[3]
while little work has been done on evolutionary work at the time that did not contribute directly to the modern stance on evolution. I distinguish the present account from previous work on the subject by nature of the fact that the traditional telling of the history of evolutionary science takes for granted that the incorporation of genetics into evolutionary theory was a simple modification of the preexisting evolutionary ideas. Indeed, Michael T. Ghiselin suggests that any seeming gulf between genetics and natural selection was never that great. He offers a history wherein genetics actually served to hinder modern evolutionary theory by forcing a reconsideration of alternative theories to natural selection that would later be dismissed.[4]
I disagree with Ghiselin's assessment as to the insignificance of this gap between evolutionary theory under natural selection and what I see as a new evolutionary theory put forth by the geneticists. Contrary to the Ghiselin thesis, I propose that in the early twentieth century Darwin’s theoretical account of evolution was not modified by the rediscovery of Mendelian inheritance; rather, the entire natural selection theory was replaced with a radically different approach to evolution created by William Bateson and the other early geneticists.
I distinguish the geneticist theory from the selectionist theory by two key characteristics. First, natural selection theory was entirely based on observation in the field, while genetic theory was based on experiment in the laboratory. While the former was overtly qualitative in nature, the latter strove to be as quantitative as possible. Second, while natural selection was seen as an external force that acted on populations of a species, genetic variation was seen as an internal force that was an organic part of an individual organism. The theory of natural selection was essentially metaphysical in character in that it was a force of nature and not a principle that could be shown to work by a rational mechanism. In contrast, the theory of natural selection contained a spatial-temporal mechanism by which the workings of evolution were understood to be a physical part of organisms and could be followed over a period of generations. The result of these differences between the theory of evolution before and after Mendel was that a completely new theory of evolution emerged that could address not only the phenomena of the Darwinian account, but also a whole host of new questions previously outside the bounds of evolutionary science.

Evolution According to Natural Selection
Establishing that genetic theory was a replacement of selectionist theory rather than a modification of it requires a somewhat descriptive account of history to provide the proper context.[5]
We start with the theory of evolution in the late nineteenth century. Darwin had created a fundamentally new science. For the first time, a mechanism, natural selection, was employed to explain the variation among and within species. Darwin understood selection as individuals "having any advantage, however slight, over others, . . . have the best chance of surviving and of procreating their kind."[6]
Over time, these advantages, or “adaptations,” as Darwin called them, would accumulate sufficiently enough for one to be able to distinguish a new species, clearly different from the original form. By a close study of species adaptation, Darwin expected that a rational system for explaining the origin of all species would emerge. In his view natural selection was the primary mechanism for creating new species. Later, this would become a key point of dispute for the geneticists. I detect a sense of disagreement in William Bateson's observation that in Darwin's view "specific diversity had no physiological foundation or causation apart from fitness."[7]


Problems with Darwin's Theory of Natural Selection

While Darwin was able to call natural selection the primary force dictating the development of species, he still was not able to remove all vestiges of previous theories on the origin of species. Most importantly he conceded that the “heredity transmission of parental experience and its consequences” [8]
had some role in the origin of species, but “with his habitual caution refrained from specifying [how great a role], for the sufficient reason that he did not know.”[9]
This omission, however, prevented Darwin's theory from getting clear of the proposals of J. Lamarck. At the beginning of the eighteenth century Lamarck had put forth a theory that the origin of species was due entirely to the inheritance of acquired characteristics. Darwin's openness to the ability of traits to be transmitted by virtue of use or disuse exposed him to attacks from a biological community that was reluctant to accept this postulate.

The Need for Experiment

A leading assailant of Darwin on the point of acquired characteristics became August Weismann. Weismann was a German biologist and junior contemporary of Darwin. While supporting evolution, he could not accept the inheritance of acquired traits. In a famous experiment, he cut off the tails of five generations of mice, 901 mice in all, and yet the progeny of every mouse grew normal tails. He challenged the scientific community for evidence that acquired traits have any transmitted effects at all, but none of any merit was ever produced. Though it was only a minor point of Darwin’s theory, the collapse of acquired traits had a lasting effect on future biologists. First, it cleared the ground for the construction of a new theory of heredity.[10]
,[11]
Most importantly, it began to illustrate the weaknesses of a theory based solely on observation and not experimental fact.
This lack of experimental evidence arose from the shift of evolutionary work after Darwin from physical concerns to theoretical matters. While Darwin had explained the role of variations in the struggle for life, he could not account for the physical causes of the variations themselves. Consequently, the vast majority of evolutionary work done in the latter half of the nineteenth century focused on the historical problems of evolution, rather than the causal ones. Evolutionists turned to compiling phylogenetic evidence to support the theory. For example, much effort was put into fieldwork and the cataloguing of examples of variation and adaptation. I suggest that the movement away from any experimental work was due, at least in part, to the rash of popular issues raised by evolution, as evidenced by popular evolutionary accounts more interested with theoretical aspects and opinion than with method.[12] Lock suggests that even the majority of specialists gave up the experimental method in favor of the controversial one for the fifteen to twenty years following the acceptance of the theory of natural selection.[13]
As the century wore down, William Bateson led a movement to return evolutionary biology to the realm of experimental investigations.[14]
Bateson was an English biologist educated at Cambridge. He was especially bothered by a system wherein natural selection acted like a disconnected, metaphysical force. In 1894 he published his theory of discontinuous variation. A precursor to the mutation theory of De Vries, Bateson used experimental breeding of plants and animals to show that evolution did not take place via continuous variation through the generations as Darwin had suggested. Instead variations sporadically appeared and disappeared. The experiments made it apparent that Darwin’s mechanism of inheritance would actually be fatal to his theory of evolution if one attempted to use it to explain the breeding experiment data. Lewontin explains that if inheritance were of the continuous or blending form, then sexual reproduction would result in a reduction of the variance in the population by a factor of one-half with each generation. When this fact is combined with Darwin’s theorem that advance under selection is limited by variance in fitness, it immediately becomes obvious that evolution would be impossible in sexually reproducing organisms.[15]

The Movement for a Quantitative Analysis

I contend that the complications raised by the breeding experiments seemed to highlight larger ambiguities associated with the qualitative nature of natural selection. Bateson was highly critical of the fact that one could “never make any quantitative estimate of the amount of benefit or the reverse which any particular structure may afford its possessor.”[16]
There was no benefit in assuming that every variety was an adaptation of some sort if there was no way of measuring how much of a benefit that trait impressed. For example, how could one measure the benefit of a bird being brightly colored for mating purposes against the benefit of it having drab colors to escape predators? Furthermore, if every trait was an extension of another trait, how could new organs develop?[17]
The math did not agree with Darwin, either. Calculations as to the possibility of natural selection alone bringing about a new race showed that it would never happen.[18]
Darwin’s views, while theoretically persuasive, upon technical analysis, seemed weak.

The Species Problem

Bateson also had serious problems with Darwin’s antiquated definitions of variation, species, and heredity. The ambiguity between species and variety resulted from the system under which classification of species had been conducted prior to Darwin's time. Naturalists classified organisms for convenience of reference. The term species had no technical basis. As Bateson points out, "if anyone had asked them what they meant by a species, it is practically certain that they would have not the slightest idea what the question might imply, or any suspicion that it raised a fundamental problem of nature."[19] Naturalists were much more concerned with the descriptive work of identifying organisms and much less concerned with the overarching order to any system that was created.
The taxonomic system of Carolus Linnaeus, however, sought exactly this rigidity that the naturalists had not. Debates broke out with regards to what was a "good species" versus a "bad species." The whole process lay entrenched in subjectivity. Any one feature of an organism, whether its color, sex characteristics, or structural differences, could be enough to merit a new species or to lump together a whole series of organisms as belonging to one species. Rather than being a minor issue of particulars, the exact denomination of every species formed the backbone of the entire systematist philosophy. Because they claimed that every species could be found and named, the Linnaen writings induced the conviction that the species of animals and plants were immutably fixed.[20]
Linnaeus’s definition of a species as that entity which owed its origin to a “separate act of creation” helped further this idea.[21]
Even opponents to the immutability of species failed to resolve the species-variety conflict. For example, Lamarck incorporated the difficulty of distinguishing species from varieties as part of his evidence for species transmutation.[22] Without an association with physical phenomena, however, no one approached the species issue with the mechanistic base that an explanation of the origin of life required.
Darwin took on this task. He presented adaptation as the physical definition of species. By seeing how two closely allied species had utilized different adaptations to survive, he believed one could distinguish one species from the other. This line of adaptations, then, would trace the paths of common descent among species. By a close study of species adaptation, Darwin expected that a more rational system for naming species would emerge.
While Darwin succeeded in demonstrating variation among divers species, Bateson showed that he failed to adequately address the species-variety dilemma. For Darwin, species had not yet taken on theoretical importance in that the fundamental units of classification had not yet become the fundamental units of evolutionary theory.[23]
Bateson's criticisms of this omission can be seen as another example of Bateson's desire to frame evolution in quantitative terms. First, Bateson argued that variations were found to exist in a much greater abundance than Darwin had anticipated. Second, species could still be distinguished by any variety of features, many of which had no apparent role as adaptations. Third, a single "species" might be subject to so much local differentiation, as to make it impossible to state which variations connoted new species and which were polymorphisms in the population.[24] Fourth, variations could be compounded by hybridization of races, giving intermediates that had not previously existed. Finally, the mechanism of selection could not explain how two different strains of the same species could exist side by side.[25] Surely, natural selection should have been seen eliminating the less adapted strain in favor of the more adapted one. Taken together, these faults raised a paradox: How could selection be such a loose process but speciation be so precise? Evolutionary theory could not reject its emphasis on the fluid nature of species; it had to find some new mechanism for explaining the transmission of favorable traits.

The Effect of Mendel

In 1900 the rediscovery of Mendel’s breeding experiments dropped the answer into the laps of the biologists. Gregor Mendel was an obscure Austrian monk with a deep interest in botany. In 1865 he reported his findings on some curious phenomena of plant hybridization. What made this work unique was the meticulous precision with which Mendel carried out his experiments. Mendel was convinced that among all the experiments performed by his predecessors, "not one [had] been carried out to such an extent and in such a way as to make it possible to determine the number of different forms under which the offspring of hybrids appear, or to arrange these forms with certainty according to their separate generations, or definitely to ascertain their statistical relations."[26] In a footnote, Bateson points out that Mendel defined a well-reasoned investigation of heredity by its examination of the number of different offspring forms, their classification by generations, and their statistical relationship.[27] The novel combination of these points of inquiry marked the success of Mendel's work.
Despite what Bateson in 1900 realized were significant advances for biology, Mendel's papers in their original publications received no notice from the scientific community. The reasons for this oversight have been much debated. Bateson points out that the Brünn Society exchanged publications with most of the European Academies, so obscurity of publication cannot be considered an overriding factor.[28]
I propose a more likely explanation. At this time the biological community was still overwhelmed by the writings of Darwin. Darwin's writings were markedly observational and hypothetical in character, while Mendel's work was fundamentally experimental and physical.[29]
Mendel's work was overlooked because it did not follow the style of a contemporary species paper.
The profound effect of Mendel's writings on Bateson and other biologists studying heredity is difficult to understate. At the time, Mendel's ideas were completely novel. While Mendel had not been writing in reference to evolution, biologists like Bateson in 1900 were convinced that heredity and experiment could be used to explain evolutionary concepts. Mendel made it abundantly clear to Bateson that further progress was contingent on actual experiments in breeding.[30]
Not only did this confirm Bateson’s notion that heredity played a key role in understanding evolution, but Mendel's work also outlined a new scientific process by which one could examine the inheritance of traits over several generations. Mendel showed that statistical analysis could be used to predict the appearance of "character" traits.

Evolution and the Gene

The most striking element of Mendel's work was this concept of "characters" effecting the expression of physical traits. The "character" concept, later called the gene, broke down heredity from the study of individuals to the study of independent characters that those individuals possessed. Mendel proposed that each organism contained a "pair of different characters in hybrid union," one of each inherited from the parental stock.[31] These characters could be assigned variables and mathematically assessed. This allowed Mendel to predict all the possible combinations of characters that a plant with parents of a known character-type (genotype) might possess. He was then able to show that the ratios of traits predicted by this mathematical modeling were in fact the true proportions of physical expressions in his plants.
Through careful collection of data, Mendel was able to formulate the conclusions that became the foundation for Bateson's work. First, he postulated a segregation of characters in the male and female germ cells of hybrid plants. Each germ cell contains only one member of the pair of differentiating characters present in each parent. Each member of such a pair of characters is represented in an equal number of germ cells of both sexes.[32] Second, he put forth the law of independent assortment. This means that separate pairs of differentiating characters are inherited independently of one another. In other words, the inheritance of one trait does not preclude the inheritance of another.

A Physical Mechanism for Evolution

A key element of Mendelism was that it designated the actions of a particulate entity as the mechanism for evolution. Natural selection had put the origin of species in the hands of a supernatural force that had no physical manifestation. For Bateson there was a simple beauty in Mendel’s ideas. He preferred the “cosmic” Mendelism to the “chaotic” natural selection.[33] The order of the system meant that “no matter how low in the scale we go, never do we find the slightest hint of diminution in that all-prevailing orderliness, nor can we conceive an organism existing for a moment in any other state.”[34] The metaphysical natural selection was replaced with the physical genetics.

Application of Mendelism

Mendel's ideas brought about a radical change in the way biologists understood the mechanisms of heredity. The experimental evidence offered by Mendel's techniques allowed them to escape the theoretical difficulties that had begun to obscure their understanding of evolution.[35] First, Mendelism solved De Vries's problem of a new trait being bred out of the population before it could have any evolutionary effect. With the concept of heterozygous characters, a recessive trait could continue to be passed on through the generations even if it was not being expressed. Eventually, a homozygous recessive individual would arise who would again express the new trait.[36] Furthermore, Mendel's conclusions offered an explanation for the preponderance of observable variations within species. Lewontin shows that the fewer characters needed to control a trait, the more likely it is that a new trait can develop. By suggesting that "the number of particles controlling a character is the absolute minimum" Mendel was able to show that the possibility for evolution is maximized.[37] Identifying these characters and following their inheritance through several generations would be the great new pursuit for evolutionary biology.

Mendel's Work Brings a Return to Experiment

The novelty of Mendel’s discoveries and analytical approach began a rash of experimental work in genetics. Bateson introduced the term “genetics” to describe the investigation of heredity through Mendelian techniques. [38]
The field was characterized by an amalgam of Bateson, Mendel, and Darwin. Bateson continued to employ his theory of discontinuity to characterize the distribution of variations in a population. From Darwin came the axiom that the specific form of organisms fit the places where they lived. This proposition was important for explaining how one variation might be selected over another. The quest then was to discover the mechanisms by which variation happened and the conditions that caused these mechanisms to occur. Geneticists knew that Mendel's characters provided the physical mechanism whereby variations were inherited. Furthermore, geneticists realized that his experiments provided the model for future progress in understanding why these variations occurred.
Bateson's experimental approach to answer these questions was a novel combination of four methods of study. First, he continued to directly compare organisms. Second, he used statistical examination to chart the distribution of genetic traits. Third, he did cultural experiments. The idea was to raise as many of the organism as possible and to watch for variations to occur. Finally, once variations were found, he performed Mendelian crossbreeding experiments to see how the trait was inherited. Bateson channeled his enthusiasm for genetic theory into creating the first center for genetic research at Cambridge. He and his lab became the recognized authority on genetic work.[39]

The rash of genetic research that followed was linked to a growing movement by younger biologists to return biology to the experimental sciences. Garland Allen suggests that prior to 1900, these biologists were painfully aware of how few of the accepted generalizations in biology could be tested by experiment.[40]
The movement to ground evolutionary theory in experiment was part of a larger movement by the generation of post-Darwin biologists to have biology follow the example of chemistry and physics and to put these generalizations to a clear experimental test.

A New Approach to Species and Variety

Reconciling Mendel to evolutionary theory also meant that biologists had to reexamine their definitions of species and variety. This meant replacing the qualitative approach of Darwin with the quantitative approach of Mendel. Bateson saw it as exceedingly unlikely that the difference between species and variety would continue to be defined as a matter of degree.[41] While Darwin had defined any variation between parent and offspring as a variation, the understanding of Mendelian principles forced the geneticists to adopt a more precise definition. Bateson supported De Vries’s principle that “real, genetic variation” had to be distinguished from “fluctuational varieties, due to environmental and other accidents, which can not be transmitted.”[42] ,[43] The only way to do this was exhaustive research. In the end, Bateson hoped to prove that variation and heredity were real phenomena instead of mere axioms for theoretical discussion.[44]

Mutation Theory

Ultimately, Hugo De Vries proposed the mechanism that would unite variation, heredity, evolution, and experiment into a unified theory. De Vries's methods modeled the new form of biological experiment popular among the young generation of biologists at the turn of the century. In 1900, De Vries was one of three researchers who affirmed the accuracy of Mendel’s experiments. Since 1886, he had been studying the appearance of variations in his cultivations of the evening primrose. He realized that these new variations were not merely passing differences that could be explained by environmental factors, but rather they were new traits that could be bred into future generations. He called these spontaneous variations “mutations.” He summarized his theory in his 1901-3 treatise Die Mutationstheorie, or The Mutation Theory. What distinguished mutations from fluctuating variations was that mutations signaled permanent evolutionary change. He used breeding experiments to show that mutation could be seen as a genetic distinction between varieties and species. A mutation could not be blended away. It was instead a physical part of an organism’s makeup.
An explanation of evolution through mutation represented a radically different view of evolutionary processes than had natural selection. Bateson eventually seized onto De Vries’s mutation theory as the mechanism underlying his theory of discontinuity. He realized that whereas Darwin erroneously saw evolution as “the gradual transformation of masses of individuals by the accumulation of impalpable changes . . . the facts of heredity and variation [united] to prove that genetic variation is a phenomenon of individuals.”[45] De Vries extended this contrast even further. While natural selection had called for a gradual development of new species, his theory suggested that “species arise by a sudden step in which either a single character or a whole set of characters together become changed. In the former case a new variety is the result, in the latter a new species. . . is produced.”[46]

The Extension of Mutation Theory

What De Vries started with plants, Thomas Hunt Morgan continued with animals. Morgan was an American zoologist. He bred fruit flies in large quantities, and in 1909 observed the spontaneous mutation of a fruit fly from red-eyed to white-eyed. As his work became published and his fame grew, the conception of evolution changed forever. No longer was evolution explained through populations or even individuals, but only through genes. In less than two decades evolutionary work had changed from the study of populations to the study of the “independent characters of which the individual is made up.”[47]
Morgan predicted that in the future “relationship by common descent will be recognized as of minor importance as compared with relationship due to a community of genes.”[48]
Morgan was right. A new concept of evolutionary theory emerged wherein genetic mutations were the primary mechanism of evolution and selection was relegated to a secondary role. As Bateson said, “selection determines along which branch Evolution shall proceed, but it does not decide which novelties that branch shall bring forth.”[49]
Moreover, the characterization of natural selection changed. Natural selection was no longer seen as the stern judge holding species to the exacting standard of survival of the fittest. Instead selection was seen as a more lenient taskmaster that could permit distinct varieties of the same species to exist indefinitely side by side.

Conclusion

We began our discussion with the questions of how genetics became a part of evolutionary theory and how evolutionary work changed as a result of the genetic influence. Prior to 1900, difficulties were arising with the acceptance of Darwin’s view of evolution. Darwin’s inclusion of inheritance of acquired traits, his vague distinctions between variety and species, and the dubiousness of natural selection being able to bring about a transmutation of species on its own, raised questions as to the solidity of Darwin’s account. Without an overarching counter-theory, however, natural selection remained the primary mechanism by which species were thought to develop.
The rediscovery of Mendel’s papers presented the first experimental evidence that Darwin’s theory was fatally flawed. William Bateson, Hugo De Vries, and Thomas Hunt Morgan exploited the experimental focus of Mendel’s work to steer biology away from Darwin’s focus on theory back to a tradition of experimental analysis. They changed the research work done in evolutionary science from collecting expeditions in the field to breeding experiments in the lab. Through their investigations, they produced the evidence for a mutational theory of species origin. While natural selection was kept as an agent in evolution, no longer was selection seen as having any influence on the formation of species themselves.[50]

I maintain that this approach to evolution was radically different from that which Darwin had proposed. Bowler confirms that there had to have been some sort of significant schism between the two types of evolutionary thought since "if Mendelian genetics and the Darwinian selection theory so obviously complemented each other . . . it is strange that biologists took several decades to recognize the fact."[51]
Indeed there was no complementarity. The mutationists interpreted Mendel’s work as implying a “definiteness and specific order in heredity and therefore variation. This order [could not] by the nature of the case be dependent on Natural Selection for its existence, but [had to be] a consequence of the fundamental chemical and physical nature of living things.”[52]
The simple beauty of a set of characters found in every organism overthrew the omnipotence of natural selection. The natural selection theory -- theoretical, qualitative, and metaphysical -- was overtaken by the genetic theory -- experimental, quantitative, and spatial. Since it captured the throne of evolutionary science, genetics has yet to relinquish its grasp.

[1] William Bateson, Darwin and Modern Science, published in William Bateson, F. R. S., naturalist; his essays & addresses, together with a short account of his life by Beatrice Bateson (Cambridge University Press, 1928), p. 217.

[2] Peter J. Bowler, The Eclipse of Darwinism, (Baltimore: Johns Hopkins University Press, 1983), 6.

[3] The evolutionary synthesis is the name given to the great resolution in the 1930's that reconciled the discrepancies between Darwinian theory and advances in genetics.

[4] Michael T. Ghiselin, Metaphysics and the Origin of Species, (Albany: State University of New York Press, 1997), 3-4.

[5] The reader will please see this narration as necessary for a proper understanding of my arguments, which I have done my best to make explicit.

[6] 2 Charles Darwin, The Origin of Species by Means of Natural Selection or the Preservation of Favored Races in the Struggle for Life (Chicago: W.B. Conkey Company, 1915), 99.

[7] William Bateson, Problems of Genetics (New Haven: Yale University Press, 1913) 11.

[8] Bateson, Darwin and Modern Science, p. 220.

[9] Ibid.

[10] Ibid., 211.

[11] Weismann also had a positive contribution to genetics. He proposed a theory of heredity based on cellular entities called “germ plasms.” Though similar to later chromosomal accounts, it was later disproved, but his ideas stimulated much of the work in early twentieth century cytology.

[12] Robert Heath Lock, Recent progress in the study of variation, heredity, and evolution (London: J. Murray, 1920), 3.

[13] Ibid.

[14] "In the last decade of the nineteenth century many of us perceived that if any serious advance was to be made with the group of problems generally spoken of as the Theory of Evolution, methods of investigation must be devised and applied of a kind more direct and penetrating than those which after the general acceptance of Darwinian views had been deemed adequate." Bateson, Problems, 1.

[15] R.C. Lewontin, “The Gene and Evolution.” Published in Mendel Centenary: Genetics, Development and Evolution. Edited by Roland M. Nardone Proceedings of a symposium held at the Catholic University of
America, November 3, 1965 (Washington : Catholic University of America Press, 1968), 68.

[16] Lock, 60.

[17] Lock gives several specific examples along these lines p. 60-5.

[18] Lock, 136. De Vries argues that while some variation would be visible at first, the full possible effect of selection for the trait would be exhausted in only a few generations. After that, selection would just keep up that standard.

[19] Bateson, Problems, 4.

[20] Bateson, Problems, 8-9.

[21] Lock, 7.

[22] Darwin, The Origin, 5.

[23] Ghiselin, Metaphysics, 5.

[24] Bateson, Problems, 14.

[25] Bateson, Problems, 134.

[26] Mendel, Experiments in Plant Hybridization, reprinted in William Bateson's Mendel's Principles of Heredity (Cambridge: University Press, 1909), 318.

[27] Bateson, Mendel's Principles, 316.

[28] Ibid.

[29] The lack of association between the authors was definitely a factor in their choice of method for scientific inquiry. Mendel had begun his work before Darwin published his theory of natural selection, and there is little evidence to show that Darwin's work had any real influence on Mendel's thought processes. The reverse was also the case. Darwin was unaware of the work of Mendel. Even though he apparently did read the work of other experimentalists in the field of heredity, their data and technique were so imperfect as to be duly neglected.


[30] Bateson, Darwin, 222.

[31] Mendel, Experiments in Plant Hybridization, reprinted in Bateson's Mendel's Principles, 337

[32] Lock 191.

[33] Bateson, Darwin, 223.

[34] Ibid.

[35] Bateson, Darwin, 221.

[36] On this note, Lock suggests that the phenomenon of segregation led to a reconsideration of the term "purity" in biology. By this he means that with the concept of recessive traits, the length of time that a race had displayed a character did not rule out the possibility that the individuals for that race were heterozygous for that trait. A seemingly "pure" line might carry an "impure" trait.

[37] Lewontin, 69

[38] I have tried to be historically accurate with my uses of the terms "gene" or "character," but it very difficult for a modern commentator to avoid anachronisms in these terms. I apologize if this ever causes confusion.

[39] Lock, x.

[40] Garland Allen, Life Science in the Twentieth Century (New York: John Wiley and Sons, Inc., 1975), xv.

[41] Bateson, Darwin, 225.

[42] Ibid.

[43] Bateson expressed a sense of relief that Darwin had not known of Mendel, for the knowledge of the variety problem might have prevented him from being bold enough to publish his theory of natural selection. He points out that it is much easier to put faith in a random, insensible mechanism that to attempt to elucidate an intricate orderly system.

[44] Bateson, Problems, 1.

[45] Bateson, Principles, 289.

[46] Lock, 153.

[47] Lock, 220.

[48] Thomas Hunt Morgan, The Physical Basis of Heredity (Philadelphia: J. B. Lippincott, 1919), 223.

[49] Bateson, Darwin, 227.

[50] Lock, 157.

[51] Bowler, Eclipse, 16.

[52] Bateson, Darwin, 223.