Kuhn’s theory of scientific revolutions remains influential in the explanation of modern science. Traditionally, the narrative of scientific development was often described in terms of “progress” and “culmination”. Kuhn’s theory, which emphasised periodization and disruption, thus provided a novel approach in our understanding of science – its fundamental workings, its progress and its challenges at an epistemological level. The primary features of Kuhn’s theory could be seen in terms of pre-paradigms, paradigms (or normal science), anomalies, crisis, post-crisis and revolutions.

Video describing Kuhn’s notion of paradigm shifts via metaphors.

Credit: nradke

Studying the complications

However, science remains an extremely diverse and broad discipline. There are certain challenges inherent when applying Kuhn’s model, as a way to explain the nature of science. There are instances in which discovering a “scientific breakthrough” or witnessing a paradigm shift is not straightforward. In reality, “anomalies” to the incumbent paradigm might not necessarily lead immediately to a paradigm shift. This could be the result of multiple factors (I will describe how so, later). It is also important that we define what “anomalies” are and recognize that its definition is not necessarily straight-forward. Thus, it is pertinent to examine the history of genetics and whether its course of development reflects these challenges. In sum, by examining these nuances, I hope to present the argument that the path towards the current paradigm of Mendelian genetics is not necessarily linear.

My methodology

I shall explore the applicability and limitations of Kuhn’s theory in light of the history of genetics by discussing the processes involved in each stage of its development.

It is the aim of this presentation to not merely describe the features of each stage, but more importantly, explain the inherent complications and contestations of how each stage is identified and moulded throughout time.

• Description of each stage
• How each stage fits with the history of genetics
• Critical lenses: Is this model / framework adequate?
• What are the limitations?

Pre-paradigmatic stage

Defined as a stage in which there was no fixed concept or interpretation, a “pre-paradigmatic” stage is crucial because it is the first step towards establishing a scientific approach – a path towards normal science. Relating this to the historical development of genetics, one could perceive the period leading up towards the establishment of the incumbent paradigm, Mendelian genetics, as the broad duration, in which the “pre-paradigmatic” stage occurred.

Yet, a more nuanced view reveals greater complications. In particular, the notion that multiple interpretations existed during this pre-paradigmatic stage, might be contested by the fact that a dominant paradigm actually existed, that of a “Blending theory of inheritance”. I would argue otherwise.  According to Portin, the “Blending theory of inheritance” was indeed very influential, with its influence being “in force for nearly two millennia” (Portin 2015, 16). Nevertheless, it is also instructive to point out that there are significant flaws in this school of thought. First, the “Blending theory of inheritance” was insufficiently conclusive, with an unsubstantial link between prediction and observation. For example, blending inheritance was unable to explain incidences of “discrete traits” (Fabian 2001, 2008). Second, and most importantly, the multiple conflicting theories that seemed to be directly indicative of blending inheritance theory, were actually largely based on speculation. Hippocrates or Aristotle had proposed theories that were indeed heavily influenced on blending inheritance theory, with Portin even terming these theories as “prior achievements” before the emergence of Mendelian genetics (Portin 2015, 16). Nevertheless, this was a period in which the theory of blending inheritance was not presented as a “universal” theory.  Thus, it would be more accurate to describe the theory of blending inheritance, less strictly in terms of a paradigm.

Perhaps, one way of defining a pre-paradigmatic stage is to determine the extent to which we could address and explain the phenomena at a very fundamental level. In other words, is there a consensus of basic laws or standards to which the community would employ to further elucidate the paradigm? Because the theories or concepts in the Pre-Mendelian period are grounded not in laws but more generally, speculation, we could then define this period as a “pre-paradigmatic” stage.

The Emergence of Mendelian genetics

Thus, the pre-paradigmatic stage in the history of genetics could be defined as a period, up until the emergence of Mendelian genetics, which concomitantly marked the origins of modern genetics as well as the the current paradigm. Yet, this notion of “modern” beginnings only began in the early 20th century. In fact, although Mendel had published his work in 1866, recognition of Mendel’s theory only started gaining recognition after his death (Dodson 1955, 187-194), which emerged only after DeVries, Correns and Tschermak had separately rediscovered the value of Mendel’s laws (Dodson 1955, 192).

Thus, the “emergence” of Mendelian genetics as a paradigm could be seen more accurately as a “re-emergence”. There are further complications in this narrative. In particular, while Darwin’s theory of pangenesis became obsolete since the re-discovery of Mendel’s laws, there was also a concerted attempt to re-mould Darwin’s natural selection theories, by incorporating it with Mendel’s laws (Zou 2014). The historical connection between Mendel and Darwin is indeed instructive in elucidating a critical feature of Kuhn’s theory. Namely, the attempt of scientists (who are working within a current paradigm) to redefine or modify Darwin’s anachronistic theory, in order to accommodate the principles of the current paradigm, reflects perhaps the inherently cumulative nature of how scientific knowledge is produced in paradigms. This was a point articulated by kuhn himself. “Perhaps the most striking feature of the normal research problem… is how little- they aim to produce major novelties, conceptual or phenomena” (Kuhn 1962, 35). In his paper, Vorzimmer even emphasized how both men were contemporaries and that Darwin’s initial theory would have stood, if he was cognizant of Mendel’s laws, as “the missing key” (Vorzimmer 1968, 77). This leads us to the next point, normal science.

Normal Science stage: Reinforcing the paradigm

 In normal science, the emphasis is on puzzle-solving. In other words, scientists aim to identify and reinforce the features of the dominant paradigm. One way of looking at this aspect of puzzle-solving is to see how the paradigm determines the problems to focus on, methods to use and finally, standards to evaluate the paradigm by.

In the context of Mendelian genetics, the focus is on identifying and demonstrating the hereditary factors (Sorsby 1965, 335). This presents the identification of the problem, in which subsequent methodologies and evaluation would be based on. Subsequently, after the problem is identified, the next feature would be the derivation of methodologies. In particular, this includes an array of extensive and systematic experiments, such as that of cross-pollination techniques. Methodology is vital in normal science, as employing good methodology would determine the strength and viability of the paradigm. To this end, because Mendel’s experiments and hypothesis were well-planned and explained, this presented the paradigm as an important precedent for future genetic research. For example, his experiments could be seen as fitting puzzle pieces in order to form a bigger picture. One way in which we could see Mendel’s effective use of methodology would be his selection of his model organism, the pea plant. The pea plant has advantageous traits that render it as an ideal model organism. Most importantly, these features include its high reproducibility, being easily manipulable and having both male and female parts (Sorsby 1965, 333).

Deichmann argued that another important feature of Mendel’s work pertains to his ability to craft his papers in a “clear and lucid style” (Deichmann 2010, 100). Last, perhaps we could also see the establishment of Mendel’s laws as a means of providing standards; a framework, in which geneticists working within this paradigm could evaluate its veracity (Portin 2015, 16).

Video showing Mendel’s laws

credit: PATRICKIRVINEable

https://www.youtube.com/watch?v=lppF8Mv4sbo

Could we view Non-Mendelian genetics as anomalies?

 Anomalies refer to “holes” in the paradigm, in which current methodologies are unable to explain. According to Kuhn, a crisis occurs when the accumulation of anomalies reaches a point, where the paradigm is unable to explain the phenomena. New research and discoveries in the field of genetics research have indeed posited questions examining the viability of the current paradigm. One important example pertains to the discovery of non-Mendelian genetics. This refers to variations such as incomplete dominance, codominance, multiple alleles and pleiotropy (Untamed Science, n.d.). According to Spillman, the main issue at hand here pertains to the basis that non-mendelian genetics are “cytoplasmic in character”, whereas mendelian genetics depend largely on the basis of the chromosomes (Spillman 1909, 437). Scientists supporting “non-mendelian” genetics often emphasize the insufficiency of the Mendelian paradigm in explaining these complications.

Video describing the priniciples of non-mendelian genetics

Credit: Teacher’s Pet

 Mendelian genetics still stands

Why is Mendelian genetics still our dominant paradigm?

Despite these anomalies, a paradigm shift has not occured. Perhaps, this is because these anomalies do not pose a direct challenge to the incumbent paradigm. Rather, we could see non-mendelian genetics, more as an extension of Mendelian genetics. For example, Silver argued that non-Mendelian genetics should be perceived within the context of existing Mendelian laws (Silver 2001, 1349).  From another perspective, this would also mean that non-Mendelian genetics should not be perceived as anomalies opposing the existing paradigm, since both Mendelian and non-Mendelian genetics actually belong to the “realm of the DNA theory of inheritance”, as elucidated by Portin (Portin 2015, 19).

 

References

Portin, Peter. 2015. “The Development of Genetics in the Light of Thomas Kuhn’s Theory of Scientific Revolutions.” Recent Advances in DNA and Gene Sequences 9: 14-25.

Fabian, J.R. 2001. “Transmission Genetics.” In Encyclopedia of Genetics, edited by Sydney Brenner and Jefferey H. Miller, 2008-2016. California: Academic Press.

Dodson, Edward.O. 1955. “Mendel and the Rediscovery of His Work.” The Scientific Monthly 81(4) :187-195.

Yawen Zou. 2014. “Charles Darwin’s Theory of Pangenesis.” Accessed November 15, 2018. https://embryo.asu.edu/pages/charles-darwins-theory-pangenesis.

Kuhn, Thomas. 1962. The Structure of Scientific Revolutions. Chicago: Chicago
University Press.

Vorzimmer, Peter. J. 1968. “Darwin and Mendel: The Historical Connection.” Isis 59 (1) : 77-82.

Sorsby, Arnold. 1965. “Gregor Mendel.” The British Medical Journal 1 (5431) : 333-338.

Deichmann, Ute. 2010. “Gemmules and Elements: On Darwin’s and Mendel’s Concepts and Methods in Heredity.” Journal for General Philosophy of Science 41 (1), Darwinism, Philosophy, and Experimental Biology (June 2010), pp. 85-112.

VanSomeren, Lindsay. 2017. “How do non-Mendelian genetics work?” Accessed November 15, 2018. http://www.untamedscience.com/biology/genetics/non-mendelian-genetics/.

Spillman, W.J. 1909. “A Case of Non-Mendelian Heredity.” The American Naturalist 43 (511): 437-448.

Silver, L. 2001. “Non-Mendelian Inheritance.” In Encyclopedia of Genetics, edited by Sydney Brenner and Jefferey H. Miller, 1349. California: Academic Press.