Portal de Periódicos da CAPES

Hybrid Teaching

2023; Duke University Press; Volume: 97; Issue: 4 Linguagem: Inglês

10.1215/00021482-10795905

1533-8290

Matthew Holmes,

American History and Culture

This special forum highlights innovative and diverse methods of teaching agricultural history. Yet agricultural history itself can also help inform how we teach difficult topics. Take, for instance, one of the most discussed intersections between the history of agriculture and the history of science: the 1900 “rediscovery” of Mendelian genetics and its application to early twentieth-century plant breeding.1 Despite its omnipresence in contemporary textbooks and classrooms, Mendelism can be hard to understand. A 2018 study of undergraduate students at Creighton University found no difference in test scores between biology students who had started their course with either Mendel or molecular genetics.2 Mendelian genetics lent no special insight, nor did it prove itself a “softer” subject. At the secondary school level, everything from card games to gummy bears has been deployed to assist students in tracking the movement of genes through the generations.3The level of difficulty involved in grasping Mendel's laws has important historical ramifications. Staffan Müller-Wille and Giuditta Parolini have recently suggested that the spread of Mendelism among biologists was only thanks to a “computational protocol” that allowed early geneticists to reconstruct the logic behind Mendelian experiments.4 The uptake of Mendelian principles among farmers and breeders is more difficult to trace.5 A growing body of literature does point to several reasons why Mendel was popular among agriculturalists in the United States. Genetics fits with a preexisting trend toward the “rationalization” of American agriculture. Mendelism made crops uniform and predictable, opening the door to industrialized agriculture and intellectual property laws.6 In other national contexts, however, Mendelian genetics faced a turbulent reception. In France, breeders found that Mendelian principles did not always apply to cereal breeding.7 In Britain, too, famed plant breeder Rowland Biffen struggled to apply the new breeding method to the creation of disease-resistant wheat.8Given the difficulties experienced by students, alongside ongoing historiographical debates, I naturally approached the challenge of teaching a class on the modern history of Mendelian genetics with a degree of trepidation. The class in question formed part of a weeklong summer school at the University of Cambridge, titled “The Science and Politics of Food in Human History.” The summer school was hosted by the Centre for Global Knowledge Studies at the Centre for Research in the Arts, Social Sciences and Humanities (CRASSH). Students at the point of transition from undergraduate to postgraduate studies were recruited under the University of Cambridge's “Widening Participation” guidelines. There was no requirement for qualifications or background knowledge of either biology or history.By the third day of the summer school, students had encountered a range of disciplines and classroom styles. Dr. Marie-Françoise Besnier harnessed “The Irrigation Game; or, How to Lead Your Village through the Sumerian Agricultural Year,” her way of introducing participants to the complexities of Mesopotamian agriculture. Professor Martin Jones, accompanied by crop plant specimens, explored the origins of the “Big 3” (wheat, rice, and maize), while Dr. Inanna Hamati-Ataya used maps to trace the Neolithic movement of crop plants. For students in the summer school, novel teaching materials and interactive classes were already the norm by the time of the class on “The Modern British History of Mendelian Plant Genetics.”Inspired by an alternative approach to the teaching of genetics at the University of Leeds, I took the opportunity to engage in a pedagogical experiment.9 The class began with some historical background to the problems of breeding and inheritance prior to and during the nineteenth century. This background included the classic example of how to breed faster racehorses, an argument that attracted numerous theories for over a century.10 We discussed efforts to produce stable plant hybrids, a problem in which Mendel himself—trained in horticulture and a member of the Natural Science Section of the Agricultural Society in Brno—was engaged.11The bulk of the class was devoted to a practical exercise on Mendelian genetics. Like many traditional classes on Mendel, this exercise harnessed the Punnett square.12 Yet it made no mention of genetic terminology, instead referring purely to practical characteristics in plants and animals: short or long horns in cattle, the length of wheat, and coarse or luxuriant fleeces in sheep. Students were asked to predict the outcome of these different varietal crosses down the generations. Take the classic example of green and yellow peas, where yellow (Y) is the dominant trait and green (g) the recessive. An initial cross (the F1 generation) will give you yellow peas due to yellow being the dominant trait. However, a second generation (F2) will give you the classic Mendelian ratio of three yellow peas (YY or Yg) to one green pea (gg). Interesting, but you still have the same yellow or green peas you began with. After working through a few of these examples, the students turned to Punnett squares with two traits in play. Again, take a classic example of crossing green and round (gR) peas with yellow and wrinkled (Yw) peas. A first cross gives us the dominant yellow and round (YR) peas. Yet in our second (F2) generation we find a whole mix of peas, including one hybrid (gw) that we did not have with the parent varieties or the first (F1) generation.The aim of this exercise was to see whether the students could explore how novel hybrids could be produced through crosses and the implications of this for agriculture. Students worked with a similar series of Punnett squares to produce new varieties of woolly and short-horned cattle and short-stemmed, disease-resistant wheat. For a few students, the potential of Mendelian genetics suddenly became tangible: a moment of excitement that plant and animal breeding could be directed and controlled. Yet for other students, this practical approach to Mendel made no difference to their understanding. There was almost unanimous agreement, however, that a breeding program based on Mendelian genetics would be time-consuming and costly to enact.13 This outcome was not altogether unexpected. Similar efforts to contextualize Mendelian genetics as a historical breeding problem or to study it through real-life examples have similarly produced mixed results.14The split reaction of contemporary students to Mendelism perhaps indicates why its reception in agriculture was so divided. For some, Mendelian genetics produces a kind of “breakthrough” moment, accompanied by genuine excitement. For others, this never arises. I was only able to arrive at the former through some effort. It is also important to note that the early twentieth-century agriculturalists who encountered Mendelism would already possess numerous ideas on how breeding should be done, including selection, inbreeding, and crosses. When Charles Darwin approached pigeon breeders to construct his nineteenth-century analogy between artificial and natural selection, he greatly simplified his account of their practices to form his argument.15 An alternative (and longer-term) approach to teaching Mendelism and agriculture would involve immersing students in the specific challenges encountered by breeders at different points in time. From this perspective, Mendelism was not an unforeseen and complex new system to learn but was instead a relatively simple argument which removed some of “the baffling clutter” surrounding heredity.16