Why the Bateson–Weldon Debate over Mendelism Matters, Then and Now
ISHPSSB Annual Meeting, Toronto, 9-15 July 2023
The dust-up over Mendelism in the early twentieth century between William Bateson at Cambridge and his former friend turned critic W. F. R. Weldon at Oxford has absorbed far more historiographic attention than its historical or scientific interest warrants. Once we expand focus even a little bit beyond those two men, we see that their debate was an inconsequential storm in an English teacup. No one else saw conflict, let alone important conflict, between the “biometrical” perspective represented by Weldon and the Mendelian perspective represented by Bateson. Even Bateson and Weldon in their respective scientific visions made room for the patterns and methods so prominent for the other. Expand focus even further, and we see that the major “take home” about the study of inheritance in the early twentieth century was its enormous heterogeneity, with Mendelism, and the various means of accommodating it, just one part of a large, complex, diversely plural – and international – scene. Surely the time has come to consign the Bateson–Weldon debate, ending with Weldon’s death in 1906, to the minor position it actually occupied.
In my talk – and more extensively in my new book Disputed Inheritance: The Battle over Mendel and the Future of Biology – I aim to show why the above, for all that it gets right (and it gets a lot right), should strike us as not just unsatisfactory but misleading. Much depends, I will suggest, on what we take ourselves to be studying when we study the history of genetics. If it’s just the reflective thoughts of elite scientists then, undoubtedly, there’s little reason to consider Weldon’s disagreements with Bateson and his allies as any more worthy of attention than the positions of the many other scientists and scientific collectives active at the time, with their diverse views and debates. But if instead we take the history of genetics to encompass not just elite discussion but the public life of genetics – genetics as it got taught in schools, read about in popular books and magazines and newspapers, argued over in courtrooms deciding about eugenic sterilization – then what’s truly striking and needs explaining, I will suggest, is how wide and deep elementary Mendelism has gone in global culture, in ways that are not straightforwardly good or inevitable, and that should prompt us to ask about alternative possibilities, for the present as well as the past. Yes, nobody else was anything like as bothered about Mendelism as Weldon was; but that is precisely what made him important in his own day, and what makes the recovery of his perspective on Mendelism – which has become so hard to “unthink” – important in our day.
A Look Back at ‘Biometrician Versus Mendelian: A Controversy and its Explanation’ (1974)
Departmental seminar, Department of History and Philosophy of Science, University of Cambridge, 27 April 2023.
Over the past fifty years, a major stimulus for history and philosophy of science has been contact with the sociological study of scientific knowledge. In this seminar I want to outline and reflect on the achievement of a sociological paper dating from the start of this period: “Biometrician Versus Mendelian: A Controversy and its Explanation,” by Donald MacKenzie and Barry Barnes. When the paper was completed in September 1974, MacKenzie was a PhD student in the Science Studies Unit in Edinburgh, where Barnes was his supervisor. Remarkably, this classic case study in “Edinburgh School” sociology of scientific knowledge was never published in its original English-language form. One aim of this seminar is simply to make the paper more widely available. Another is to give seminar participants the opportunity—Zoom permitting—to hear about it from Donald MacKenzie directly. In my contribution I’ll suggest that the paper continues to repay scholarly attention, not because its main claims are correct (I’ll give my reasons for thinking they aren’t), but because it permanently raised the bar for historians concerned to address the explanatory challenges posed by the debate over Mendelism, and perhaps even for scientific controversies generally.
A Defense of Minimal-Rewrite Counterfactuals in the History of Science
Keynote address, 9th Integrated History and Philosophy of Science Conference, University of South Carolina, 16‒18 March 2023.
Should we care whether alternative-science counterfactuals are historically plausible? A concern with “minimal rewrite” plausibility – expressed, for example, by sticking to consideration of alternatives that were actually contemplated at some juncture point in the scientific past – has been criticized as overly restrictive, needlessly constraining historians from realizing the most radical potentialities of a counterfactual approach. While recognizing the value for certain purposes of a maximalist approach to history-of-science counterfactuals, this talk defends the minimalist constraint, along three lines. The first explores a parallel with a recent defense from the philosopher of biology Elliott Sober of evolutionary theory as preferable to Intelligent Design theory because of the former’s superior track record in priming new observations. The second illustrates the priming power of minimalist history-of-science counterfactuals with an example from my own recent research into an alternative history for the twentieth-century science of heredity. The third uses the case of curriculum reform now underway in genetics classrooms around the world to put pressure on the assumption that minimal-rewrite counterfactuals are by their nature minimally radical in their consequences.
Disputed Inheritance: The Battle over Mendel and the Future of Biology
Mendel Bicentenary seminar, Bristol University (in-person and online), 9 March 2023.
The celebrations of Gregor Mendel (1822-1884) and his legacies in this bicentennial year have reaffirmed his place in the biological pantheon. But there is room for disagreement about how uniformly positive those legacies have been, and about whether Mendelian patterns and concepts were bound to become as central as they in fact became. In this talk I want to explore the case for thinking that, had an early twentieth-century debate over incipient “Mendelism” gone differently, scientific knowledge of heredity today would be just as powerful, and yet the central, organizing, starting-point idea of that science would be expressed not in a Punnett square (in which characters are categorical and depend on nothing but gene variants) but in a GxE diagram (in which the conditioning role of context on variable gene expression is unmissable). Drawing on recent archival research as well as on classroom experimentation, I will suggest that awareness of this alternative or “counterfactual” possibility for genetics past, with its greater emphases on phenotypic variability and multifactorial causation, can valuably help us think afresh about present-day options, especially in the teaching of genetics.
Why Mendel Matters
Public lecture, Lichfield Science and Engineering Society, at the Garrick Theatre Lichfield, 1 December 2022, 8 pm
Even in 2022, two hundred years after the birth of Gregor Mendel (1822-1884), students learning about inheritance start with Mendel’s famous experiments crossing varieties of the garden pea. But should they? Does it really make sense, in the age of genomics and epigenetics, to teach students to think of Mendel’s peas as exemplary of how inheritance works? This talk will suggest that an old debate about Mendel’s experiments casts new light on Mendel’s legacies, including his legacies for the classroom.
The Gregor Johann of History and the Mendel of Faith: Reflections for a Bicentennial
KLI Mendel Symposium: Mendel’s Legacy in Science and Society (in-person and online) 13-14 October 2022
The Role of the Cold War in Transforming a Statistical Puzzle about Mendel’s Pea Data into a Scientific Scandal
Mendel 200 Conference, Brno, 20‒23 July 2022
The history of interest in the question of whether, statistically considered, Mendel’s data from his hybrid-pea experiments are “too good to be true” has an intriguing structure. When the British mathematician and evolutionary theorist Ronald Fisher published his classic analysis in 1936, knowledge that Mendel’s data conformed improbably closely to the predictions of his theory was long familiar among specialists. Furthermore, for decades after Fisher published, the issue largely remained a matter for specialists to puzzle over. There was no “Mendel-Fisher controversy,” and no public hand-wringing about Mendel’s truthfulness. What turned this long-running minor concern into a major scientific scandal, I will suggest, was a particular 1960s/70s conjunction of historical developments, notably (i) the centennial celebrations of Mendel’s 1865 lectures and 1866 paper; (ii) the changing cultural dynamics of the Cold War, on both sides of the Iron Curtain; and (iii) a new public mistrustfulness towards science, and scientists, in the West. This talk draws on research set out in my paper “Mendel the Fraud? A Social History Truth in Genetics,” Studies in History and Philosophy of Science 93 (2022): 39-46.
“As Man Advances in Civilisation…”: Darwin on the Expanding Circle of Moral Regard, From His Day to Ours
Descent of Man conference in honour of Jean Gayon, Institut d’Etudes Avancées de Paris, 5‒6 July 2022
In the third chapter of Charles Darwin’s Descent of Man (1871), on the evolutionary origins of what Darwin called “the moral sense,” he wrote:
As man advances in civilisation, and small tribes are united into large communities, the simplest reason would tell each individual that he ought to extend his social instincts and sympathies to all the members of the same nation, though personally unknown to him. This point once being reached, there is only an artificial barrier to prevent his sympathies extending to the men of all nations and races. If, indeed, such men are separated from him by great differences in appearance or habits, experience unfortunately shews us how long it is before we look at them as our fellow-creatures. Sympathy beyond the confines of man, that is humanity to the lower animals, seems to be one the latest moral acquisitions.
My paper will track the fortunes of this passage across the last century and a half of public Darwinism. I’ll begin by looking at the role of the passage in Darwin’s book, as well as in his thought on humans and their evolution generally. From there I’ll look in particular at the passage’s subsequent appearance in two striking places: first, as the sole quotation from a scientific author in the 1950 UNESCO Statement on the Race Question (about which, of course, Jean Gayon wrote an important paper); and as the epigraph to the concluding chapter of the evolutionary psychologist Steven Pinker’s 2011 bestseller The Better Angels of Our Nature: A History of Violence and Humanity. Against any impression that this lineage might suggest of a consensus enduring from Darwin’s day to ours about the interactions of biology, reason and morality, I’ll argue on the contrary that hidden beneath the surface continuity is a remarkable discontinuity, located in the years around 1900. I’ll also argue that once we recognize this discontinuity, we can better understand how natural selection came to be used in the twentieth century both to underwrite the concept of human rights biologically and to undermine that concept.
Vervetese and its Contexts
The Riddle of the Organism conference, Ruhr‒Universität Bochum, 24‒25 March 2022
If any science has authority over animal agency, it is cognitive ethology. Promoted by Donald Griffin in the mid-1970s, cognitive ethology only got started in a serious way with the famous vervet alarm call study of Robert Seyfarth, Dorothy Cheney and Peter Marler, published in 1980. By using experimental playback at the Amboseli National Park in Kenya, Seyfarth et al. claimed to establish that the alarm calls of the vervets were “rudimentarily semantic,” in that they conveyed information not just about the emotional state of the caller but about the nature of the environmental threat – specifically, whether a leopard or an eagle or a python was present. This paper will explore interconnected philosophical and historical issues to do with a pivotal but little remarked upon feature of this study: its operationalizing of an intuition about how calls should function independently from contexts if the calls are to count, even remotely, as word-like. Previous historical research has shown that the test operationalizing that intuition in the published work was different from — and arguably less demanding than — a test used at an earlier, less successful phase of the research. The later, published test went on to enjoy a largely criticism-free life for over a quarter of a century. But then, around 2009, debate suddenly opened up, and has remained on the boil. What concerns have been raised? By whom? And why at this time? In answering these questions, the paper will explore not just context within the debate but the contexts of the debate itself, emphasizing three in particular: the maturing of the field; the public scandal over the work of Seyfarth and Cheney’s most high-profile protégé, Marc Hauser; and the publication of the historical research mentioned above. The paper will end with some thoughts on whether an energizing context for the original study — the ape language-teaching experiments run by comparative psychologists — may have set cognitive ethology on the path of becoming a “protest science,” to the chagrin of later practitioners. Their dissatisfaction in turn bears reflection, the paper will suggest in conclusion, for anyone excited by the prospects of next-wave animal agency science.
From Cleopatra’s Nose to Darwin’s Nose: J. B. Bury on History, Science and Contingency
SPHERE laboratory, Université de Paris, 15 December 2021.
“Le nez de Cleopatra: s’il eût été plus court, toute la face de la terre aurait changé.” Pascal’s line, from his Pensées, centuries later went on to serve as the title of a famous 1916 essay by the Cambridge historian John Bagnell Bury (1861-1917) highlighting the role of contingency in history. What, exactly, was Bury arguing for, in that essay as well as in an earlier companion piece, “Darwinism in History” (1909)? Why did the theme of contingency in historical science and scientific history come to preoccupy him as it did in these years? And what, now, should we make of one of his most startling claims in his 1916 essay: that, over the longue durée, contingency has become less important – and that its importance will continue to diminish? In this talk I’ll offer some preliminary answers to these questions.
Napp, Mendel and the Problem of Heredity
Mendel Days 2021, Mendel Museum, Brno, 3 November 2021 (online).
Here I present some reflections on how, and how not, to think about what the lively Abbott Cyrill Napp did for Gregor Mendel, arguing against the common idea that Napp set Mendel the task of figuring out how heredity works.
Why Plausibility Matters for Alternative-Science Counterfactuals
Should We Choose One Unique Scientific Theory? workshop, Nancy, 22 October 2021.
Should we care whether alternative-science counterfactuals are historically plausible? A concern with ‘minimal rewrite’ plausibility – expressed, for example, by sticking to consideration of alternatives that were actually contemplated at some juncture point in the scientific past – has been criticized as overly restrictive, needlessly constraining historians from realizing the most radical potentialities of a counterfactual approach. While recognizing the value for certain purposes of a maximalist approach to history-of-science counterfactuals, this talk defends the minimalist constraint, along three lines. The first explores a parallel with a recent defense from the philosopher of biology Elliott Sober of evolutionary theory as preferable to Intelligent Design theory because of the former’s superior track record in priming new observations. The second illustrates the priming power of minimalist history-of-science counterfactuals with an example from my own recent research into an alternative history for the twentieth-century science of heredity. The third uses the case of curriculum reform now underway in genetics classrooms around the world to put pressure on the assumption that minimal-rewrite counterfactuals are by their nature minimally radical in their consequences.
Genetics for the Real World
Research Seminar, Biological Sciences Curriculum Study (online), 29 September 2021.
The traditional, start-with-Mendel introductory curriculum in genetics is, at its best, outstanding in helping students to learn to “think like a geneticist.” But is that an appropriate goal for genetics education in the 21st century? In this talk, I want to make the case for a genetics curriculum which aims less at creating geneticists than at improving students’ ability to cope well with the genetic information which increasingly surrounds them. I will dwell in particular on one attempt to “de-Mendelize” the genetics curriculum, putting much greater emphasis than is traditional on phenotypic variability and on the complex gene-gene and gene-environment causal interactions which bring about that variability. I will also discuss a BSCS Science Learning-Cornell project now underway to assess the impact on students of these alternative emphases.
Darwin’s Analogical Reasoning
Keynote address, Analogical Reasoning in Philosophy and Science workshop, Canterbury Cathedral Lodge, 28 May 2021; reprised in part at a session at the virtual ISHPSSB meeting, July 2021, and again at the Leeds Integrated HPS meeting, June 2022.
In the year marking the 150th anniversary of Darwin’s Descent of Man, it’s fitting to note that the extended analogy he draws in that book between languages and species (and which I wrote about at length in a 2008 paper) is an instance not of analogical argument as such, but of one kind of analogical argument, analogy as similitude. In a new book coming out this year with my Leeds colleagues Jonathan Hodge and Roger White, Darwin’s Argument by Analogy: From Artificial to Natural Selection, we recover a second, much older and yet, within the history and philosophy of science, largely forgotten tradition of analogical argumentation, analogy as proportion. Where differences between the things analogized tend to weaken similitude arguments, those differences are constitutive of proportional arguments, explaining why one cause has effects which are the same in kind but different in degree from the analogized cause. In our view, when, in the Origin of Species, Darwin anchored his case for the power of natural selection to produce new species on an analogy with artificial selection on the farm – his most famous analogy, within one of the most consequential chains of reasoning in the whole history of science – he did so on the expectation that his readers would recognize the analogy as a proportion argument. With the analogy thus understood, Darwin’s associated metaphors (“Nature selects”) become both more intelligible and more admirable.
Challenges to Data Linkage in Plants: Two Parables from the Pea
Towards Responsible Data Linkage online workshop, University of Exeter, 12 March 2021.
This talk draws upon the history of scientific studies of inheritance in Mendel’s best remembered model organism, the garden pea, as a source of two parables – one pessimistic, the other optimistic – on the challenges of data linkage in plants. The moral of the pessimistic parable, from the era of the biometrician-Mendelian controversy, is that the problem of theory-ladenness in data sets can be a major stumbling block to making new uses of old data. The moral of the optimistic parable, from the long-run history of studies at the John Innes Centre of aberrant or “rogue” pea varieties, is that an excellent guarantor of the continued value of old data sets is the preservation of the relevant physical materials – in the first instance, the plant seeds.
The Jewish Disease? Tay-Sachs in Science, History and Pedagogy
Jewish Historical Society of England (Leeds branch), online talk, 7 December 2020.
Here I set out some preliminary reflections on a textbook Mendelian disease now commonly thought of as a distinctively Jewish problem. It turns out that, like pretty much all Mendelian (i.e. “single-gene”) conditions, Tay-Sachs can be highly variable in its expression. Nor is it an exclusively Jewish problem. Taking those complications seriously in turn raises questions about a familiar Darwinian explanation of the spread of Tay-Sachs: that, in the tubercular conditions of the European ghettos where many Jews lived for centuries, individuals who were heterozygous for the condition (that is, who inherited one normal allele and one mutant allele) were favoured. At the same time, recent classroom studies suggest that, when we teach students that Tay-Sachs, sickle-cell anaemia etc. are racially distinctive Mendelian conditions, we lose more than we win.
How Can We Know What Might Have Been in the Scientific Past? Reflections on the Debate over Mendelism
Une science radicalement différente est-elle plausible? Université de Lorraine, Nancy, 18-19 December 2019.
We make judgments all the time about all kinds of claims about the might-have-been or counterfactual past. At least some of the time, those judgments take into account evidence from the actual course of history. Concentrating on claims about the counterfactual scientific past, this talk will consider the kinds of evidence that can bear in deciding questions about whether a given scientific achievement was inevitable, i.e independent of its particular history, or whether, had that history gone differently, science might have gone differently too. The kinds of evidence to be considered are: (i) evidence from histories converging on the scientific achievement in question; (ii) evidence from histories diverging from that achievement; (iii) evidence of alternatives under contempation at the time; and (iv) evidence from attempts to develop those alternatives in the present. Throughout I’ll draw on examples from my own studies of the post-1900 debate over Mendel, including, under (iv), an experiment assessing the effects of teaching genetics from a Mendelian or a “Weldonian” starting point. I’ll suggest that the availability of (iv) potentially puts counterfactual histories of *science* on a more secure epistemic footing than other kinds of counterfactual history. And I’ll stress that, beyond (i)-(iv), historians of science pursuing a counterfactual thesis can avail themselves of all the evidence relating to what was dependent on what in the post-achievement history of science.
Mendel the Fraud? A Social History of Truth in Genetics
New Directions in the Historiography of Genetics workshop, Cohn Institute, Tel Aviv University, 18-19 November 2019.
Abstract: Two things about Gregor Mendel are common knowledge: first, that he was the “monk in the garden” whose experiments with peas in mid-nineteenth-century Moravia became the starting point for genetics; second, that, despite that exalted status, there is something fishy, maybe even fraudulent, about the data that Mendel reported. This talk will explore the cultural politics of this accusation of fraudulence against Mendel. Although the notion that Mendel’s numbers were, in statistical terms, too good to be true was well understood almost immediately after the famous “rediscovery” of his work in 1900, the problem became widely discussed and agonized over only from the 1960s, for reasons having as much to do with Cold War geopolitics as with traditional concerns about the objectivity of science. Appreciating the Cold War origins of the problem as we have inherited it can, I will suggest, be a helpful step towards shifting the discussion in more productive directions, scientific as well as historiographic.
The Role of NIAB in the Success of Mendelism
NIAB at 100: Change and Continuity in Agricultural Botany and its Institutions 1919‒2019, Cambridge, 24 October 2019.
The LPLS and its Museum in Historical Perspective: Some Highlights from Recent Research
With Jonathan Topham. Leeds Philosophical and Literary Society Bicentennial Conference, Leeds, 19 October 2019.
Abstract for my part: Charles Darwin seems never to have doubted that the different human races originated from a common ancestral stock. But he was remarkably open-minded and even-handed about whether the races might nevertheless be so different from each other as to rank as distinct species, and not merely as varieties of just one species. For decades, from Darwin’s time on the Beagle voyage through to the publication of the Descent of Man, he used an apparent association between the different human races and distinctive species of lice as material for thinking through the species/varieties question. Throughout these investigations he corresponded with Britain’s leading expert in the natural history of lice, Henry Denny, curator of the scientific collections of the Leeds Philosophical and Literary Society. Drawing on a forthcomng paper with Mark Steadman (“Of Lice and Men,” BJHS Themes, 2021), this talk reconstructs the long run of Darwin’s inquiry and interactions on race, lice, and evolutionary history.
Disputed Inheritance: The Battle over Mendel and the Future of Biology
Institute for Basic Research into Developmental Disabilities, Staten Island, NY, 5 September 2019.
How Changes in Agricultural Education Can Help Promote Sustainable Agriculture in India
Sustainable Seed Innovations 2.0 conference, Art of Living campus, Bangalore, 30 July 2019.
Abstract: This conference will be launching a Position Paper outlining a three-pronged approach to promoting a more sustainable future for Indian agriculture, stressing the revival of Traditional Ecological Knowledge systems (Prong 1), the updating of agricultural education to promote sustainability (Prong 2), and the use of new smart technologies to incentivize and monetize farmer-level innovation with indigenous seeds in an ecologically and socially sustainable manner (Prong 3). In addition to introducing the background to the Sustainable Seed Innovations Project, I’ll be presenting the Prong 2 material, which is currently available in draft form on the Spicy IP website. It addresses the need to redesign elements of agricultural training to ensure a better fit with the goal of greater sustainability, looking in particular at how my historical research into the organization of knowledge in two areas — Mendelian genetics and intellectual property — has opened up new options worth considering.
Classroom Mendelism and its Role in Sustainable Agriculture
John Innes Centre, Norwich, 24 July 2019.
Abstract: In this talk I’ll be examining links between (i) what we might call the “Green Revolution” high-yield agricultural ideal, emphasizing the use of genetically standardized seeds along with the fertilizers, pesticides, irrigation systems etc. with which farmers give those seeds the standardized environments they need; and (ii) what we might call the “start with Mendel” pedagogic ideal in genetics education, emphasizing the use of elementary Mendelian patterns and explanations as foundational for understanding how heredity works, viz. as, in the first instance, down to which “genes for” traits are present and in what forms. Drawing on some recent collaborative work with partners in India, I’ll explore the possibility that, in India and perhaps elsewhere, changing from a high-yield to a high-value agricultural system, where the emphasis is instead on indigenous varieties sustainably grown in the regions to which they’re adapted, in ways that are good for biodiversity as well as for farmer dignity and income, community building etc., partly depends on giving farmers a scientific education in which gene-environmental interactions are seen not as an extra complication or a nuisance but as fundamental to how heredity works.
Degeneration and Victorian Cultural History: The Surprising Challenge from the New Historiography of Quantitative Genetics
ISHPSSB conference, Oslo, 7‒12 July 2019.
Abstract: A commonplace about nineteenth-century cultural history, in Europe and beyond, is that it was an age characterized by increasing anxiety about biological degeneration. Like any such generalization, this one has its uses, but it also has its limits. In this talk I want to consider how differently the topic of degeneration looks when it’s no longer viewed as the cultural equivalent of an irresistible force, seeping miasma, doomily enervating mood music etc. The inspiration for this exercise is Ted Porter’s Genetics in the Madhouse: The Unknown History of Human Heredity (Princeton, 2018), where, among many other things, Porter shows that the French asylum doctor B. A. Morel’s claims about degeneration as the universal fate of the human species were subjected to severe criticism by his professional peers, who were able to mount their arguments thanks to painstainkingly accumulated quantitative data on the inheritance of insanity. Porter’s work illustrates how the new historiography of quantitative genetics, for all its specialist appeal, can cast light on subjects of much wider historical interest.
Against Monocultures, Intellectual and Agricultural
Integrated HPS workshop, University of Exeter, 20‒21 June 2019
‘If Only Darwin Had Read Mendel…’
International Mendel’s Day conference, Royal Institution, London, 8 March 2019. Afterwards I recorded this podcast interview about the talk with Kat Arney. Here’s Kat’s intro:
“While we know that Mendel read Darwin, as evidenced by his pencil-marked copy of Origin of Species at the Abbey, did Darwin read Mendel? I was particularly fascinated to hear from one of the Mendel Day speakers, Professor Greg Radick from the University of Leeds – a leading expert in the history of genetics – who’s been speculating on this scenario.
So, I just had to drag him out of the drinks reception at the end of the day to chat about Darwin’s ideas about heredity, and to bust some myths about the intellectual relationship between these two men.
Greg: Well, they had no interaction as people or as thinkers. Mendel read Darwin, that we know for sure. Mendel’s copies of the Origin of Species and another book of Darwin’s exist, they’ve been studied….“
There was No Such Thing as the Mendelian Gene and this is a Talk about it
How Scientific Objects End workshop, University of Cambridge, 3 December 2018.
Evelyn Fox Keller’s The Century of the Gene (2000) remains the most famous obituary of the concept born out of enthusiasm for Mendel’s 1866 paper. If we define Mendelian genes as those dominant-or-recessive entities whose pairings do the explanatory work in elementary genetics (in answering, e.g., the question of why blue-eyed parents have only blue-eyed children), then, on Keller’s account, the Mendelian gene concept should have expired long ago, so badly does it fit the accumulated facts. But what kind of a life did that concept ever really have, anyway? Haven’t thoughtful biologists always regarded it as an oversimplification? Indeed, from early days, Mendelians allowed for all kinds of complexity. They nevertheless relentlessly showcased the power of Mendelian explanations to cut through complexity and expose underlying simplicity. In the spirit of Keller’s Making Sense of Life (2002), this paper documents this “ambi-valence” in order to suggest how crucial it has been in making the Mendelian gene concept — and the determinism it underwrites — so long-lived.