Ernst Mayr's Interactions with JBS Haldane

HPLS DOI 10.1007/s40656-016-0098-x

NOTES AND COMMENTS

Ernst Mayr’s interactions with J. B. S. Haldane

1 2,3 Veena Rao • Vidyanand Nanjundiah

Received: 30 October 2015 / Accepted: 8 February 2016 Ó Springer International Publishing AG 2016

Abstract Ernst Mayr and J. B. S. Haldane, major contributors to the ‘modern synthesis’ in evolutionary theory, set an example of how scientiﬁc disagreements need not come in the way of friendship. After getting acquainted, they kept discussing issues related to evolution until just before Haldane’s death in 1964. Their dissimilar backgrounds meant that they adopted different approaches. A major disagreement emerged regarding the right way to look at the role of genes in evolution. Mayr felt that the elementary models of population genetics were oversimpliﬁcations and therefore inadequate for representing evolutionary processes, though he was not consistent in his attitude. Haldane, on the other hand, maintained that the mathematical treatment of simple models had an important role to play. The Mayr-Haldane interactions illustrate divergent viewpoints concerning the utility of mathematics in biology.

Keywords Population genetics Á Beanbag dispute Á Evolution Á Mathematical models

& Veena Rao [email protected] Vidyanand Nanjundiah [email protected]

1 National Institute of Advanced Studies, Bangalore 560012, India 2 Stellenbosch Institute for Advanced Study (STIAS), Wallenberg Research Centre at Stellenbosch University, Marais Street, Stellenbosch 7600, South Africa 3 Centre for Human Genetics, Electronic City (Phase I), Bangalore 560100, India 123 V. Rao, V. Nanjundiah

1 Introduction

Population genetics is a mathematical approach that aims at explaining biological evolution in terms of how evolutionary forces affect the distribution of genes and genotypes in populations. Natural selection, drift, some other evolutionary process, or combination of processes, provide its theoretical underpinnings. How gene and genotype frequencies vary in space (within populations) and time (over generations) has been a major concern of population genetics.1 The most elementary formulation, which continues to be taught to this day, involves a single locus, (usually) two alleles at each locus, a genetic system that operates according to Mendelian principles, a deterministic genotype-phenotype relationship and a fixed fitness associated with each phenotype. If allelic combinations at different loci influence the phenotype, and therefore fitness, but do so independently of one another, it is mathematically trivial to extend the one-locus two-allele formulation to several loci and two or more alleles at each locus.2 Simple as such models are, they have provided useful insights into several phenomena of evolutionary interest.3 Or have they? Among others, Ernst Mayr, one of the contributors to the Evolutionary Synthesis, famously thought not.4 In his view the models were not just simple, they were simplistic. He used the adjective ‘beanbag’ to lampoon models of Mendelian population genetics in which each gene locus was considered separately and independently: ‘The Mendelian was apt to compare the genetic contents of a population to a bag full of colored beans’.5 Mayr’s derisory characterisation was vigorously rebutted by his friend J. B. S. Haldane, a fellow contributor to the

1 See for example the standard texts by Li (1955) or Futuyma (2013). 2 Trivial in principle, that is. In practice, the combinatorial complexity increases rapidly with the number of loci; and, once recombination is considered, it becomes increasingly difficult to arrive at analytical solutions. 3 The classical books by Fisher (1930/1958/1999) and Haldane (1932/1990) are full of examples. Among them, one might cite the results that in the absence of natural selection, variation would be lost very slowly in large populations and relatively rapidly in small populations, that recurrent mutation can allow genes with deleterious effects to persist in stable equilibria and that ‘‘a selective advantage of the heterozygote over both homozygotes will preserve both of a pair of allelomorphs indefinitely’’ (Haldane 1953). Haldane (1953) goes on to say: ‘‘Such ideas as these pass rapidly from being mathematical theorems to being common sense. Other ideas with a superficial appeal to common sense, for example that dominants must oust recessives, appear to require mathematical disproof to prevent their spread’’, the last being a comment on what led to Hardy’s formulation of the celebrated Hardy–Weinberg principle (see Crow 1999). 4 Nor—eventually—did W. H. Provine, historian of population genetics. In contrast to the favourable stand he had taken previously, his opinion as expressed in the 2001 re-issue of The Origins of Theoretical Population Genetics was ‘‘Now I see these theoretical models of the early 1930s, still widely used today, as an impediment to understanding evolutionary biology…’’ (Provine 1971/2001). Regarding ‘‘Evolu- tionary—or ‘‘Modern’’—Synthesis’’, see Provine (1980). The appropriateness of the term, and whether a new synthesis is necessary, or even under way today, has been debated. 5 Mayr (1963, p. 263). The implied negative assessment was leavened with occasional positive statements. Earlier he had granted that beanbag genetics had made useful contributions, had been a ‘‘necessary step in the development of our thinking’’ and had ‘‘restored the prestige of natural selection’’ (Mayr 1959). But on the whole he seems to have thought that its contribution to evolutionary theory was questionable. 123 Ernst Mayr’s interactions with J. B. S. Haldane

Synthesis, in a celebrated paper that he wrote just before he died.6 The beanbag genetics dispute has been discussed by several authors7; its crux had to do with whether elementary population genetics provided interesting insights into understanding how evolution worked. Most recently, as part of a commentary in this journal dealing with Mayr’s recollections of his encounters with Haldane, Sarkar (2013; henceforth ‘‘SS’’) raises doubts regarding some statements made by us in the course of a discussion of the beanbag genetics dispute and its ramiﬁcations (Rao and Nanjundiah 2010/2011; henceforth ‘‘VR/VN’’). The doubts are sought to be supported by the inclusion in SS of the text of a typed manuscript that contains Mayr’s recollections of Haldane. The manuscript is stated to have been given by Mayr to Sarkar in 1992, 28 years after Haldane’s death.8 The extensive Haldane-Mayr exchanges constitute important material for students of the Evolutionary Synthesis. The present note extends what is contained in VR/VN regarding their interactions and reiterates the point that Mayr’s stance was inconsistent and at times unclear. We begin by addressing the three issues ﬂagged in SS as important (p. 272 of SS). In order, they touch on (1) a mix-up involving the concept of ‘cost of natural selection’ (and ‘genetic load’), (2) the year of Fisher’s death and (3) a misattribution.

(1) The alleged mix-up appears on page 249 of VR/VN. It goes ‘‘Haldane had advanced the notion that there would be a ‘cost’ of natural selection, also referred to as a ‘genetic load’ (H. J. Muller developed the concept independently).’’, and refers to Haldane’s 1957 paper (Haldane 1957). VR/ VN are said to have confused the substitutional load with the mutational load, and not to have noted either Haldane’s original formulation of the mutational load argument in 1937 or Muller’s independent development of it in 1950. Haldane (1957) does deal with the substitutional load and the statement pertaining to his and Muller’s formulations of the mutational load concept is valid. But the confusion is apparent, not real. The intention in VR/VN was neither to trace the history of the term ‘genetic load’ nor to distinguish between mutational and substitutional loads.9 Rather it was to draw attention, solely within the context, to the nature of the objection raised by Mayr to Haldane’s application of the concept of genetic (substitutional) load; an objection that, to be sure, was made with reference to Haldane’s 1957 paper. We were implicitly pointing out that irrespective of the source of the ‘load’, the essence of the argument remains unchanged. Namely, if each deleterious allele independently lowers the reproductive fitness of the individual that carries it, the difference in fitness between the maximally fit individual(s) and everyone else can cause the long-term geometric mean fitness of the population to become less than one. As a result, the population can go

6 Haldane (1964). 7 A list is provided in Rao and Nanjundiah (2010/2011), p. 236; also see Sarkar (2005, 2007, 2013). 8 According to SS ‘‘There is no explicit indication of why or when it was written’’. 9 For that matter, we have not tried to distinguish between them and other sources of genetic load either, e.g. the load due to recombination or segregation. 123 V. Rao, V. Nanjundiah

extinct—unless individuals of maximal fitness have a sufficiently large number of offspring; in the worst-case, an intolerably large number. That constitutes the ‘load’.10 Mayr asserted that Haldane had overestimated the load, because it could be significantly smaller, in fact easily tolerable, if alleles at different loci did not act independently.11 The reasoning is as valid for mutational load as it is for substitutional load. (2) SS states that the year of Fisher’s death is given wrongly in VR/VN. That was a regrettable lapse caused by overlooking a misprint, and we appreciate it being drawn to our attention.12 (3) SS refers to a misattribution in VR/VN. Sarkar (2005) contains the sentence ‘‘He [meaning Mayr] once told me that the only contribution that the mathematical theory had made was to show that evolution by natural selection could take place in the time available for it during the history of life on Earth.’’ Going by ‘‘once’’, VR/VN took it that the words following ‘‘told me that’’ were Mayr’s. We are informed in SS (p. 272) that they were based on Sarkar’s ‘‘reconstruction of several conversations with him [Mayr]’’, and are happy to accept them as such.

Coming back to the main purpose of the present note, we proceed to provide further documentary evidence pertaining to Haldane and Mayr’s interactions. It reinforces the conclusion that Mayr’s high regard for Haldane persisted in the face of their disagreement on the utility of population genetics. After that, we direct attention to puzzling aspects of Mayr’s negative assessment of elementary or ‘‘classical’’ population genetics. Both for its relevance to what we have to say and as a matter of historical interest, we reproduce in an Appendix photocopies of two letters (‘‘M1’’ and ‘‘M2’’), hitherto unpublished, addressed by Mayr to one of us and bearing on his feelings about Haldane.13 The ﬁrst is dated a few months short of his 100th birthday; the second is hand-written and dated three months after he had crossed 100.14 The rest of this note is organised in the form of answers to a set of questions.

10 Or, equivalently, ‘‘cost’’. Mayr (1963, p. 253) says that it can be thought of as the price to be paid for ‘‘prevent[ing] the depletion of genetic variability’’ and ‘‘thwart[ing] the homogenizing tendencies of natural selection’’. Slightly later he refers to ‘‘some six or seven kinds of genetic load’’. 11 Incidentally this illustrates Mayr’s essential reservation regarding ‘beanbag genetics’, namely that it glossed over the importance of interactions between alleles at different loci (also see later). VR/VN lists others who raised the same objection. 12 In VR/VN the year of R. A. Fisher’s death is stated incorrectly as 1960; it should have been 1962. The (wrong) date was used to infer that because that Fisher was no longer alive when Mayr’s 1963 book appeared, he could not have responded to it. Fortunately the inference stands. Had he chosen to do so, Fisher could have responded to the ‘beanbag’ criticisms that Mayr had made before 1962. It would be interesting to learn whether he knew of Mayr’s talk at the 1959 Cold Spring Harbor Symposium. 13 Ernst Mayr to Veena Rao, Museum of Comparative Zoology letterheads; M1 is typed and dated 18 March 2004 and M2 is handwritten with the date given as 28. Sept. 04. 14 According to the biographical memoir of Mayr by Walter J. Bock, he was born on 5 July 1904 and died on 3 February 2005 (see http://www.nasonline.org/publications/biographical-memoirs/memoir- pdfs). VR/VN (page 240) errs in giving the dates as 1905–2005. 123 Ernst Mayr’s interactions with J. B. S. Haldane

1.1 When did Haldane and Mayr meet?

1.1.1 The ﬁrst meeting

VR/VN (page 242) says ‘‘The two appear to have met for the first time in Princeton, New Jersey, in 1947 at an international conference held under the auspices of the US National Research Council at which Sewall Wright was also a participant.’’ SS contains a number of remarks about this. First, relying on the Mayr typescript that is reproduced there, SS states ‘‘Mayr’s account of meeting Haldane for the first time in 1953 contradicts the account given in Rao and Nanjundiah (2011, p. 242) which has them meeting in Princeton in 1947. Rao and Nanjundiah cite Mayr (1980) but no such claim is made in that piece. They also mistakenly seem to think that the Pavia Conference was in 1951, not 1953’’. SS goes on to ‘‘strongly suggest[.]’’, on the basis of the correspondence between Mayr and Haldane, ‘‘thatthey did meet for the first time in 1951, probably on 31 May, at Haldane’s laboratory at University College, London.’’ The main point is easily addressed. The proceedings of the 1947 Princeton Conference on Genetics, Palaeontology and Evolution15 make it amply clear that Haldane and Mayr both attended and both presented papers—and so did Sewall Wright, another of the founders of population genetics. If one prefers visual evidence, a group photograph is available.16 It may be, therefore, that when Mayr wrote ‘‘I did not become aware of Haldane’s work until about 1947’’ (Mayr 1980, page 421, as mentioned in VR/VN on page 242), he was alluding to their encounter at the Princeton Conference.17 Mayr’s letter to VR (Appendix, M1) says ‘‘I first met him in the 1940s and 50s at meetings in the United States, England and Italy’’. The simplest resolution of the conflicting dates of their first meeting is that Mayr’s memory played him false when he prepared the typescript shown in SS.

1.1.2 Subsequent meetings

As surmised in VR/VN, 1951 would appear to have been the year of their next, and therefore second, meeting.18 The evidence is indirect but strong. Mayr travelled to Pavia (among other places in Europe) in 1951 to give a course of lectures in Buzzati-Traverso’s department at the University. VR/VN reproduces extracts from a letter dated March 16, 1951 from Mayr to Haldane conﬁrming this.19 A letter from

15 Jepsen et al. (1949). 16 See Cain and Mayr (2004). 17 Except possibly in the case of Wright, Mayr’s acquaintance with the work of the population geneticists appears to have begun after they had begun to make substantial contributions. Prior to mentioning Haldane, he says (on the same page) ‘‘People have often asked me what impact Fisher, Haldane and Wright had on my thinking. My answer is quite embarrassing. I knew nothing of Fisher until I read Dobzhansky (1955), and even then I did not read Fisher’s book’’; and further, ‘‘at the time [the impression one gets is that he means in 1931 or 1932] I had not yet heard of Wright and genetic drift’’. 18 Letter from Mayr to Haldane dated 16 March 1951 (No. HUGFP 74.7, Box 8, F384; Pusey Library, Harvard University Archives, Cambridge, MA, USA), see p. 242, footnote 25 in Rao and Nanjundiah (2010/2011). 19 Ibid. 123 V. Rao, V. Nanjundiah

Haldane to Mayr, probably a reply sent later the same year,20 carries an invitation: ‘‘I hope you will spend at least a day here…we would like to have you very much if only for a few days’’. Mayr seems to have accepted the invitation, because on 26 September 1951 he writes to Haldane,21 ‘‘I am back in New York…Next time I shall certainly plan to stay in England longer. One of the men I met in your lab, Freeman, works on ﬂeas, if I remember correctly…’’. It would seem that besides staying with the Haldanes, Mayr visited Haldane’s laboratory (SS deduces that the date must have been May 31, 1951). In fact Haldane wrote back to Mayr on October 3, 1951 ‘‘We greatly enjoyed your visit’’.22 It is likely that the Haldane-Mayr meeting in 1951 was triggered by the news of Mayr’s impending visit to Pavia. As far as we are aware, there was no ‘‘Pavia Conference’’ in 1951 pertinent to the matter under discussion, nor, contrary to SS, does it say so in VR/VN.23 There was indeed a Pavia Symposium on ‘‘The Genetics of Population Structure’’ organised by Buzzati- Traverso in 1953, at which Mayr and Haldane met again.24 The Haldanes migrated to India in 1957. Mayr visited them in Calcutta in 1960 (possibly in February, as the Mayr typescript in SS indicates), not in 1959. The following pieces of evidence strengthen the conjecture. Mayr wrote to Haldane on April 13, 1959, saying that he was planning to go to Australia and was interested in visiting Haldane in Calcutta on his way back to the USA.25 In a letter of 30 December 195926 Haldane expresses his happiness at the news, says that February is a good month to visit Calcutta, and adds that he is busy drawing plans to visit Orissa along with the anthropologist Nirmal Kumar Bose.27 The letter from Mayr to VR dated 18 March 2004 (Appendix, M1) conﬁrms that the visit took place in 1960 when Mayr was on his way back from Australia.

20 Undated letter (inferred to be sent in summer 1951) from Haldane to Mayr (No. HUGFP 74.7, Box 9, F 406; Pusey Library, Harvard University Archives, Cambridge, MA, USA), see footnote 26 on p. 243 of Rao and Nanjundiah (2010/2011). 21 Letter from Mayr to Haldane dated 26 September 1951 (No. HUGFP, 74.7, Box 9, F 406; Pusey Library, Harvard University Archives, Cambridge, Mass, USA), see footnote 27 on p. 243 of Rao and Nanjundiah (2010/2011). 22 Letter from Haldane to Mayr dated October 3, 1951 (no. HUGFP 74.7, Box 9, F 406; Pusey Library, Harvard University Archives, Cambridge, Mass, USA). 23 Mayr had told Haldane that he was going to ‘‘lecture to Buzzati-Traverso’s department’’ in the University of Pavia (footnote 25 on p. 242 of Rao and Nanjundiah 2010/2011). 24 The proceedings were published in Buzzati-Traverso 1954. Nevertheless the 1953 Pavia Symposium is signiﬁcant as a forerunner of the Mayr-Haldane dispute on the usefulness of population genetics calculations based on Mendelian genes. See discussion on p. 245 of Rao and Nanjundiah 2010/2011. 25 Letter from Mayr to Haldane dated 13 April 1959 (No. HUGFP 74.7, Box 6, F 731; Pusey Library, Harvard University Archives, Cambridge, Mass., USA), footnote 29 on p. 244 of Rao and Nanjundiah (2010/2011). 26 Letter from Haldane to Mayr dated 30 December 1959 (no. HUGFP 74.7, Box 6, F 731; Pusey Library, Harvard University Archives, Cambridge, Mass., USA), footnote 41 on p. 249 of Rao and Nanjundiah (2010/2011). 27 Director, Anthropological Survey of India, January 1959–January 1964. See http://ignca.nic.in/ Lectures_PDFs/NKBose/NKBose007a.pdf. 123 Ernst Mayr’s interactions with J. B. S. Haldane

1.2 When did the beanbag genetics dispute begin?

According to VR/VN, it started in 1959; on p. 272 SS contains the statement ‘‘the dispute started with Mayr (1955) and not Mayr (1959)’’.In other words the claim is that the dispute began following Mayr’s talk at the Cold Spring Harbor Symposium in 1955, not the one he gave at the 1959 symposium. There are two points to note here. First, as far as we know, there is no report of the use of ‘‘beanbag’’ (in the context of population genetics) by Mayr before the 1959 talk. Second, if ‘‘dispute’’ is used in the common sense of ‘‘argument or disagreement’’, one imagines that it would require the engagement of at least two parties. The published version of Mayr’s 1959 talk was among the named provocations that induced Haldane to write Defense, although it was not the immediate trigger. Haldane (1964) does not refer to Mayr’s talk at the 1955 Cold Spring Harbor Symposium in Defense.28 On both grounds, then, 1959 seems to be the most appropriate date for marking the origin of the dispute. It is true that the roots of the dispute go back to before 1955. Waddington was one of those who had expressed a negative opinion of the mathematical treatment of genetics29; he repeated them in 1957 in The Strategy of the Genes (Waddington 1957).30 Dobzhansky and Lerner had spoken critically about population genetics at the Pavia meeting in 1953; Mayr and Haldane took part in the proceedings without making formal presentations (Haldane spoke at the banquet and wrote the Foreword to the subsequent publication).31 One might with equal justice say that the seeds of the beanbag genetics dispute were sown even earlier, in the beginning years of the twentieth century, when the better-known dispute between the Biometricians and Mendelians was playing out.

28 It was the published version of Mayr’s 1959 Cold Spring Harbor presentation too that elicited a strong objection to the ‘beanbag’ characterisation from Wright (Wright 1960), providing further justification for highlighting the significance of 1959. The immediate provocation for Haldane’s counter-attack appears to have been Mayr’s 1963 book ‘‘Animal Species and Evolution’’. Haldane cites it first in his paper, after which he moves on to the 1959 talk as ‘‘another place’’ in which ‘‘Mayr made a more specific challenge’’ (Haldane 1964). 29 Basically, that no ‘‘noteworthy quantitative statements about evolution’’ had emerged from it. As well, ‘‘qualitatively new ideas’’ had been ‘‘very few’’. See ‘‘The Dispute Anticipated’’ on p.244 of Rao and Nanjundiah, 2010/2011. 30 Mayr (1959) cites with approval Waddington’s misgivings regarding classical population genetics, and it may be this that SS may be referring to in saying ‘‘the elaboration of Waddington’s views later in The Strategy of the Genes (1957) had a direct role in emboldening Mayr’’. The information that Mayr had read Waddington’s critical remarks after they were repeated in 1957, and agreed with them, appears to have been communicated personally by Mayr to Sarkar (2007, p. 74, footnote 34). 31 Buzzati-Traverso (ed.) (1954). Dobzhansky and Lerner spoke in the 1953 Pavia symposium; both questioned the utility of population genetics theory based on Mendelian genes. As we have mentioned, Mayr shared their negative opinion and mounted his own attack later. Besides Mayr and Haldane, Fisher too was at the Pavia symposium. Like them, he did not contribute to the published proceedings either. Even if he did not make a formal presentation, he had ample opportunity to intervene and rebut the contentions of Dobzhansky and Lerner. It would be worth investigating whether he did so. See footnote 12 here and pp. 245–246 and footnote 34 on p. 246 in Rao and Nanjundiah 2010/2011. 123 V. Rao, V. Nanjundiah

1.3 How highly did Mayr regard Haldane?

The photocopies of two previously unpublished letters from Mayr to VR32 further testify to the extremely high regard in which he held Haldane.33 The first (M1) is dated 18 March 2004 and is typed; the second (M2), handwritten, is dated 28 September of the same year, when Mayr was about 100 years and 3 months old. The content of M1 overlaps partly with that of the Mayr typescript reproduced in SS. It states that Mayr and Haldane travelled together to Bhubaneswar and Puri and paid attention to people engaged in traditional occupations (brass making and painting are mentioned) as well as animals. Mayr was surprised by Haldane’s keen interest in natural history, and remarks that Haldane was angry at not being taken along on Mayr’s first bird-watching expedition. Mayr hints wryly at a possible reason for Haldane’s eventual falling out with P. C. Mahalanobis, Director of the Indian Statistical Institute (ISI) in Calcutta and in effect his boss: ‘‘Mahalanobis felt it would add to the prestige of his institute’’ if its address were to appear on ‘‘important papers’’ published by a ‘‘distinguished associate’’. But Haldane’s inclinations lay elsewhere: ‘‘to do something for the common man in Indian’’ [sic]; he taught ‘‘beginning genetics’’ to ‘‘poorly qualified students with infinite patience’’. Mayr remembers Haldane’s ‘‘dressing like any Indian, like Mahatma Gandhi’’.34 Interestingly, he remarks ‘‘When traveling by train he chose the lowest class, like the poor untouchables.’’ Here, as argued in SS, Mayr’s interpretation may have been off the mark. In the second letter, M2, Mayr states ‘‘I have been all my life a great admirer of J B S Haldane’’35 and ‘‘He was the most brilliant person I ever met’’.

1.4 How cogently did Mayr express his qualms regarding mathematical population genetics?

At the Cold Spring Harbor Symposium in 1955, Mayr called for ‘‘a new, inclusive population genetics that had not been fully developed yet’’ (Mayr 1955). In line with this sentiment, Dobzhansky wanted population genetics, which ‘‘was really launched in the thirties’’, ‘‘to expand its scope and develop a more realistic and more complex picture of the evolutionary process’’ (Dobzhansky 1955). Four years later, in the 1959 Symposium, Mayr drew a distinction between ‘‘classical population genetics’’ with its ‘‘gross oversimpliﬁcations’’, carried out during the ‘‘beanbag period’’, and the ‘‘newer population genetics’’ which ‘‘was characterised by an increasing emphasis on the interaction of genes’’ (Mayr 1959). Clearly he did not like the treatment of genes in isolation; later he expressed the view that ‘‘To consider genes as independent units is meaningless from the physiological as well as the evolutionary viewpoint. Genes not only act (with respect to certain aspects of

32 See Appendix. 33 Also stressed by VR/VN and SS. 34 Three words immediately preceding ‘‘like Mahatma Gandhi’’are scratched out in the original of M1. They appear to read ‘‘not a sati’’. Perhaps initially Mayr meant to write ‘‘not a saint’’. 35 Evidently, by ‘‘all my life’’ Mayr means the time since he first got to know of Haldane’s work and also met him, which was in 1947 as mentioned. See note 17 and related text. 123 Ernst Mayr’s interactions with J. B. S. Haldane the phenotype) but also interact’’ (Mayr 1963, p. 263). In 2002 he said ‘‘..taking genes in and out of a population is not the important thing because it’s individuals that really count’’ (Wilkins 2002, p. 962). In the 1959 talk he had cited, with approval, the work of Th. Dobzhansky, I. M. Lerner and K. Mather.36 For present purposes, these names may be associated with the concepts of ‘‘balance theory’’, ‘‘genetic homeostasis’’ and ‘‘genetic inertia’’, respectively. All three terms pertain to what one may call, in today’s terminology, systems-level properties of the genome that are dependent on interactions between genes and gene products; and, moreover, properties that are environment-dependent.37 From this one may surmise that what Mayr had in mind included phenomena such as chromosomal or polygenic inheritance and methods similar to those used in biometrical studies and quantitative genetics. Unfortunately he did not support his case by citing specific mathematical results from the ‘‘newer population genetics’’, and it is difficult to guess what examples he had in mind. One is left with the impression that his qualms were restricted to ‘‘oversimplifications’’. Overall, it remains unclear (except in the general sense mentioned above) what Mayr was objecting to. Nor does it appear that the objections persisted. In 1992 he asked, if only rhetorically, ‘‘..was the evolutionary synthesis (1936–1950) at all necessary after the excellent analyses of the evolutionary process by those three great mathematical population geneticists?’’(Mayr 1992, p. 176). The reference is to the contributions of Haldane, Fisher and Wright, presumably the ones made prior to 1936, as the word ‘‘after’’ indicates. He added ‘‘Some of Haldane’s greatest work was published after 1932. This includes … his series of papers on the cost of evolution’’ (Mayr 1992, p. 176). ‘‘Series of papers’’ implies that he had in mind not only Haldane’s 1937 paper on mutational load, but also the 1957 paper which discussed the substitutional load, which is puzzling in the light of his earlier criticism (see earlier discussion related to footnotes 9, 10). It is evident that Mayr was being inconsistent. Haldane offered one response to Mayr’s negative opinions; much before him, Wright had offered his own rebuttal. Both criticisms indicate signs of bafflement regarding Mayr’s stance.38

36 See footnote 31. 37 Mayr himself thought their approaches were harbingers of a new framework for evolutionary genetics that he called ‘‘the genetic ‘theory of relativity’’’ (Mayr 1959, alluding to Mayr 1955). Provine (2004) refers to the terms in the course of discussing what he calls Mayr’s ‘‘love/hate relationship with genetics’’. 38 Haldane (1964) and Wright (1960). Wright’s comments on Mayr’s 1959 address at the Cold Spring Harbor Symposium came the very next year in a review of the Symposium volume. They were worded strongly, beginning with ‘‘..he [i.e., Mayr] has seriously misinterpreted the roles of these various lines [of research in population genetics], as well as the contributions of the one with which I am most familiar’’, and going on to detail the misrepresentations. Haldane’s stance overlapped with that of Wright but was not identical (Rao and Nanjundiah 2010/2011). Provine states that in a 1986 interview Mayr ‘‘regret[ted] classifying Wright as a beanbagger, except in his one-locus-two-allele models. His physiological genetics, emphasis upon gene interaction, and shifting balance theory all were more congenial to Mayr’s views’’ (Provine 2004). Haldane (1964, Defense) seems to have been unaware of Wright’s riposte. In the Defense Haldane cites and lauds Wright’s contributions extensively. Along the way he remarks ‘‘Wright is one of the gentlest men I have ever met, and if he defends himself, will not counterattack’’ (which, as the quotation from Wright (1960) shows, was not true) and ‘‘If I have not defended Sewall Wright, this is largely because I should like to read his defense’’. 123 V. Rao, V. Nanjundiah

2 Summing up

J.B.S. Haldane and Ernst Mayr ﬁrst met in 1947 and soon became friends. Their friendship lasted until Haldane’s death in 1964 and was sustained by a shared interest in evolutionary questions and natural history. In between they met at several conferences, visited each other and carried out an extensive correspondence. A fundamental difference of opinion between them on the utility of (mathematical) population genetics, known as the ‘beanbag genetics dispute’, broke out in print shortly before Haldane died. Mayr’s chief objection was that elementary population genetics theory postulated ﬁtness effects due to each gene considered independently whereas interactions between genes were crucial for determining phenotypes. Haldane countered Mayr’s contention regarding the value of the approach vigorously; so did Wright, separately. Later on Mayr appears to have had a partial change of heart and his assessment of population genetics was not in accord with the earlier views. Two letters, written by Mayr shortly before his death as a centenarian, show that his already high admiration for Haldane was in no way lessened by the dispute. The beanbag genetics dispute illustrates the sorts of tensions that can arise when complex reality is sought to be grasped with the help of simple models.39

Acknowledgments VR thanks Ernst Mayr for graciously agreeing to provide his recollections of Haldane, and for interceding with the Harvard University Archives, Pusey Library, for permission to publish archival material. This contribution forms part of the research project titled ‘J. B. S. Haldane’s Indian Period’, supported by the Indian National Science Academy, New Delhi.

39 The tensions are all the more sharp when they involve, as they do in this case, the traditionally non- overlapping ﬁelds of biology and mathematics (discussed in Nanjundiah 2005 and Rao and Nanjundiah 2010/2011, p. 272 onwards). 123 Ernst Mayr’s interactions with J. B. S. Haldane

Appendix

(i) M1

123 V. Rao, V. Nanjundiah

(ii) M2

123 Ernst Mayr’s interactions with J. B. S. Haldane

References

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