Just the place for a Snark! I have said it twice:
That alone should encourage the crew.
Just the place for a Snark! I have said it thrice:
What I tell you three times is true.
Lewis Carroll, The Hunting of the Snark, 1876
The attitude of biologists to the history of their discipline varies. For some, a hazy knowledge of the recent past is all that is necessary to provide an explanatory basis for their work. They take it for granted that everything of value from the less recent past has been appropriately incorporated into present-day thinking. Other biologists see history as an integral part of their research: the historical roots of accepted facts and theories help in the evaluation of present positions. These biologists bring to history their specialized knowledge, which can be an advantage, but often they also bring an agenda that biases what they investigate and how they present it. We illustrate this by describing our own foray into history, which was motivated by findings in cell biology that suggested that some accepted views about heredity and evolution were wrong.
Introduction
As scientists who have spent much of their academic lives teaching biology and carrying out laboratory or theoretical studies of biological problems, it is almost inevitable that our approach to the history of our subject is different from that of professional historians of science. By training we are both geneticists, with a strong interest in evolution, and we have taught courses in both subjects. These courses always included historical elements, and were informed by some of the many books that have been written about the history of genetics and evolution. We relied on books like A Short History of Genetics (Dunn Reference Dunn1965), The Origins of Mendelism (Olby Reference Olby1985), The Evolution of Biology (Sirks and Zirkle Reference Sirks1964), The Logic of Living Systems (Jacob Reference Jacob1973), Evolution: the History of an Idea (Bowler Reference Bowler1989), and The Growth of Biological Thought (Mayr Reference Mayr1982). These and similar texts – some written by biologists and some by historians – also provided most of the material for a short course and series of radio talks on “The History of Heredity” that was given by one of us in the early 1990s (Jablonka Reference Jablonka1994).
It was thinking about findings from recent studies of chromosomes and gene activity, areas in which we did some of our laboratory work, that made us delve more deeply into the history of heredity and evolutionary biology. We have described the biology that led to this in our early publications on epigenetic inheritance (see Jablonka and Lamb Reference Jablonka and Lamb1989, Reference Jablonka and Lamb1995; Jablonka, Lachmann, and Lamb Reference Jablonka, Lachmann and Lamb1992), but it will be helpful here to give a brief outline. By the mid-1980s it had become clear that cell determination and differentiation were associated with induced, localized modifications of DNA (cytosine methylation) and chromatin structure. These changes affected the activity of genes, but did not alter DNA coding sequences – they were epigenetic changes, not genetic changes. Nevertheless, epigenetic marks, as the modifications were later dubbed, were often stably inherited in cell lineages, and plausible mechanisms had been suggested for how this could happen. In a seminal article published in Reference Holliday1987, Robin Holliday, one of the pioneers in the field of modern epigenetics, pointed out that if errors occurred during the production or inheritance of epigenetic marks, they could upset normal control mechanisms and transform somatic cells into cancer cells; epigenetic defects might also contribute to cell and tissue ageing, and, if errors occurred in the germ line, they would affect the next generation.
In the late 1980s, evidence that epigenetic marks could be transmitted transgenerationally was coming from molecular studies of genomic imprinting. With imprinting, what one sees is that the expression or transmission of a gene, a chromosome, or a chromosome segment depends on the sex of the parent from which it was inherited. For example, a particular gene that is inherited from the father might be active, whereas the same gene, with the same DNA sequence, would be inactive when inherited from the mother. The phenomenon was well known among geneticists, but unexplained. Interest in it increased when, in the early days of genetic engineering, it was discovered that transgenes – artificially inserted segments of DNA – often became imprinted. This was shown to be associated with different methylation marks on the maternal and paternal chromosomes. Even more interesting for biologists (but annoying for genetic engineers) was the finding that sometimes the inactivation of the transgene was permanent – it was not reversed when transmitted by the opposite sex.
The increasing evidence that (i) factors outside the cell can alter it in ways that are heritable, even though the DNA sequence remains unchanged; and (ii) some of these epigenetic changes can be transmitted to offspring, made us begin to question the prevailing dogma about the inheritance of acquired characters. We had been taught, and had taught others, that changes that were induced by the environment, or were acquired through the effects of use and disuse, could not be transmitted to the next generation. Not only was there no evidence for such “soft inheritance,”Footnote 1 it was also not to be expected because, as Weismann had explained decades earlier, the germ line becomes segregated from the soma early in development, and there was no known way that somatic changes could be transmitted via the germ cells to the next generation. Yet, the results from molecular biology were suggesting that there were mechanisms through which soft inheritance could occur.
The Dogmas
The belief that soft inheritance does not occur was very firmly entrenched when we started working on epigenetic inheritance in the 1980s. It was an integral part of the gene-based Modern Synthesis view of evolution that dominated in the second half of the twentieth-century. Nowhere can this be seen better than in the writings of Ernst Mayr, one of the creators of the Modern Synthesis, and also a leading historian of evolutionary thought. For example, in an historiographical article that was intended to show that Lamarck was a better observer and thinker than most people realized, Mayr's opening paragraph was:
As long as the battle between Darwinism and Lamarckism was raging, it was quite impossible to undertake an unbiased evaluation of Lamarck. For this we are now ready, after it has been demonstrated conclusively that the various causal explanations of evolution, usually designated as Lamarckism, are not valid. Not that it really needed this final proof, but the recognition that DNA does not directly participate in the making of the phenotype and that the phenotype, in turn, does not control the composition of the DNA, represents the ultimate invalidation of all theories involving the inheritance of acquired characters. This definitive refutation of Lamarck's theory of evolutionary causation clears the air. We can now study him without bias and emotion and give him the attention which this major figure in the history of biology clearly deserves. (Mayr Reference Mayr1972, 55)
Mayr gives no references for any of the strong claims about the gene-phenotype relationship that are made in this paragraph, but his earlier writings show where they came from.
By the late 1950s, most biologists had accepted that DNA is the genetic material, and genetic information is encoded in the sequence of its bases. Francis Crick made this view precise and clear in a famous lecture, “On Protein Synthesis,” delivered in 1957. In it he put forward two hypotheses. The first, which he said was widely accepted, was the Sequence Hypothesis, which assumes that the sequence of bases in a piece of nucleic acid is a simple code for the amino acid sequence in a protein. Crick's second hypothesis, which he acknowledged was not universally held, he called the Central Dogma:
This states that once ‘information’ has passed into protein it cannot get out again. In more detail, the transfer of information from nucleic acid to nucleic acid, or from nucleic acid to protein may be possible, but transfer from protein to protein, or from protein to nucleic acid is impossible. Information means here the precise determination of sequence, either of bases in the nucleic acid or of amino acid residues in the protein. (Crick Reference Crick1958, 153; italics in the original)
The implications of encoded information and the central dogma were not lost on Mayr, who a year or so later was writing:
It seems to me that the basic problem of Lamarckism, the inheritance of acquired characters, can be likewise stated far more clearly in terms of codes of information than it has been previously possible. If one wanted to demonstrate the occurrence of such inheritance, one would have to prove that the developmental pathway is not a one way street and, as Weismann emphasized some 70 years ago, one would have to prove that the information from the peripheral end organs is fed back to the germ cells in the gonads and is used to recode the inherited information in an adaptively improved manner. I hardly need to dwell on the extraordinary improbability of such an occurrence as far as the higher organisms are concerned. (Mayr Reference Mayr1959, 4)
In a similar way, John Maynard Smith, then one of the rising stars of British evolutionary biology, also latched on to the significance of the central dogma for ideas about the inheritance of acquired characters. He titled a new chapter in the second edition of his popular Penguin book, The Theory of Evolution, “Weismann, Lamarck, and the Central Dogma,” and in it declared:
. . . the process whereby information is passed from DNA to protein is now fairly well understood in chemical terms . . ., and it seems certain that this process could not work backwards. The greatest virtue of the central dogma is that it makes it clear what a Lamarckist must do – he must disprove the dogma. (Maynard Smith Reference Maynard Smith1966, 66)
Maynard Smith acknowledged that the inheritance of determined and differentiated states that were acquired during embryonic development was not dependent on nucleic acid differences, but deemed this type of inheritance too unstable to be of major importance in evolution.
By the mid-1970s, not only had findings in molecular biology been used to dismiss the possibility of the inheritance of acquired characters, but new ideas within evolutionary biology, particularly ideas relating to social evolution, had made it even more gene-centered.Footnote 2 Richard Dawkins’ The Selfish Gene (Reference Dawkins1976) helped to spread and consolidate the gene-centered view of evolution. It was this view, which the evidence coming from laboratory studies made us think was mistaken, that encouraged us to look into the historical origins and development of modern ideas about heredity and evolution.
Approaching History: The Pros and Cons of Being a Biologist-Historian
Our investigations into the history of biology have been guided by the present and orientated towards the future. In historical circles, this approach would probably be described disparagingly as whiggish. Nevertheless, what we wanted to understand was how biologists had reached the consensus view that there is no soft inheritance, and where the conviction came from that the only type of hereditary variation that is significant in evolution is that resulting from random gene mutations and their shuffling during sexual processes. As geneticists, we were aware of several examples of non-Mendelian inheritance for which there was no adequate explanation (they were mentioned in the textbooks), and we wondered how many other cases had been reported but forgotten. Therefore, one of the first things we did when we started working on epigenetic inheritance in the 1980s was to scour the old genetics literature for possible cases of soft inheritance. We were also aware that in the early decades of the twentieth century there had been many debates about Lamarckism, and by studying the literature we hoped to understand how it had subsequently become such a no-go area for biologists.Footnote 3
Our explorations of the history of heredity were obviously shaped by our scientific interests. Like many biologists who start looking into the historical development of their subject, we had an agenda, and what we have read and where we have looked have been strongly influenced by it. Moreover, there has been a constant interplay between the biology we are thinking about and the history we try to trace: our biology feeds into and feeds on its history. Consequently, although for orientation and leads into the literature we have relied heavily on the writings of historians of biology such as Peter Bowler, Robert Olby, Jan Sapp and others, we have also been led into different historical avenues by the writings of biologists. For example, the influence of Weismann's “doctrine of the continuity of the germ line” on the Modern Synthesis view of evolution became clear to us initially through Leo Buss's contribution to the units-of-selection debate in the 1980s. Buss pointed out that:
Although Weismann's doctrine was the subject of two very critical reviews in the 20th century . . ., these criticisms fell on deaf ears amongst the excitement surrounding the new field of genetics, and Weismann's doctrine became dogma. (Buss Reference Buss1983, 1387)
Buss went on to summarize data showing clearly that for most organisms Weismann's doctrine was simply an unsupported assumption. His conclusion made us read Weismann's books and the works of his critics, and this old literature convinced us even more that soft inheritance was likely to have been important in the many groups of organisms in which differentiated cells remain totipotent.
Our historical sources have been limited almost entirely to published papers and books from the nineteenth and twentieth centuries. We have made very little use of archival material because, as biologists, we are most at home in the primary literature, where we feel competent to find, evaluate, and interpret work that often has been rarely cited, is incorrectly cited, or is concealed by what, for our interests, is an uninformative title. The same questions about soft inheritance can be articulated in many ways, and interesting data and relevant ideas can sometimes be found lurking in papers whose titles refer to “carry-over effects,” “epigenetic systems,” “position effects,” “imprinting,” “paramutation,” “dauermodifications,” and so on. This is where, as biologists, we have an advantage. A historian who is not thoroughly immersed in biology might miss the significance of some of this work and the relationships between the different terminologies. Indeed, terminological differences sometimes mean that biologists themselves take time to appreciate that the phenomena described in one subdiscipline are related to those described in different terms in another subdiscipline. For example, it took time to recognize that “co-suppression” in plants, “quelling” in fungi, and “post-translational gene silencing” were all manifestations of an epigenetic process now known as RNA interference (Sen and Blau Reference Sen and Blau2006).
A second sphere in which we think that biologists are able to make a contribution to understanding the historical development of their subject is almost the opposite of that just discussed. Biological knowledge makes it easier to recognize when particular terms or concepts are being used in different ways. For instance, there have been multiple meanings given to “innate,” and biologists are in a good position to clarify this concept (Bateson and Mameli Reference Bateson and Mameli2007). Although professional historians of biology can and do make exceptionally good conceptual analyses, which are often far less biased than those made by biologists, the biologist-historian's hands-on acquaintance with their subject matter is sometimes overwhelmingly important. It is very unlikely that anyone other than a professional microbiologist with an intimate knowledge of the experimental procedures used could have dissected the changes in ideas about bacterial variability in the way that Ludwik Fleck did (Fleck [1935] Reference Fleck, Trenn, Merton, Bradley and Trenn1979, 87–94).
Another important role for the biologist-historian is to question the historiography of a subject. We have acknowledged that when looking into the history of our discipline, we have had an agenda, and, whether admitted or not, we think that this is true for many biologist-historians. The description of a biological development, its roots, its influence, its scientific soundness, and its importance are inevitably influenced by the biologist's beliefs and opinions. This can lead to problems of bias. Elsewhere we have referred to one aspect of this as the “Churchill factor” (Jablonka and Lamb Reference Jablonka2011), because Winston Churchill, the British wartime leader, is reported to have said “History will be kind to me, for I intend to write it.”Footnote 4 We think the Churchill factor is very evident in the writings of many biologist-historians, including both acknowledged historians like Ernst Mayr, and occasional historians who contribute historiographical essays to anniversary volumes and journals such as Genetics and BioEssays. We do not underestimate the value of these contributions, but believe they need to be treated with caution. When the palaeontologist George Gaylord Simpson reviewed Mayr's massive history The Growth of Biological Thought, he described it as “Autobiology.” Simpson was a contemporary of Mayr, and a fellow founder of the Modern Synthesis, but in his eyes, “This book is in an unconventional and highly unusual way an autobiography. In it Mayr is seeking out, cleverly and successfully, the roots of his own accomplishments and opinions” (Simpson Reference Simpson1982, 438). As a biologist, Simpson was in a strong position to recognize some of the imbalances and inaccuracies in Mayr's history. Whereas most reviewers of Mayr's book discussed matters such as the way he approached history, the book's organization, its stylistic quirks, its purpose, and its contribution to the philosophy of biology – responses that were undoubtedly encouraged by the early chapters in which Mayr spelt out what he wanted to do – it was mainly (although certainly not exclusively) the biologist-reviewers who also criticized the biological and historical detail.Footnote 5 Simpson questioned aspects of Mayr's treatment of taxonomy and systematics, and pointed out a mistake in the description of the stance Simpson had taken in debates about the relation between phylogeny and classification. The British zoologist Arthur Cain (Reference Cain1982) insisted that Mayr had not given enough weight to the botanists’ long-standing objections to Weismannism, or to their belief in the importance of polyploidy in plant speciation; he also reminded his readers that, contrary to any impression that Mayr's book might give, there had been hardly any work on natural selection in the wild. Similarly, in their reviews of Mayr's book, evolutionary biologists John Maynard Smith (Reference Maynard Smith1982) and Douglas Futuyma (Reference Futuyma1982) both felt that Mayr had underplayed the significance of the mathematical theorists in the history of modern evolutionary biology.
Because of their detailed knowledge of the science involved, biologists are able to question the evidence and emphases found in historical analyses, particularly those of fellow biologists who are writing about the development of fields to which they have contributed. Nevertheless, they rarely do so. The historical essays in scientific journals, which are often written by scientists who are eminent in the field, are subject to little scrutiny and criticism, and their selectivity, biases, and inaccuracies usually go publicly unchallenged.
Although biologist-historians possess the biological knowledge that enables them to question historical accounts of their subject, the downside to their work is that their approach is very narrow. For example, in our own studies, we have made little use of archival material. This is partly because we do not have the work habits of professional historians, who base much of their work on archives, but also because we are not sure how to handle the unbalanced nature of the material available. Some significant figures have left no lab notebooks, unpublished papers, or letters for historians to mine, whereas others seem to have recorded and hoarded everything from their unsuccessful grant applications to their doodles. We realize that the haphazard nature of the archives is a problem for all historians, but it is not clear to us how, when aiming for a general picture of changing attitudes to soft inheritance, we should deal with it. It would certainly be interesting to study personal archives, particularly of people whose work we feel has been underappreciated, but the archival materials that we would find most valuable, if available, would be those that provide information about papers that were rejected, as well as accepted, for publication. So far, however, we have studied only papers and books that have been published; we assume that, in spite of the limitations, from the published literature we can get a relatively unbiased measure of the acceptability and prevalence of ideas about soft inheritance, as well as the evidence for it.
As non-historians, our ability to deal with the social, political, scientific, and general intellectual milieu that influenced the nineteenth- and early twentieth-century work we are interested in is limited. We have to rely on what has been written by contemporaries and present-day historians. However, we were active biologists for most of the second half of the twentieth century, so we have our own records and memories of that period. Our experience enables us to understand the methodologies used by working biologists. We know, for example, how highly selected the published photographs of cytological preparations usually are; how arbitrary the designation “lethal mutation” can be in fruit fly mutagenesis studies; how frequently experiments “fail” (to give the expected result); and how biologists explain away these “failures.” We have also known and interacted with some of the leading figures in twentieth-century biology, often before they achieved hero status. So we know, sometimes first hand and sometimes second hand, about some of the rivalries between particular scientists; about how ambitious they were; about their political beliefs; about how they interacted with senior and junior colleagues; about how receptive or otherwise they were to new ideas, and how they reacted to criticism. As insiders, we are therefore aware of many aspects of the context in which genetics and evolution research was taking place, and of some of the internal, social-historical factors that made, and still make, it difficult for biologists to recognize and challenge existing dogmas.
Neglecting History
As we see it, one of the main reasons why dogmas persist is associated with the way scientists handle history in their publications. There is a sense in which any creative biologist has to be, or pretend to be, a historian of their subject. We report the outcomes of experiments and observations in scientific journals, and our papers have a traditional structure. First there is an “Introduction,” then “Materials and Methods” are described; next come “Results,” and finally a “Discussion” of the significance of the data. The whole is accompanied by a Summary and/or Abstract, and References or Notes that give the bibliographic details of the work that has been cited, i.e., of the historical background to the research. Most of this is given in the Introduction, which includes what the immunologist Peter Medawar once described as “a section called ‘previous work’ in which you concede, more or less graciously, that others have dimly groped towards the fundamental truths that you are now about to expound” (Medawar [1963] Reference Medawar1991, 228).
Medawar tried to explain the failure of scientists to acknowledge the importance of work done by their predecessors. In a review of James Watson's The Double Helix (Reference Watson1968), he highlighted the fact that the author made no mention of Frederick Griffiths’ discovery of pneumococcal transformation, a key finding in the recognition that DNA is the hereditary material, and asked why. His answer was:
It was not lack of generosity, I suggest, but stark insensibility. These matters belong to scientific history, and the history of science bores most scientists stiff. A great many highly creative scientists (I classify Jim Watson among them) take it quite for granted, though they are usually too polite or too ashamed to say so, that an interest in the history of science is a sign of failing or unawakened powers. It is not good enough to dismiss this as cultural barbarism, a coarse renunciation of one of the glories of humane learning. It points towards something distinctive about scientific learning, and instead of making faces about it we should try to find out why such an attitude is natural and understandable. A scientist's present thoughts and actions are of necessity shaped by what others have done and thought before him; they are the wavefront of a continuous secular process in which The Past does not have a dignified independent existence on its own. Scientific understanding is the integral of a curve of learning; science therefore in some sense comprehends its history within itself. No Fred [Fredrick Griffiths], no Jim [James Watson]: that is obvious, at least to scientists; and being obvious it is understandable that it should be left unsaid. (Medawar [1968] Reference Medawar1972, 104–105)
If, as Medawar suggested, and was argued much earlier by Ludwik Fleck (1935), the present scientific understanding of a subject is structured by its history and has The Past embedded within it, then for most scientists the historical origins and development of their work and belief systems are unknown and seem unimportant. They become important only when something is discovered that appears to be at odds with prevailing beliefs and theories, and is sufficiently sound and striking for it not to be ignored or explained away. When this happens, exploring the past and discovering what led to the currently held views becomes more relevant, and presenting and assessing earlier work and ideas becomes less of an academic ritual, and more of a necessity.
The problem for biologists is that tracing the past development of a subject is not always easy, simply because the background given in experimental papers is commonly misleading and inaccurate. A few years ago, Tim Birkhead, a behavioral ecologist, wrote about younger researchers:
Typically, they might refer to a topic such as sexual selection (first enunciated by Darwin in 1871) but rather than citing Darwin, will refer instead to a recent paper by another author who happens to mention, however tangentially, sexual selection. A second kind of mis-citation is citing oneself, one's colleagues or members of one's intellectual clique, rather than citing the most appropriate reference. (Birkhead Reference Birkhead2008)
Birkhead suggested several reasons for young scientists’ inappropriate citations, ranging from laziness to deliberate deceit aimed at enhancing the novelty of their own work. Naturally, he condemned it: “Not citing the literature appropriately is poor scholarship and perverts history.”
Inadequate, inappropriate, and inaccurate use of citations is not restricted to young researchers, however, and it is not a new problem, although the recent use of citation-based metrics to evaluate journals, authors, and their institutions has probably made the problem of the selective and misleading citation worse (Lawrence Reference Lawrence2007, Reference Lawrence2008). For decades biologists have been relying on information given in review articles and books, rather than extracting it from the primary literature. This may be unavoidable when trying to summarize many papers in an article for a journal whose editorial policy restricts the number of words or references that can be used. Often, however, authors cite work they have not read, or have not read very carefully. Peter Lawrence (Reference Lawrence2007) looked at forty-eight papers in which a particular article that he had co-authored was cited, and found that only eight accurately represented what had been reported; three of the papers he described as “plain wrong” about what was said, and the remaining thirty-seven could or should have cited a different article.
The sometimes sloppy and often inadequate way in which scientists present earlier work can too easily lead to the spread of unsound information. Steven Greenberg (Reference Greenberg2009) analyzed the way in which a particular belief for which the evidence was not strong spread through the literature during a twelve-year period.Footnote 6 Using a network analysis of 242 papers and 675 citations, he showed there was substantial citation bias. Papers presenting data that weakened or refuted the claim were rarely cited, or, if cited, their contents were distorted. Often, what in the original publications were hypotheses were cited as “facts.” A small number of review papers were enormously influential in establishing the belief, although they presented no new findings. Greenberg thought that many authors may not have been aware of the data that did not support the belief, since they were not mentioned in the review articles.
Challenging Received Views: The Effects of Authority
Because biologists are rarely concerned with the historical basis of accepted facts and beliefs, once unsound information and ideas are embedded in the literature, correcting or countering them can be difficult. Dogmas remain unchallenged for decades, particularly when they are associated with the names of giants in the field. A good example is the (false) belief that humans have 48 chromosomes.Footnote 7 The first estimates of human chromosome number varied, mainly around 24, but in the early 1920s Theophilus Painter concluded there were 48. Painter went on to pioneer the use of Drosophila polytene chromosomes for gene mapping, and became one of the leading cytogeneticists of his day. Initially not everyone agreed with his chromosome count, but,
. . . Painter's authoritative chromosome studies in the 1920s were a very strong influence on all other cytologists in their counts of human chromosomes. Cytologists firmly expected to find 48 chromosomes and, in haploid cells, 24 chromosomes. Not surprisingly, in view of the trying technical circumstances, they found them. A close preconception-confirmation feedback relationship was established. Preconception led to confirmation; confirmation strengthened the underlying preconception; the strengthened preconception increased the likelihood of further confirmation which was, indeed, forthcoming. (Kottler Reference Kottler1974, 484–485)
So convinced were cytologists that the correct chromosome number for humans was 48 that very few studies were published in the 1940s and early 1950s. Then, in 1956, using different techniques, it was shown unambiguously that the chromosome number was 46. By the end of the decade, this had been confirmed many times, and it had also been shown that congenital conditions such as Down's, Turner's, and Klinefelter's syndromes were associated with atypical chromosome numbers. The new techniques had been instrumental in destroying the 30-year-old dogma, and initiating the development of the field of human cytogenetics.
A dogma that persisted for even longer than this was that of the potential immortality of cells in culture.Footnote 8 In the late-nineteenth century, August Weismann argued on theoretical grounds that somatic cells, unlike germ cells, had only a limited ability to survive and reproduce. However, in 1912, the year in which he won the Nobel Prize for his surgical work, Alexis Carrel claimed to have developed a method that, with a little modification, would allow tissue cultures to survive indefinitely. Over the following years, Carrel and his colleagues introduced improvements into the already elaborate and laborious techniques, and reported in both the scientific and popular press on the progress of the chick embryonic heart cultures he had described in 1912. One of these survived until 1946. No one else had such success with their cultures, but it was easy to attribute failures to technical deficiencies, contamination, or accidents. However, doubts about the dogma of the immortality of cultures of normal cells were given substance in the early 1960s when, using relatively simple techniques, Leonard Hayflick and Paul Moorhead showed that normal fibroblast cells, unlike cancer cells, had only a limited capacity to replicate. They suggested that this was a manifestation of senescence at the cellular level, and soon a new field, cytogerontology, was blossoming.
The survival of Carrel's cultures has been attributed to the inadvertent or deliberate introduction of new cells during their maintenance (Witkowski Reference Witkowski1980). Whatever the cause of their longevity, Carrel's cultures, and the publicity he gained for them, undoubtedly affected the development of ideas about ageing:
Had they [Carrel and his co-worker Albert Ebeling] not committed themselves so firmly to the idea that somatic cells do not age and worked so assiduously to sustain this view, it seems likely that tissue culture systems for examining the validity of Weismann's predictions would have been developed much earlier. If this had been the case, it is probable that we would now know considerably more about ageing in different types of somatic cells and about the relationship between cellular and whole animal ageing than we do. (Kirkwood and Cremer Reference Kirkwood and Cremer1982, 113)
History for Biologists
It is always difficult to know the extent to which adhering to conclusions based on insufficient or unsound evidence has hampered progress in a field. Dubious dogmas that are generated, accepted, or propagated by influential scientists like Painter, Carrel, Mayr, or Crick can become very entrenched. The status of such eminent people means they have many opportunities to talk and write about their ideas, and thus reinforce them. Too often, their views are adopted uncritically by other scientists, whose thinking they bias.Footnote 9 Directly or indirectly, they affect what gets published and which research projects get funded, thereby constraining the direction of research. Isaac Newton wrote “If I have seen further it is by standing on the shoulders of giants,”Footnote 10 but sometimes rather than providing helpful shoulders, the giants in science may obstruct the view of the best way ahead.
This is why studying the history of a field can be so important for scientists. It can help to widen the perspective by re-opening discussions of problems that have been forgotten or buried, either because the received opinion is that they have been solved or are irrelevant, or simply because they have become unfashionable. Commonly the stimulus to look into history comes from new techniques which produce new findings that re-initiate interest in a problem. In our case, it was the results from molecular biology that suggested a mechanism through which soft inheritance could occur. By looking into the old literature, we found that, in spite of the loud denials of Ernst Mayr and his followers, there was plenty of good circumstantial evidence for soft inheritance. We also discovered that some well-respected mid-twentieth century biologists had recognized that an epigenetic perspective was necessary to understand evolution.Footnote 11
The outcome of our initial studies of the old literature was that in the early 1990s we were able to produce a paper titled “Evidence, mechanisms and models for the inheritance of acquired characters” (Jablonka, Lachmann, and Lamb Reference Jablonka, Lachmann and Lamb1992). In it, we presented the old data alongside the recent data (which were scant), and used them to construct models and suggest mechanisms through which soft inheritance could occur. Inevitably, this work led to an attempt to understand the history behind the neglect of the old observations and ideas. Here, our debt to historians who have studied the people, institutions, and the social factors that have influenced developments in biology has been great; they have made recognizing, and to some extent understanding, the twists and turns that have led to biologists’ present views about heredity and evolution a manageable task. We incorporated some of their work in our first book, published in 1995, which was titled – perhaps unwisely, but very deliberately – Epigenetic Inheritance and Evolution: The Lamarckian Dimension. In this book and many of our other publications, we have used a historical perspective to alert fellow biologists to the insubstantial foundations on which some biological dogmas about heredity and evolution are based, thereby bolstering our views about the importance of epigenetic variation. For us, historical research is a tool, rather than an end in itself.
As biologist-historians, we have written almost entirely for biologists, although we hope that we have alerted historians to some problems that might interest them too, and that we have been a useful conduit between professional historians and biologists. From a historian's perspective, our approach can be seen as thoroughly whiggish, because we use the past to try to understand the present. However, we do not study the history of the “victories” that led to the present view of heredity and evolution. On the contrary, we have tried to illuminate what we see as the biases in present-day biology by looking at the maze of old information and past ideas that have been ignored or deemed wrong. The advantage of this approach is that we sometimes unearth data that have been neglected by both biologists and historians, and identify paths of enquiry that have been seen as dead ends. The disadvantage is that, although focused, our approach is very limited. We certainly do not see it as the “Right” method for doing historical research in biology. The biologist's way and the professional historian's way of viewing history are, and should be, complementary. We agree wholeheartedly with Ludwik Fleck, who wrote, “the current state of knowledge remains vague when history is not considered, just as history remains vague without substantive knowledge about the current state” (Fleck [1935] Reference Fleck, Trenn, Merton, Bradley and Trenn1979, 54).
