The wild type as concept and in experimental practice: A history of its role in classical genetics and evolutionary theory
Section snippets
What are wild types?
The term ‘wild type’ is used in genetics to describe individual organisms or alleles deemed ‘normal’ or typical for their species. But more concretely wild type is what the standard lab strains of experimental organisms are commonly referred to as. These wild type strains operate as controls to measure variation in model organism systems. As the philosopher Rachel Ankeny observes (2007, pp. 49–50), without establishing a ‘wild type’ “it is not possible to have a ‘norm’ against which ‘abnormal’
Mayr, wild types and ‘typological thinking’
In many ways the principal ideologue of the Modern Synthesis, Mayr sought to demarcate the new evolutionary biology from its predecessors and competitors whilst also maintaining a clear link to Darwin's original thought. One means by which he did so was by invoking a dichotomy between ‘typological’ and ‘population thinking’ (Mayr, 1959). ‘Typological thinking’ (also conflated by Mayr with the broader ‘essentialism’), is the assumption that species are defined by an underlying and static ‘type’
A preliminary to wild type
The original gestation of the wild type concept can be traced to around 1800 (with the term first appearing in English in the 1820s) and was grounded in three main assumptions: (a) domestic organisms descend from wild ancestors; (b) domestication is an artificial state requiring human maintenance; and (c) the wild state is a species' natural state, towards which it is inherently inclined and will revert towards when removed from domestication (this representation of variation constitutes a kind
Weismann & Galton's sanctuarisation of heredity
Darwin's unified theory of variation presumed that domestication could serve as a useful source of information regarding variation in general, including in nature. However, in assuming a correlation between changes in the conditions of existence and organismic variation, Darwin implied that the character of wild types could not be kept stable for long-term study under domestic conditions. This was further assumed in his theory of generation, pangenesis, which proposed that changes to somatic
Mendelism and biometry: background to the dispute
Sanctuarisation and devitalization contributed to the growing confidence that organisms could be brought into controlled conditions and purified into stable strains characterised by a specific hereditary makeup. The large-scale methodical selective techniques Darwinism had valorised were moreover suffering diminishing returns, leading some plant breeders to resort to alternative methods, such as the mid-19th century Vilmorin strategy of pedigree line breeding. The commercial power of such ‘pure
Bateson contra weldon
William Bateson (1861–1926) was an early adopter of Mendelism and was one of its most prominent advocates in the early decades of the twentieth century, being responsible for organising the first translation of Mendel's papers into English. It has even been argued that given his better appreciation of the importance of Mendel's paper compared to the traditional ‘rediscoverers’ (de Vries, Correns and Tschermak), Bateson should therefore be regarded as Mendel's chief ‘rediscoverer’ (Keynes & Cox,
Bateson on the ‘presence and absence’ system, wild type and the ‘normal body’
Having examined the importance of wild type in Bateson's initial defence of Mendelism, I will now establish the centrality of the wild type concept in Bateson's overall genetic thinking by looking at a particular aspect of his thought that I believe is otherwise difficult to understand, namely his version of the ‘presence and absence’ model of dominance. This model suggested that in cases of complete dominance the recessive trait could be treated as ‘absent’, not inactivated. This was suggested
The Morgan group
The virtues of the 'presence and absence' system were threefold: its explanation of dominance as the imposition of presence over absence was easily understood; it did not invoke a virtus dormitiva as did property-based theories of dominance; and it retained a developmental and interactive role for factors, which was looked upon favourably by embryologists, most of whom favoured regulative models of development which presupposed that the cellular context, and not a pre-programmed parcelling out
Remodelling wild types & defending against critique
The story of how Morgan in early 1910 discovered the sex-linked mutant white, thus becoming convinced of the 1902 Sutton-Boveri hypothesis that chromosomes were the material carriers of factors, has been told elsewhere (e.g. Kohler, 1994). Morgan, once an arch-critic of the chromosomal hypothesis, was far from its first geneticist convert, but was first to make the key insight that the rarity of ‘complete coupling’ – the complete coinheritance of same-chromosome traits – could be explained as
Completing the decomposition of the wild type
The move to linkage mapping heralded a shift in genetics away from typological holism and towards instrumental interpretations of 'wild type' as relative to the particular trait or gene under study. This move towards relative or token wildness was accompanied by an increasing tendency to decompose wild types into ‘wild type’ genes and to ignore the role of gene-gene and gene-environment interactions in trait development. The transition from dynamic interactionism to a more static genocentrism
Conclusion
To summarise, how were lab wild types thought to represent nature's wild types? I earlier emphasised that there has been a long history of scientists using domestic organisms as stand-ins for wild ones. Darwin maintained, against orthodoxy, that wild and domestic varieties were produced through similar processes. His analogies were challenged by, among others, Weismann and Galton, but by promoting the sanctuarisation and devitalization of heredity, these theorists simultaneously encouraged the
Acknowledgements
I would like to thank my PhD supervisors Staffan Müller-Wille and Sabina Leonelli (this paper neatly summarises many themes covered in my thesis), as well as friends and colleagues with whom I have discussed my work, including Jim Lowe (who very helpfully reviewed a later draft of this piece), all the members of the University of Exeter's Egenis Centre for the Study of the Life Sciences, including the many participants of the University of Exeter's Biological Interest Group where I debuted an
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