The Concept of Exaptation Between Biology and Semiotics

72 International Journal of Signs and Semiotic Systems, 2(1), 72-87, January-June 2012

The Concept of Exaptation between Biology and Semiotics

Davide Weible, Tartu University, Estonia

ABSTRACT

This paper explains what the biological concept of exaptation is by providing the theoretical context within which it was formulated and the definition of its meaning with respect to other related notions adopted in evolutionary biology. At the same time, this paper describes the main stages of its further development from the initial introduction and outlines its wide contemporary usage within fields of research other than biology. Finally, specific attention is paid to the linguistic, semiotic and biosemiotic dimensions of its adoption, concluding with a discussion concerning the relationship between exaptation and biosemiotics and furnishing some clues for a possible direction of inquiry in the tradition of a Peircean semiotic approach.

Keywords: Abduction, Biosemiotics, Cooption, Creativity, Evolutionary Biology, Exaptation, Semiotics

INTRODUCTION–A DIFFERENT a core part of the Modern Synthesis or Neo- POINT OF VIEW IN Darwinism in 1930s, generally proceeds in two EVOLUTIONARY BIOLOGY step: first of all, “an organism is atomized into ‘traits’ and these traits are explained as struc- In 1979 the American paleontologist S. J. Gould tures optimally designed by natural selection and the American evolutionary biologist R. C. for their functions”; secondly, when a trait is Lewontin published the article The Spandrels considered not as an isolated element but with of San Marco and the Panglossian Paradigm: reference to the whole it belongs to, “interaction A Critique of the Adaptationist Programme. is acknowledged via the dictum that an organism In that paper they stressed a need for change cannot optimize each part without imposing in the way of thinking about the evolutionary expenses on others. The notion of ‘trade-off’ process and of conceiving the mechanism of is introduced, and organisms are interpreted as natural selection as the main cause of nearly all best compromises among competing demands” organic forms, functions and behaviours, thus (Gould & Lewontin, 1979, p. 585). In a way as able to forge the best among possible worlds. analogue to the kind of explanations given by The “adaptationist programme,” as they Dr. Pangloss, Candide’s tutor in Voltaire’s novel call it by referring to an account popularized by Candide, ou l’Optimisme (1759), for whom “our Wallace and Weismann and eventually become noses were made to carry spectacles, so we have spectacles”, the adaptationist programme there- fore concludes that everything in an organism DOI: 10.4018/ijsss.2012010103

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“plays its part and must be what it is” (Gould but it holds that constraints restrict possible & Lewontin, 1979, p. 585). paths and modes of change so strongly that Even though constraints upon the possible the constraints themselves become much the pathways of evolution shaped by natural selec- most interesting aspect of evolution.” (Gould tion are doubtless recognized, nevertheless they & Lewontin, 1979, p. 594) are overshadowed by “styles of argument”, namely mental attitudes constantly pushing By emphasizing the importance of phyletic, towards the same explanatory conceptual developmental and architectural constraints framework: “if one adaptive argument fails, (Gould & Lewontin, 1979, pp. 594-595) and, try another”; “if one adaptive argument fails, accordingly, underlining the possibility of an assume that another must exist; “in the absence epiphenomenal origin of some adaptations of a good adaptive argument in the first place, (traits which are by-products of constraints attribute failure to imperfect understanding of and only subsequently, as already available where an organism lives and what it does”; parts, become useful for a particular function), “emphasize immediate utility and exclude other Gould and Lewontin charged the adaptationist attributes of form” (Gould & Lewontin, 1979, programme – and thus Neo-Darwinism – with pp. 586-587). failing to distinguish current utility from causes In order to contrast this model, on one for origin. In this way, they paved the way to the hand Gould and Lewontin presented a “Ty- next logical step as well, namely the conceptual pology of Alternatives to the Adaptationist emphasis and the terminological founding of Programme” (Gould & Lewontin, 1979, p. 590), exaptation as the property of a trait to be use- which encompasses five different alternative ful for a function not by (exclusive) means of evolutionary combinations with respect to the natural selection. adaptive and selective nature of a peculiar trait: As for the consequent reinforcement of a “no adaptation and no selection at all”; “no complementary point of view in evolutionary adaptation and no selection on the part at issue; biology and the framing of a post-Darwinian form of the part is a correlated consequence of evolutionary epistemology, the Italian episte- selection directed elsewhere”; “the decoupling mologist T. Pievani has strongly pointed out the of selection and adaptation” (with the two core function of the concept of exaptation in sub-cases of adaptation without selection or such a design. On one side, thanks to it selection without adaptation); “adaptation and selection but no selective basis for differences “Two major dogmas of the neo-Darwinian among adaptations”; “adaptation and selection, program are irreversibly put on trial: pro- but the adaptation is a secondary utilization gressionism, or the idea that evolution can be of parts present for reasons of architecture, represented on a gradual, ascending ladder, development or history”. and adaptationism, or the idea that morphol- On the other hand, they claimed for a ogy represents a functional optimization of the theoretical and methodological retrieval of the organic structure in relation to its environment.” morphological-structural current of European (Pievani, 2002, p. 325, 2003, p. 75) biology and its approach to evolution, accord- ing to which On the other side, along with the theory of punctuated equilibria – which affirms the “The basic body plans of organisms are so diversification and stratification of evolution- integrated and so replete with constraints upon ary rhythms – and the hierarchical theory of adaptation […] that conventional styles of se- evolutionary levels – which diversifies the units lective arguments can explain little of interest accountable for the origin of the evolutionary about them. It does not deny that change, when change, the concept of exaptation redefines in it occurs, may be mediated by natural selection,

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