Abstract
Philosophers have the impression that evolutionary medicine is plagued by naive adaptationism (e.g., Murphy 2005, Valles 2011, Méthot 2012), leading to poor science through the proliferation of untestable ‘just-so stories’ and to poor medicine through not considering alternative explanations with different medical implications. It is therefore predictable that, given the centrality of optimality modelling to contemporary nutritional ecology, these criticisms will be applied, mutatis mutandis. It is also predictable that because it utilises the concept of ‘mismatch’ between mechanisms governing dietary choice and nutritional environments, nutritional ecology will be criticised for invoking an ‘environment of evolutionary adaptedness’ (Buller 2005). Such criticisms are understandable, because naive adaptationist reasoning occurs in both ‘popular nutrition’ – self-help books and lifestyle gurus – and in traditional nutrition science. However, the solution for this is not less evolutionary thinking, but more, as nutritional ecology demonstrates. Valles (2011) argues that evolutionary medicine is committed to ‘empirical adaptationism’ (Godfrey Smith 2001), the view that forces other than natural selection can be neglected in the explanation of organismic form. One of Valles’ examples is the now exploded ‘promiscuous primate’ hypothesis about menstruation (Profet 1993). But the work which refuted that hypothesis, and which used adaptationist reasoning to establish constraints on the evolution of endometrial reabsorption, is equally part of evolutionary medicine (Strassman 1996). In a similar vein we show that the prominence of optimality analysis and related methods in nutritional ecology does not reflect on a commitment to strong empirical adaptationism. It reflects both ‘methodological adaptationism’, a powerful tool for revealing constraints on natural selection, and ‘explanatory adaptationism’ – an explanatory focus on the observed degree of adaptation. Nutritional ecology examines the interactions of animals with nutritional environments (Raubenheimer and Simpson 2012). It makes extensive use of the idea that nutritional regulatory phenotypes and their teleonomic goals (‘intake targets’) are 1) an important determinant of evolutionary fitness, 2) therefore reflect a history of natural selection and 3) thus contain information about the interplay of optimization and constraint in evolution. It is explicitly and importantly a multi-scale theory, which studies the adjustment of organisms to their nutritional environments on scales ranging from minutes (e.g., homeostasis) to lifetimes (e.g., phenotypic plasticity), across generations (epigenetic inheritance) and in evolutionary time (gene selection). Since the causal interaction of species with their environments is bidirectional, nutritional ecology also makes use of gene-culture coevolution and niche construction when explaining nutritional phenotypes. Nutritional ecologists have examined these issues extensively in laboratory and field studies. Understanding the actual ways in which nutritional ecology is ‘adaptationist’ will provide a safeguard against what we might call ‘naive anti-adaptationism’, the failure to appreciate the methodological sophistication with which researchers use optimality analysis and related methods. Our discussion is therefore an example of the idea at the heart of this symposium – that nutrition science is a rich and productive field for interaction between philosophy and science.
