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Evolutionary Psychology: A Review

5. Current Challenges for Evolutionary Psychology

The first difficulty for Evolutionary Psychologists centres on their claims about the environment of evolutionary adaptedness (EEA) from which the current adaptations in our cognitive structures are argued to have evolved. Evolutionary Psychologists claim that the last 10,000 years comprising the modern era is insufficient time for new structures to develop [Cosmides and Tooby 1987: 280; Tooby and Cosmides 1989: 34]. However, this amounts to some 400 generations and it is an empirical question whether significant changes to structures can occur within this time. The Evolutionary Psychologists' insistence that the modern period comprises less than 1% of our total evolutionary development is irrelevant if there had been significant selective pressures during this time.[8]

A second line of argument comes from behavioural ecologists, who argue that the Evolutionary Psychologists' conception of adaption is overly restrictive. For behavioural ecologists, such as Buller [2005b], selective pressures can act directly on behavioural traits, short-circuiting the Evolutionary Psychologists' need for specific information processing modules. Buller's notion of phenotypic plasticity is a serious candidate for explaining the wide range of human behaviours without recourse to the evolution of specific cognitive structures for each of those behaviours.[9]

Book cover: Alas, Poor Darwin: Arguments Against Evolutionary Psychology by eds H. Rose and S. Rose

In §3 above, I summarized the Evolutionary Psychologists' arguments for the massive modularity hypothesis; the theory that there are a large number of content-specific cognitive mechanisms that evolved to solve very specific problems in the EEA. This hypothesis gets some support from findings in cognitive psychology. For example, the brain contains separate specialized circuits for analysing the shape of objects, detecting the presence of motion, detecting the direction of motion, judging distance, analysing colour, identifying an object as human, recognizing your mother's face, and so on.[10]

Critics such as Samuels [1998: 587] make the point that a small number of domain-general cognitive mechanisms could have evolved that performed their operations on innate domain-specific information. This criticism is lent weight by recent advances in our knowledge of how the brain develops. Researchers don't see a positive correlation between brain complexity in mammals and genome size (the number of genes). And most of these genes are not dedicated to building specific structures in the brain. It appears that the shape and function of specific structures is the result of pruning, mostly of brain cells that are not interacting with the environment, and outside the ambit of direct gene control.[11] Just how many domain-specific mechanisms there are and how wide the scope is of domain-general mechanisms are open empirical questions that will only be answered by further research.

The fourth kind of argument levelled at Evolutionary Psychologists is that they have not demonstrated that their explanations for current human behaviour are the only ones or the most probable. Gould has labelled the Evolutionary Psychologists' explanations as 'just-so-stories' [Gould and Lewontin 1979; Gould 2000: 119]. I think this criticism is not entirely fair.[12] With the three experimental studies mentioned in the previous section, the Evolutionary Psychologists conducted a functional analysis of a perceived problem faced by our ancestors in the EEA and predicted a computational algorithm that would have solved the problem. The prediction was then tested in the laboratory. As Sell et al [2003: 48] put it, using the predictions derived from their functional analysis the Evolutionary Psychologists 'devise experiments that make possible the detection and mapping of mechanisms that no one would otherwise have thought to test for in the absence of such theories'. These studies are exemplars of good scientific practice for empirically supporting a theory. Of course, that still leaves a lot of analyses offered by Evolutionary Psychologists that do not fit this mould.

A related criticism of the Evolutionary Psychologists' approach concerns the uncertainty of our knowledge about what conditions were like during the EEA. The critics' argument is this. Without the particulars about social structures, task differentiation between males and females, kinship relations, and so on, any kind of functional analysis on which conclusions about cognitive structures are based is highly conjectural [Gould 1997: §31; Gould 2000: 120). I don't think this objection stands. In testing scientific theories, theories are not tested in isolation. In the case of the Evolutionary Psychology programme, the hypotheses specifying conditions during the EEA are auxiliary hypotheses that are tested at the same time as the core theory. In fact, posited conditions at the EEA form part of the positive heuristic of the Evolutionary Psychologists' research programme. When novel predictions from the theory are confirmed, the auxiliary hypotheses about EEA conditions are confirmed concurrently.[13]

Footnotes

  1. [8] See Walter [2014: §2] for a discussion.
  2. [9] For a discussion on this point, see Downes [2010]. For a brief summary of Buller's position, see his [2005a].
  3. [10] This set of examples is taken from Tooby and Cosmides [1997].
  4. [11] Buller [2005a] summarizes the research data.
  5. [12] For a critique of Gould's criticisms, see Buller [2005a: §3].
  6. [13] Sell et al [2003] makes a similar point.

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