Commentary/Laland et al.: Niche construction or of acquired information, as convenient. Such switching between symbolically encoded information and phenotype is legitimate only where there is a tight correspondence between information and behaviour (Cronk 1995). Where this correspondence is weak, gene-culture methods might have to be developed further, for example, by introducing a coefficient into the models that represents the extent to which individuals with a particular combination of genes and acquired information are likely to express a particular behavioural phenotype.
Open Peer Commentary Commentary submitted by the qualified professional readership of this journal will be considered for publication in a later issue as Continuing Commentary on this article. Integrative overviews and syntheses are especially encouraged.
Gene-culture coevolution does not replace standard evolutionary theory Mauro Adenzato Centro di Scienza Cognitiva, Università di Torino, 10123 Turin, Italy.
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Abstract: Though the target article is not without fertile suggestions, at least two problems limit its overall validity: (1) the extended gene-culture coevolutionary framework is not an alternative to standard evolutionary theory; (2) the proposed model does not explain how much time is necessary for selective pressure to determine the stabilization of a new aspect of the genotype.
Laland, Odling-Smee & Feldman deserve credit for an original treatment of aspects of the relation between culture and biological evolution. That notwithstanding, their extended gene-culture coevolutionary framework cannot be considered an alternative to standard evolutionary theory, as the addition of the concept of niche construction to the model developed in previous works of CavalliSforza and Feldman (1981) and Boyd and Richerson (1985) is not sufficient for the proposed model to replace the standard approach to the study of evolution. The reason resides in the interactions between the processes of niche construction and natural selection. According to Laland et al., evolution consists of mutual and simultaneous processes of natural selection and niche construction (sect. 1.1, last para.). In reality, invoking a mechanism parallel to natural selection is redundant. To demonstrate this it is enough to consider three simple examples cited by the authors: migratory behavior (sect. 1.1, para. 2), the behavior of certain insects (such as ants and termites) capable of regulating the humidity and temperature of their nests (sect. 1.1, p. 3), and finally the behavior of earthworms, which changes both the structure and chemistry of the soil (sect. 1.1, para. 9). In all these cases (as in others cited in the target article), the reference to a process able to permit diverse species of animals to choose, modify, and create their own ecological niches is not mistaken; it is in fact useful as it allows the formulation of hypotheses about the adaptation of these species to their environment. But the process cannot be considered as an alternative, nor even as an adjunct to the standard mechanism of natural selection, for at least two reasons. First, because in cases such as migration or the regulatory behavior of ants and termites, the processes of niche construction do not counteract the pressures of selection but are rather its direct expression. To fail to consider this point adequately is to risk inserting a teleological dimension into the explanation of evolutionary phenomena, as if to say that because it is cold at certain times of the year, or because
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the interior temperature of the nest may rise too high, organisms evolve behaviors to counteract these pressures. In reality, the causal relationship is the inverse; thanks to natural selection, those ancestral organisms that as an effect of random genetic mutation had traits that rendered them capable of particular regulatory behaviors were favourably selected. Inasmuch as it is obvious that Laland et al. do not intend to present a teleological explanation of evolutionary processes, some passages of their work can lead to misunderstandings in this sense. The second reason to doubt that niche construction and natural selection are two alternative processes can be derived from the example of the earthworms mentioned above. The very fact that some phenotypical characteristics of earthworms have coevolved in an environment that at least partially “niche constructed” by their ancestors, demonstrates that niche construction is simply one of the ways in which natural selection manifests itself. Niche construction and natural selection are therefore not alternative or parallel processes; the former is simply one of the expressions of the latter. In substance, if Laland et al. deserve credit for having investigated the role played in evolution by selective pressures other than purely physical ones such as temperature, humidity, the availability of food, it seems harder to share the idea of assigning the body of selective pressures responsible for niche construction to a process distinct from natural selection. These considerations are even more convincing when the authors refer to more complex examples of niche construction, such as those based on ontogenetic and cultural processes. Even in this case their model cannot be substituted for the standard one, although it does, in a certain sense, provide an amplification. Furthermore, the very treatment of ontogenetic and cultural aspects puts into greater relief another problem in the work of Laland et al. regarding the time necessary for selective pressure to determine the appearance and stabilization of a new aspect of the genotype. In some sections the authors speak of “enough generations” (sect. 1), and “sufficient generations” (sect 1.1) for an environmental modification due to niche construction to become a selective pressure that can influence a species. There have been similar difficulties in other theoretical frameworks such as the gene-culture coevolutionary theory of Lumsden and Wilson (1981; see also BBS multiple book review: Lumsden & Wilson’s “Genes, Mind, and Culture” BBS 5(1) 1982). The framework of evolutionary psychology today seems to deal better than any other with the problem of the time necessary for selective pressure to permit the appearance and stabilization of a new mechanism. Evolutionary psychology (Barkow et al. 1992) resolves the problem by examining the selective pressures recurrently encountered over the last two million years (at least) by individuals of genus Homo in their environment of evolutionary adaptedness. By making reference to the type of social organization that has characterized the evolutionary history of genus Homo, it is possible, for example, to develop a hypothesis regarding such a particularly complex behavior as deception (Adenzato & Ardito 1999). Until the modern gene-culture coevolutionary theory is able to quantify closely enough the time needed for an environmental change from niche construction to effect a stable modification in the nature of an organism, we must acknowledge the fact that a new trait evolved in response to that environmental change can quickly disappear, following a sudden cessation of the selective pressure. This is the same as asking whether the persistence of an environmental change due to niche construction for some generations ensures that there will be a stable modification in the nature of an organism. ACKNOWLEDGMENT This work has been supported by the Ministero dell’ Università e delle Ricezca Scientifica e Tecnologica of Italy (60%, 1997, The development of pragmatic competence).
