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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.
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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.
[email protected]
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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BEHAVIORAL AND BRAIN SCIENCES (2000) 23:1
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).