Niche Markets

T his book, the latest in the excellent Monographs in Population Biology series from Princeton University Press, is a work of advocacy in which the authors argue that evolutionary theory is incomplete and that, in consequence, we are failing fully to understand phenomena as disparate as ecosystem development and the interplay of genes and culture in shaping human evolution. What we are missing, they argue, is an appreciation of niche construction, the process by which an organism modifi es the abiotic and biotic environment in which it is subject to natural selection. The authors' major assertion is that the importance of niche construction is so great that it should be regarded " after natural selection, as a second major participant in evolution " and that it is " not just an important addition to evolutionary theory " but " requires a reformulation of evolutionary theory ". Bold claims indeed. After introducing the conceptual framework Odling-Smee et al. set out a series of arguments to support this position, the fi rst of these being the empirical case for the existence of niche construction. Niche construction, as broadly interpreted here, is everywhere. Animals build nests, burrows, and protective cases and so alter the environment they experience in a way that may select for further adaptations. The changes caused by some animal species, such as beavers and earthworms, are of a suffi cient magnitude that the environment experienced by a host of other species is affected. Many plant species also modify the environment they experience by generating organic litter; infl uencing hydrological and biogeochemical cycles; affecting temperature, humidity, and light regimes; and, over the longer term, determining the make up of the atmosphere. Decomposer and chemoautotrophic microorganisms similarly infl uence biogeochemical transformations, while parasitic species can manipulate the behaviour and internal environment of the hosts they infect. Perhaps less obvious examples of niche construction are the many types of migration and cultural evolution that, like physical transformations, cause the organism's descendants to experience a different selective environment. After this broad, accessible survey, the authors change key rather abruptly and explore two-locus, frequency-dependent population genetics. The novelty here is that selection on one locus depends on the history of gene frequencies at the other, " niche construction " , locus. In an extension, gene frequencies at one locus affect an environmental variable with its own dynamics that in turn infl uences the second locus. …