Jeffrey S. Turner

Phenotype, whether conventional or extended, is defined as a reflectionof an underlying genotype. Adaptation and the natural selection thatfollows from it depends upon a progressively harmonious fit betweenphenotype and environment. There is in Richard Dawkins' notion ofthe extended phenotype a paradox that seems to undercut conventionalviews of adaptation, natural selection and adaptation. In a nutshell, ifthe phenotype includes an organism's environment, how then can theorganism adapt to itself? The paradox is resolvable through aphysiological, as opposed to a genetic, theory of natural selection andadaptation.

In modern evolutionary theory, selection acts on particular genes and assemblages of genes that operate through phenotypes expressed in environments. This view, however, overlooks the fact that organisms often alter their environments in pursuit of fitness needs and thus modify some environmental selection pressures. Niche construction theory introduces a reciprocal causal process that modifies natural selection relative to three general kinds of environmental components: abiota, biota (other organisms), and artifacts. The ways in which niche-constructing organisms can construct or modify the components differ. Modification of abiota, for example, may have different consequences from the construction of artifacts. Some changes in abiota may simply be caused by the by-products of metabolisms and activities of organisms. Alternatively, artifacts may be “extended phenotypes” that demonstrate obvious prior “design” and “construction” by organisms in the service of fitness needs. Nevertheless, adaptation should always account for the reciprocity between constructed niches and the living agents that construct them. Looking to well-adapted nature for inspiration for human-built artifacts must account for this reciprocity between phenotype and constructed environment as well as the novel features of human architecture, including frank intentionality of design and novel culturally acquired knowledge.