Extended phenotype

The extended phenotype is the concept, developed by Richard Dawkins, that genes can influence traits beyond the organism's body. A beaver's dam, a bird's nest, a cuckoo's manipulation of its host — these are not phenotypic traits of the organism in the traditional sense, but they are products of the organism's genes, and they are subject to the same selective pressures as bodily traits. The extended phenotype extends the reach of the gene beyond the organism's skin, into the environment that the organism modifies.

The concept has profound implications for how we think about the unit of selection. If genes can influence the environment, then the environment is not a fixed selective pressure but a dynamic product of the evolutionary process itself. Organisms do not just adapt to environments; they construct environments that then feed back to select on future generations. This is the basis of niche construction theory, which treats environmental modification as an evolutionary force in its own right. The extended phenotype also connects to questions about technology and culture: are human tools, languages, and institutions extended phenotypes of the genes that build human brains? See also Evolutionary theory, natural selection, and fitness landscape.