Evolution, Genetic Variability and the Environment

Abstract

The main tenet of Lamarckism remembered today is ‘the inheritance of acquired characters’, the phrase and law on which so much criticism rightly falls. Lamarckism united environment, genotype and phenotype, with primacy given to the environment. Rejection of Lamarckism and its implications separated the phenotype from the genotype and led to an almost total neglect of the environment as a factor in the production of change. Yet, organisms do adapt to environments during their lifetimes and although such adaptation is not inherited as such, the capacity to respond to the environment is heritable, as amply demonstrated in the last chapter. This capability, coupled with developmental plasticity and pre-adaptation, can lead to long-term evolutionary change. The arguments for epigenetic control of ontogeny (Part Two) and for developmental change in phylogeny (Part Three), were, in part, arguments for inclusion of ‘environmental’ control. The need to bring the environment back into discussions of genotypephenotype interactions is the topic of this chapter.

‘A major gap in our knowledge of internal causes in evolutionary mechanisms is their environmental context. In addition to the genetic origins of particular changes, what are the ecological factors? How are the internal and external environments related? … It also brings us to new questions about the inter-relationships of internal processes acting within development and externalist processes acting within populations. To what extent can selection reinforce the causation of change in developmental mechanisms?’ Thomson, 1986, p. 232