8 - Impact of developmental processes on evolution

Summary

For many years the debate about the role of an individual's development and its impact on its descendants was sharply polarised. The impact was seen as substantial by some and as non-existent by others. The position that knowledge of development was irrelevant to the understanding of evolution was forcefully set out by the advocates of the Modern Synthesis, as we mentioned in Chapter 1. John Maynard Smith (1982) suggested that the widespread acceptance of August Weismann's (1885) doctrine of the separation of the germline from the soma was crucial to this line of thought. It led to the view that genetics, and hence evolution, could be understood without understanding development. These views were, until recently, dominant and involved the fusion of Darwin's mechanism for natural selection with Mendelian genetics. Briefly put, genes influence the characteristics of the individual; if individuals differ because of differences in their genes, some may be better able to survive and reproduce than others and, as a consequence, their genes are perpetuated.

The extreme alternative to the Modern Synthesis is a caricature of Lamarck's views about biological evolution and inheritance. If a blacksmith develops strong arms as a result of his work, his children will have stronger arms than would have been the case if their father had been an office worker. This view has been ridiculed by essentially all contemporary biologists.