Modern evolutionary theory, also known as the modern synthesis, has lately become the subject of much criticism--and yet, David Merrell observes, its critics all too often display an incomplete understanding of the theory and its provenance. In this book, Merrell provides a lucid exposition and critique of the modern synthetic theory of evolution--its history, its present difficulties, and its future--from the perspective of ecological genetics. Based on observational and experimental data, in natural populations of plants and animals studied in the field and in the laboratory, this perspective unravels the hidden and often poorly founded assumptions underlying some of the more troublesome controversies in evolutionary biology today.

Evolution, Merrell suggests, occurs through many mechanisms, and this pluralism informs his approach to evolutionary problems, which usually have been discussed in extreme, generally unjustifiable dichotomies. Thus, although much of evolution, in accordance with the Darwinian model, is slow and gradual, Merrell makes the case for rapid, even instantaneous large change as well. He also demonstrates the importance of genes of major effect, especially dominant genes, in bringing about evolutionary change, contrary to the widely held belief that such change only results from the accumulation of numerous genes of small effect. Using these concepts, Merrell interprets the evolution of industrial melanism, DDT resistance, and mimicry.

In the treatment of the nature and origins of species, Merrell proposes an “adaptive seascape” to replace Sewall Wright’s well-known “”adaptive landscape” as a metaphor for the adaptive surface, where the physical and biological environment is constantly changing. Expert yet accessible, Merrell’s depiction of this seascape will clarify the state of evolutionary theory both for specialists and for general readers with an interest in science.