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Sewall Wright's 1932 adaptive landscape diagram is the most influential visual heuristic in evolutionary biology. Yet, the diagram has met with criticism from biologists and philosophers since its origination. This chapter states that the diagram is a valuable evaluation heuristic for assessing the dynamical behaviour of population genetics models. Although Wright's particular use of it is of dubious value, other biologists have established the diagram's positive heuristic value for evaluating dynamical behaviour. This chapter surveys some of the most influential biological and philosophical work considering the role of the adaptive landscape in evolutionary biology. The chapter builds on a distinction between models, metaphors, and diagrams to make a case for why adaptive landscapes as diagrams have heuristic value for evolutionary biologists.

This chapter traces the origins and conceptual lineages of the adaptive landscape concept and its representations. While Armand Janet's 1895 concept arguably marks the origin of the adaptive landscape concept and even its graphic representation, Janet's concept had very limited impact when compared to Sewall Wright's concept from 1932. As part of his effort to reconcile Mendelian genetics and Darwinian evolution in his shifting balance theory, Wright offered the metaphor of the adaptive landscape and its topographic representation as a way of depicting the effect of variations in population size, migration, and the strength of selection. Wright's genetic version of the adaptive landscape inspired other versions of the adaptive landscape based on phenotypic changes and on molecular changes. As a result, the history of the adaptive landscape is described in terms of three lineages based on the material basis of the adaptive landscape: the genetic landscape, the phenotypic landscape, and the molecular landscape.

Sewall Wright’s classic Adaptive Landscape has been a highly successful metaphor and scientific concept in evolutionary biology. It has influenced many different research subdisciplines in evolutionary biology and inspired generations of researchers, even though it has also sparked deep scientific and philosophical controversies. Among such subdisciplines are population genetics, evolutionary ecology, quantitative genetics, experimental evolution, conservation biology, speciation and macroevolutionary dynamics, mimicry, saltational evolution, behavioural ecology, molecular biology, protein networks, and theoretical studies on development.

Darwin's separation between adaptedness and existence entered into modern evolutionary theory at its root, in the population genetics work of Sewall Wright and J. B. S. Haldane. This chapter shows how the teleological aspect of Darwin's theory was translated into the mathematical language of population genetics, particularly by Sewall Wright. This teleology is exemplified by Wright's metaphor of the adaptive landscape; it is absent from R. A. Fisher's fundamental theorem. The chapter also examines the debate over genetic load, showing that the separation of adaptedness from existence is transferred to the mathematical theory most directly in the form of confusion between absolute and relative fitness.

The adaptive landscape metaphor is one of the most persistent in evolutionary biology, and has generated much theoretical debate (if far less empirical investigation). This chapter briefly traces the history of the concept since its introduction by Sewall Wright in the 1930s. It then distinguishes four types of landscapes pertinent to evolutionary theory: fitness landscapes, adaptive landscapes, fitness surfaces, and morphospaces. These are more or less loosely related to each other, and sometimes the relationship is complex and difficult to explore empirically. The chapter argues that some versions of the landscape metaphor have lost their utility and should be replaced by more sophisticated metaphors, or abandoned altogether. It suggests that — somewhat surprisingly — the most useful type of landscape may turn out to be the morphospace, a concept that allows for a productive bridge between theoretical analyses and empirical results, especially in fields such as palaeontology and evolutionary developmental biology. In particular, the chapter discusses examples from the paleontological literature that constitute instances of truly (and stunningly) predictive theoretical analysis in what is often considered an entirely descriptive historical science.

This chapter contains a discussion of the ecological and the genetic basis for Sewall Wright’s Shifting Balance Theory. It also relays discussions of the author with Wright about how to experimentally test his theory using flour beetle metapopulations. The experimental design used by Wade and C. J. Goodnight to test Wright’s theory and to estimate realized group heritabilities is illustrated. The surprizing finding that interdemic selection every-other generation produced a larger response than selection at every generation was interpreted as evidence of non-additive effects on population mean fitness.

Fitness maximization, or optimization, is a controversial idea in evolutionary biology. One classical formulation of this idea is that natural selection will tend to push a population up a peak in an adaptive landscape, as Sewall Wright first proposed. However, the hill-climbing property only obtains under particular conditions, and even then the ascent is not usually by the steepest route; this shows why it is misleading to assimilate the process of natural selection to a process of goal-directed choice. A different formulation of the idea of fitness-maximization is R. A. Fisher’s ‘fundamental theorem of natural selection’. However, the theorem points only to a weak sense in which selection is an optimizing process, for it requires that ‘environmental constancy’ be understood in a highly specific way. It does not vindicate the claim that natural selection has an intrinsic tendency to produce adaptation.