578 THE STRUCTURE OF EVOLUTIONARY THEORY
Many paeans to adaptation proceeded beyond mere claims about
omnipresence to assert optimalized excellence, or near organic perfection, as well.
Convictions about the exclusive power (as well as the range) of natural selection
emerge most clearly from such statements, as by Telford and Kennedy (1965, p. 3)
(Kennedy later became the president of Stanford University and editor of Science
magazine):
It is of profound importance for the nature of the organism that, due to
natural selection, the evolutionary changes in organisms have either moved
relentlessly in the direction of efficiency or have kept them attuned to a
changing environment... Evolutionary adaptation thus suggests an
extremely fine attunement between organism and environment. The
organism doesn't merely get along; its whole life mode has been tempered
and refined by the successful competition of generations of its ancestors
with a multitude of differing genotypes. Thus even in the finest details of
their organization, organisms are constructed and operate in a manner
which makes sense in terms of the way they make their living.From this assertion of omnipresence for adaptation in morphologies,
physiologies and behaviors of the moment, these texts then proceed to ascribe the
second great phenomenon of evolution—the production of diversity—to natural
selection as well. Simpson et al. (1957, p. 405) extend selection's scope to all
phenomena at all scales by writing: "The evolutionary process, viewed in broad
perspective, is characterized by two major features: it produces diversity among
living things, and it gives rise to their adaptation, their fitness to survive and
reproduce efficiently in the environments they inhabit. These two features are
interdependent: life's diversity is largely a diversity in adaptation."
Speciation, although replete with nonadaptive elements in Mayr's canonical
formulation, usually receives a textbook description as an even stronger
affirmation of natural selection (because the process now operates in two separated
lines, working its differential effects to produce just the right adaptations in both
distinct and varying environments). Nelson et al. entitling their section
"Speciation: The Results of Adaptation," write in summary (1967, p. 235):
"Natural selection operating on the variability present in the genotypes of
populations can cause better adaptation of organisms to their environment.
Coupled with reproductive isolation, these adaptations bring about speciation."
Jones and Gaudin (1977, p. 548) introduce their discussion of speciation with
a scenario of pure adaptation and extrapolation. (Their full text discusses other
mechanisms, including polyploidy—but note the pride of place awarded to
adaptation, and the argument that so separate and important a phenomenon as
geographic isolation only provides an impetus by setting new selection pressures in
a different environment):
The accumulation of adaptations can lead to the production of new species,
a process called speciation.... Suppose a population of gophers living