Evolution__3rd_Edition

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Any theory of life has to explain
adaptation
CHAPTER 3 / The Evidence for Evolution 67
chapter in mind. How, for example, could we explain the molecular clock (Section 7.3,
p. 164) if species have independent origins? Or the difficulties of deciding whether
closely related forms are different species (Chapter 13)? Or the unique branching pattern
of chromosomal inversions in the Hawaiian fruitflies (Section 15.14, p. 463)? Or
the way new species of Hawaiian fruitflies tend to be most closely related to species on
neighboring islands (Section 17.6, p. 503).
3.13 Creationism offers no explanation of adaptation
Another powerful reason why evolutionary biologists reject creationism is that creationism
offers no explanation for adaptation. Living things are well designed, in innumerable
respects, for life in their natural environments. They have sensory systems to
find their way around, feeding systems to catch and digest food, and nervous systems to
coordinate their actions. The theory of evolution has a mechanical, scientific theory for
adaptation: natural selection. 3
Creationism, by contrast, has no explanation for adaptation. When each species
originated, it must have already been equipped with adaptations for life, because the
theory holds that species are fixed in form after their origin. An unabashedly religious
version of creationism would attribute the adaptiveness of living things to the genius of
God. However, even this does not actually explain the origin of the adaptation; it just
pushes the problem back one stage (Section 10.1, p. 256). In the scientific version of
creationism (see Figure 3.1c–e) we are concerned with here, supernatural events do
not take place, and we are left with no theory of adaptation at all. Without a theory of
adaptation, as Darwin realized (Section 1.3.2, p. 10), any theory of the origin of living
things is a non-starter.
3.14 Modern “scientific creationism” is scientifically
untenable
That life has evolved is one of the great discoveries in all the history of science, and it is
correspondingly interesting to know the arguments in favor of it. In modern evolutionary
biology, the question of whether evolution happened is no longer a topic of
research, because the question has been answered; but it is still controversial outside
science. Christian fundamentalists a some of them politically influential a in the USA
have supported various forms of creationism and have been trying since the 1920s,
3 The modern school of “intelligent design” creationism denies that natural selection explains adaptation a
opening up the possibility that some further (supernatural?) force may be operating. Intelligent design creationists
are not concerned to deny evolution, or to argue that species have separate origins and are fixed in
form. They are therefore not included in this chapter. In Chapter 10, we look at how well natural selection
explains adaptation.