The Nature of Science 19apart. Several statistical analyses showed that there was no correlation at all; many of the
“extinction peaks” turned out not to be real or were millions of years too early or too late
to have been part of a regular astronomical cycle; and most were found not to have any
evidence of an extraterrestrial impact (see Prothero 1994a). Sepkoski (1989) made one last
valiant attempt to answer the critics and salvage the hypothesis, but Stanley (1990) gave a
much simpler explanation that better fits the data. In a truly gigantic mass extinction, there
are so few survivors living in the aftermath that the world is populated with opportunistic
“weed-like” species, ecological generalists that thrive in disturbed habitats with little or no
competition. Eventually, however, more complicated, specialized species and ecosystems
re-evolve and replace those that the mass extinction wiped out. It apparently takes about
20 million years or more for the planet to recover from a mass extinction and for all these
extinction-prone specialized species to evolve again. If some great disturbance happens only
a million years after a mass extinction, you would never see it, because there are few species
that are vulnerable to extinction. Only after enough time has passed do they evolve; this is
why the mass extinctions described by Raup and Sepkoski were spaced roughly 20–30 million
years apart, but no shorter.
- The World Is Not Black and White, but Shades of Gray
Also known as the “either-or” fallacy or the “false dilemma,” this is a common strategy in
which the arguer tries to present his or her case as a choice between one extreme and another.
This thought is reflected in the famous slogans “If you are not with us, you’re agin’ us” or “If
you are not part of the solution, you are part of the problem.” By dichotomizing their world
into only two positions, they create the false dilemma that evidence against one point of view
is evidence for another. This is the principal tactic of the creationists, who try to create the
false dilemma that they are the only true Christians, and anyone who does not agree with
them is an atheist.
But as mature adults know, most matters in life are not black and white but shades
of gray. Arguments against one position do not necessarily support the opposite position.
Creationism is not the only form of Christianity, and there are many Christian evolution-
ists. Indeed, there is a wide spectrum of beliefs, from literalistic young-earth creationists
to “day-age creationists,” who allow the “days” in Genesis to be geologic ages, to theistic
evolutionists and so on. As in any other aspect of life, there are many possible answers or
possible viewpoints, and we should not be suckered into the dilemma of believing that there
are only two alternatives.
A corollary of the “false dilemma” principle is what Shermer (1997:52) calls “the unex-
plained is not inexplicable.” Many people (such as the “intelligent design” creationists dis-
cussed in the next chapter) argue that if they cannot explain something, then nobody can. This
is not only arrogant, but it is built on the false “either-or” premise that if no explanation is
currently available, then the phenomenon will never be explained. But just because we don’t
have an explanation now doesn’t mean that we won’t find one someday. In the meantime,
we do science and knowledge a disservice by defaulting to supernatural explanations sim-
ply because we still have an unsolved mystery in front of us. Scientists are used to dealing
with uncertainty and realizing that their answers are tentative and subject to change, but the
general public seems to prefer the comfort of any kind of answer (even if it is wrong) to the
insecurity of living with the uncertain and unknown. As H. L. Mencken put it, “For every
problem, there is a solution that is simple, neat, and wrong.”