102 Evolution and the Fossil Record
bad, preserving and adding up all that is good; silently and insensibly working.” Some even
argued that all changes are adaptive in some way, even if we can’t detect how. To them, there
are no features of an organism unaffected by natural selection. Such views are often called
panselectionism.
Along with the reductionist attitude that organisms are nothing more than vessels
to carry their genes came the extrapolation that the tiny genetic and phenotypic changes
observed in fruit flies and lab rats were sufficient to explain all of evolution. This defines
all evolution as microevolution, the gradual and tiny changes that cause different wing veins
in a fruit fly or a slightly longer tail in a rat. From this, neo-Darwinism extrapolates all
larger evolutionary changes (macroevolution) as just microevolution writ large. These central
tenets—reductionism, panselectionism, extrapolationism, and gradualism—were central to
the neo-Darwinian orthodoxy of the 1940s and 1950s and are still followed by the majority
of evolutionary biologists today.
As we shall see later in this chapter, the evidence for microevolutionary change is abun-
dant throughout nature, and we see evolution in action all the time. Neo-Darwinian evo-
lutionary biology has had many great successes (detailed in all the textbooks), so there is
no reason to doubt that natural selection is the most important engine for evolution. But
is it the only factor involved? Is evolution truly reducible to changes in gene frequencies
through time?
Challenges to Neo-Darwinism
The variations detected by electrophoresis may be completely indifferent to the action
of natural selection. From the standpoint of natural selection they are neutral mutations.
—Richard Lewontin, The Genetic Basis of Evolutionary ChangeUnfinished Synthesis
When neo-Darwinism swept through the profession in the 1940s and 1950s, it achieved
almost a complete consensus. Many evolutionary biologists thought that the major problems
were all solved; only the details needed to be worked out. But it is not a good thing when a
field in science seems to have all the answers and is no longer questioning its assumptions.
A continuing critical attitude, new unsolved problems, and skepticism and controversy are
essential to the health of good science. If a science does not continue to test its ideas and
views all essential problems as solved, then it soon stagnates and dies.
Fortunately, the neo-Darwinian synthesis has been continually scrutinized and chal-
lenged by legitimate biological and paleontological data, so the field is rife with healthy con-
troversy. Most of these challenges only question some of the more extreme neo-Darwinian
tenets or argue that natural selection is not the only mechanism by which life evolves.
Despite the misleading misquotations of creationists, none of these ideas challenges the well-
established fact that life has evolved or that natural selection is an important (if not exclusive)
mechanism for evolution. For example, creationists frequently quote Stephen Jay Gould say-
ing that “neo-Darwinism is dead” and suggest that Gould does not believe in evolution! In
fact, Gould is arguing for the importance of non–neo-Darwinian mechanisms for evolution.
A typical Gould quote in context reads: