ASEBL Journal – Volume 13 Issue 1, January 201 8
agent of design because it ties traits and thus DNA functionally to features of the envi-
ronment; (2) evolution is indeed a powerful source of explanation and challenges cer-
tain competing explanations, but leaves other sorts of explanation intact, although
placing them into a broader context; and (3) the results of evolution are amoral and we
must use other means to decide whether to embrace their effects on us or to fight
against them. Such is the general consensus.
Evolution certainly does have a random component, though it lies not in the engine of
natural selection so much as in the fuel of mutation. Still, to say that mutations are
random is too short a cut. Mutations can have very predictable and deterministic caus-
es, such as ultraviolet or other radiation and certain chemicals; they also occur through
simple mistakes in copying as DNA replicates, much as any machine will make errors
at a certain rate through processes that are at least somewhat understood. Moreover,
the degree of error-proneness of replication can itself evolve by natural selection.
What is meant by “random mutation” is not that there is a permanent inscrutability,
much less a mysterious lack of causal specificity, to mutations. Rather, the particular
instances of mutation are not guided by whether they are advantageous or not. A mu-
tation is not produced “in order to” achieve a specific effect. Mutation rate in general
can evolve by natural selection, but with some rather boring exceptions natural selec-
tion cannot favor the occurrence of a mutation with a particular advantageous effect;
thus mutation is random with respect to its effects in the game of life. In this same
sense the next card a dealer peels off is random, even though there were very specific
causes of its precise position in the deck. This sort of randomness is not the sort with
any metaphysical teeth. If any more important sort of randomness applies to evolu-
tion, it is not particular to evolution but is a matter for the physicists to discuss.
Evolution not only describes, but explains; and its explanations render certain others
defunct, as all scientific explanations do. This pill is always hard to swallow for some
who prefer certain falsified or obsolete explanations. The discovery by evolutionary
biology that the function of sweet colorful fruits hanging from plants is to achieve
dispersal of the plants’ offspring via hungry animals supersedes other explanations,
for instance that fruit is produced by plants to benefit animals because animals are
higher on the chain of being than plants. Evolutionary functional explanations tend to
have a striking, penetrative or trenchant quality. They explain “why” in a way that
pre-evolutionary folks typically thought (and think) possible only for metaphysical or
religious explanations. Still, we need not worry that such explanations are all-
consuming or eliminative of other sorts of explanation. We teach our students that
evolutionary function (adaptation), evolutionary history (phylogeny), organismal de-
velopment (ontogeny), and physiological processes are all separate sorts of biological
explanation that cannot possibly undermine each other but contribute to an integrated
understanding of “why” and “how” at different levels. And we can move from these
levels out of biology into chemistry and physics in one direction, and (for some traits
at least) into psychology and agency in another direction, and the rich mosaic of ex-
planation is maintained. Even if we had a complete neuroscience, for instance, a neu-
ral explanation would not answer us as effectively as a verbal agency-centered one if
we asked why a chess player moved the knight from G1 to F3. Agency is not even
directly accessible to science, and so it brings us into a novel sort of purposive expla-
nation that at most can be interdigitated with science rather than being replaced or
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