|
A peer-reviewed
electronic journal published by the Institute
for Ethics and ISSN
1541-0099 20(1)
– June 2009 |
Book review:
Jerry A. Coyne’s Why Evolution Is True
Russell Blackford,
Editor-in-Chief, Journal
of Evolution and Technology
Journal of Evolution and Technology -
Vol. 20 Issue 1 – June 2009 - pgs 61-66
http://jetpress.org/v20/blackford.htm
Why Evolution Is True. By Jerry
A. Coyne. Viking,
ISBN: 978 0 670 02053 9 (all page
references to this edition)
Jerry
A. Coyne is a professor at the
Life on earth evolved gradually beginning with one primitive species –
perhaps a self-replicating molecule – that lived more than 3.5 billion years ago;
it then branched out over time, throwing off many new and diverse species; and
the mechanism for most (but not all) of evolutionary change is natural
selection. (3.)
This
breaks down into six components: the fact of evolution, in the sense of genetic
change over time; the idea of gradualism, of changes taking place over many
generations (although sometimes they come about relatively quickly, depending
on the evolutionary pressures operating); the phenomenon of speciation, whereby
new species split off from existing lineages; the common ancestry of different
species, since new species, which can be thought of as twigs on the developing
branches of life, can be traced back to a common branch, and ultimately to an
original ancestor; the mechanism of natural selection, whereby different
combinations of genes are reproduced more successfully than others as a result
of the different abilities of individual organisms to survive and reproduce in
a shared environment; and, finally, the presence of some processes, in addition
to natural selection, that contribute to evolutionary change (the most
important being what is known as “genetic drift”).
When
Coyne argues that “evolution is true,” he means,
first, that the central propositions of evolutionary theory – relating to these
six components – are all true. Furthermore, they should be accepted as true, as indeed they are in mainstream science, because
of the increasingly decisive evidence, from many lines of inquiry, that has
become available.
Although
the word “theory” is used by evolutionary biologists, this does not mean that the
evolutionary account of life's diversity is a mere speculation or conjecture:
as used by scientists, the word denotes “a
well-thought-out group of propositions to explain facts about the real world” (15). A point can arrive
where such a body of propositions has been so thoroughly tested, and so
overwhelmingly supported by evidence, that it is not just a theory (in the
sense just defined), but should also be acknowledged as a set of facts. In
principle, any such group of propositions could be falsified by new data, so
the propositions of science are accepted provisionally. But in some cases, as
with the heliocentric description of local astronomical bodies and their orbits,
it is vanishingly unlikely that the main propositions will ever be falsified.
Coyne’s central claim is that the main propositions of modern
Darwinian theory have graduated to “facthood” in this sense.
Coyne's
presentation of the evidence is fascinating and ultimately overwhelming. He produces
information from fields as diverse as embryology, biogeography, the fossil
record itself, the presence of vestigial structures in modern organisms, and
the presence in nature of suboptimal “designs,” in order to
demonstrate that organisms have evolved and that natural selection is
responsible for the vast diversity of apparent design. Evolutionary theory has
made huge numbers of successful predictions, explained data that would not
otherwise make sense (“retrodictions”), and never been falsified by anomalous observations
(there are no human fossils in Cretaceous rock strata, for example, or anything
like J.B.S. Haldane’s famous example of fossil rabbits in the Precambrian).
The
great strength of Why Evolutions Is True
lies in Coyne’s ability to assemble evidence from all these lines of inquiry,
and to demonstrate how the chains of inference converge. He shows convincingly
why no serious biologist doubts the main propositions of modern evolutionary
theory, such as the claims that organisms evolved over time, that lineages
split into different species, and that “natural selection is the main engine of
adaptation”
(223). Although the field of evolutionary biology is a vibrant one, and its
professional journals contain much discussion of the details of the process,
the main propositions are entirely uncontroversial within science, essentially
because they are supported so powerfully by huge amounts of converging data.
There
is no scientific controversy about
the status of modern evolutionary theory, but there is obviously a social
controversy, in that many individuals reject the theory, and there are
concerted efforts by well-resourced organizations, such as
In
the final chapter of Why Evolution Is
True, Coyne examines the motivations that may underlie resistance to the
theory of evolution. Why is it that someone of ordinary, or greater,
intelligence can be confronted with the convincing evidence of evolution,
understand it, but still not accept the main propositions that it supports?
Perhaps surprisingly, Coyne does not emphasize that the processes and the timeline
of evolution totally contradict fundamentalist Christian positions that include
the idea of Young Earth Creationism.
For
adherents of such positions, the age of the Earth and the specific creation of each
kind of living thing (especially, but not only, of human beings) are not merely
add-ons. It is not as if these ideas can be discarded, or seriously modified,
to accommodate the discoveries of science, while preserving an essential core
of spiritual doctrines. Rather, they are elements of an encyclopedic and closely-integrated
theological system that also includes a literal Fall from grace at an
identifiable time; the historical introduction of sin and corruption into the
world; Jesus Christ’s sacrificial atonement for sin; and an ultimate victory of
God over Satan. This cosmic victory will culminate in a fiery cleansing of all
creation – in effect, a new beginning. Such a belief system cannot lightly
accept modifications to its claims about the world, in space and time. As long
as this kind of Christian theology retains large numbers of adherents, there
will be many people who are strongly motivated to reject evolutionary theory rather
abandon their integrated religious worldview. For such people, even the shift
to some kind of “theistic evolution” is likely to be enormously painful,
and perhaps no more appealing than abandoning Christianity altogether.
Still,
many other areas of science – geology and astrophysics for a start – also
contradict Young Earth Creationism and its associated system of doctrine. Yet
these cause nothing like the same anxiety as modern evolutionary biology. So
perhaps Coyne is right to emphasise more general concerns, rather than those
specific to Christian fundamentalism. He suggests that many people require more
than evidence for the evolution of
life because they fear its consequences:
for these people, who are not all Young Earth Creationists or anything of the
sort, “evolution raises such profound questions of purpose, morality, and
meaning that they just can’t accept it, no matter how much evidence they see” (224). These well-intentioned
people are concerned about what follows, logically and psychologically, if
evolution is true.
To
be honest, I am tempted to give short shrift to such concerns. Evidence is
evidence. If the central propositions of modern evolutionary theory are
overwhelmingly supported by the evidence, that is that. Or so I am inclined to
say. We then need to work out the implications, rather than imagining that the
implications can control whether or not the theory is true. If some of the
implications appear to be unpalatable, it is irrational or intellectually
dishonest to allow that to decide what to believe. We should, rather, bite the
bullet and accept the genuine implications of the theory, whatever they might
turn out to be.
Perhaps
fortunately, Coyne takes a more gentle approach. He expresses sympathy with the
widespread fear that recognition of the truth of evolutionary theory could
dissolve whatever constraints stop us from acting in selfish and unscrupulous
ways. If we are essentially beasts, so the thought goes, why not give full rein
to the beast within? What logical basis might there be to control our most
destructive impulses?
Obviously,
these questions could provide the theme for an entire book, or for many books.
Coyne’s answer is that we are not “marionettes dancing on the strings of
evolution”
(230). Some of our behaviors may be genetically encoded, but our genes can be
expressed in many ways under many different circumstances. Though there is much
human selfishness and cruelty, there is also much kindness and altruism –
the choices are ours to make, and it is clear that our genetic heritage does
not take a form that traps us into so-called “beastly” behaviors. Indeed, as Coyne also
points out, we have been able to make a degree of moral progress during
recorded history, increasingly ruling out barbaric activities such as human
sacrifice and gladiatorial combat, while expanding our circles of sympathy and
consideration. This kind of progress is not caused by our genes, at least not
in any simple way, but they clearly do not prevent it. Thus it is simply a
misconception to think that accepting the truth of evolution will “somehow
sunder our society, wreck our morality, impel us to act like beasts, and spawn
a new generation of Hitlers and Stalins” (238).
I
agree entirely with this analysis as far as it goes, but there is another point
to be made, and it’s one that individuals who are wary of evolutionary theory
might well find less palatable. While it is consistent with Coyne’s approach,
it really belongs to another book and Coyne can surely be excused for not
mentioning it. Still, it is worth a brief discussion in a journal such as this.
The point is that a morality grounded in modern, scientific understandings of
the world and our place in it will not
be entirely the same as the old, familiar moral teachings, handed down through
religious and cultural traditions. Thus, if some opponents of evolutionary
theory – and, beyond it, of a naturalistic and materialist understanding of the
world – lament that their morality
cannot be preserved, in its entirety, they are probably right. From the
perspective of philosophical naturalism and materialism, much of the old
morality really can’t be supported. What has to be added, however, is that this
is not a bad thing.
The
old morality, closely associated with Christianity, with its long tradition of shame
about sex and the body, its hard-line advocacy of human exceptionalism (including a
specifically human “dignity”), and its glorification of piety, self-abnegation, and
asceticism, simply lacks rational support. Admittedly, much thinking remains to
be done about what the social institution of morality is for, and hence what form it should take: which deontic constraints
should we accept, or which virtues should we aspire to, and why? However, it is
unlikely that any rational approach will enable the old morality to be
reconstructed, unchanged. Indeed, it is already under challenge, and has been
for several decades.
As
a first approximation, morality serves such purposes as enhancing individual
flourishing, contributing to social survival, and ameliorating the suffering in
the world. Nothing about evolutionary theory requires us to cease valuing those
kinds of goals. However, a moral system aimed at goals such as these may have
little room for supposed virtues such as chastity or piety, or for traditional
proscriptions of various more-or-less harmless pleasures. A rationally-revised
morality is likely to have little to say against (for example) abortion,
stem-cell research, same-sex marriage, or technologies of assisted reproduction
and human enhancement. To be blunt about it, much of the old morality's content
is miserable and irrational, when viewed against various purposes that can
plausibly be assigned to morality itself. If acceptance of evolutionary theory
and a naturalistic worldview helps us to understand this, we ought to welcome
it, not stick our heads in the sands of tradition.
This,
however, takes me far from Jerry Coyne’s wonderful book, since its author does
not adopt anything like such a radical line, whether or not he might sympathize
with it. His achievement is a comprehensive and truly compelling synthesis of
the evidence in support of sound, established science. If you care passionately
about science and its advancement, and you’re looking for a book that explains the
case for evolution with vigor, verve, elegance, and clarity, Why Evolution Is True belongs on your
bookshelf.