Why Darwin Matters (3 page)

But whatever happens in these politically charged skirmishes, truth in science is not determined by the
vox populi
. It does not matter whether 99 percent or just 1 percent of the public (or politicians)
accepts a scientific theory—the theory stands or falls on the evidence, and there are few theories in science that are more robust than the theory of evolution. It took me a long time to realize this fact, for I began my career as a creationist. Saying this today almost feels like confessing a murder.

Like confessing a murder
. That is precisely how I felt when I realized that my creationist beliefs were wrong and that evolution actually happened. I became a creationist shortly after I became a born-again evangelical Christian in high school in 1971 and argued the creationist case through graduate school in 1977.
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The evangelical movement was gathering momentum in the 1970s, and one of the central dogmas I took from it was that the biblical story of creation was to be taken literally; ergo, the theory of evolution had to be wrong.

Knowing next to nothing about evolution other than what I gleaned from reading creationist literature, I absorbed the arguments against the theory and practiced them on my undergraduate science and philosophy teachers. At Glendale College, which I attended for the first two years for general education requirements, I honed my debating skills as my creationist arguments were met with firm evolutionist counterarguments. At Pepperdine University, a Church of Christ institution where I finished my undergraduate degree, evolution was a nonentity as I witnessed for Christ and studied the theological underpinnings of the Christian faith. When I arrived at Pepperdine, in fact, I considered theology as a profession, but when I discovered that a doctorate required proficiency in Hebrew, Greek, Latin, and Aramaic, and knowing that foreign languages were not my strong suit (I struggled through two years of high school Spanish), I switched to psychology and mastered one of the languages of science: statistics. By the time I matriculated at
California State University at Fullerton for graduate training in experimental psychology, I was ensconced in the methods of science.

In science, the solutions to problems are based on established parameters to determine whether a hypothesis is probably right or definitely wrong. Statistics allow researchers to identify an event as likely to happen 99.99 percent of the time (rejecting the null hypothesis) or as insignificant. Instead of the rhetoric and disputation of theology, there are the logic and probabilities of science. What a difference this shift in thinking makes. In graduate school, I took a bevy of courses in research methods and statistics, and for recreation I signed up for a Tuesday evening course in evolution, just to see firsthand what had us creationists up in arms. The course was taught by an eccentrically charismatic biologist named Bayard Brattstrom, who from 7 to 10
P.M.
regaled his class with breathtaking discoveries from the science of evolutionary biology, and who from 10
P.M.
to closing time at the 301 Club just down the street held forth on science and religion, Darwin and Genesis, and all manner of related topics, accompanied by appropriate libations.

The scales fell from my eyes! It turned out that the creationist literature I was reading presented a Darwinian cardboard cutout that a child could knock down. (For example, if humans come from apes, why are apes still around? Of course, we didn’t evolve from modern apes; apes and humans evolved from a common ancestor who lived nearly seven million years ago.) What I discovered was that the preponderance of evidence from numerous converging lines of scientific inquiry—geology, paleontology, zoology, botany, comparative anatomy, molecular biology, population genetics, biogeography, embryology, and others—all independently converge to the same conclusion: Evolution happened.
Why Darwin Matters
is about how we know evolution happened, in the context of the challenges to evolution mounted by twenty-first-century creationists and Intelligent Design theorists.

Why does evolution matter?
The influence of the theory of evolution on the general culture is so pervasive it can be summed up in a single observation:
We live in the age of Darwin
. Arguably the most culturally jarring theory in history, the theory of natural selection gave rise to the Darwinian revolution that changed both science and culture in ways immeasurable. On the scientific level, the static creationist model of species as fixed types was replaced with a fluid evolutionary model of species as ever-changing entities. The repercussions of this finding were, and are, astounding. The theory of top-down intelligent design of all life by or through a supernatural power was replaced with the theory of bottom-up natural design through natural forces. The anthropocentric view of humans as special creations placed by a divine hand above all others was replaced with the view of humans as just another animal species. The view of life and the cosmos as having direction and purpose from above was replaced with the view of the world as the product of the necessitating laws of nature and the contingent events of history. The view that human nature is infinitely malleable and primarily good was replaced with a view of human nature in which we are finitely restricted by our genes and are both good and evil.
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Darwin matters not only because his theory changed the world and reconfigured our position in nature, but because he launched a new and profound understanding of biology and science that has served future generations. Of the three intellectual giants of that epoch—Darwin, Marx, and Freud—only Darwin is still relevant for the simple reason that his theory was right, and the scientific evidence continues to support and refine it. In the memorable observation by geneticist Theodosius Dobzhansky, “Nothing in biology makes sense except in the light of evolution.”
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The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth. As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever branching and beautiful ramifications.

—Charles Darwin,
On the Origin of Species
, 1859

The theory of evolution has been under attack since Charles Darwin first published
On the Origin of Species
in 1859. From the start, its critics have seized on the
theory
of evolution to try to undermine its facts. But all great works of science are written in support of some particular view. In 1861, shortly after he published his new theory, Darwin wrote a letter to his colleague, Henry Fawcett, who had just attended a special meeting of the British Association for the Advancement of Science during which Darwin’s book was debated. One of the naturalists had argued that
On the Origin of Species
was too theoretical, that Darwin should have just “put his facts before us and let them rest.” In response, Darwin reflected that science, to be of any service, required more than list-making; it needed larger ideas that could make sense of piles of data.
Otherwise, Darwin said, a geologist “might as well go into a gravelpit and count the pebbles and describe the colours.”
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Data without generalizations are useless; facts without explanatory principles are meaningless. A “theory” is not just someone’s opinion or a wild guess made by some scientist. A theory is a well-supported and well-tested generalization that explains a set of observations. Science without theory is useless.

The process of science is fueled by what I call
Darwin’s Dictum
, defined by Darwin himself in his letter to Fawcett: “all observation must be for or against some view if it is to be of any service.”

Darwin’s casual comment nearly a hundred and fifty years ago encapsulates a serious debate about the relative roles of data and theory, or observations and conclusions, in science.
²
In a science like evolution, in which inferences about the past must be made from scant data in the present, this debate has been exploded to encompass a fight between religion and science.

Most essentially,
evolution is a historical science
. Darwin valued above all else prediction and verification by subsequent observation. In an act of brilliant historical science, for example, Darwin correctly developed a theory of coral reef evolution years before he developed his theory of biological evolution. He had never seen a coral reef, but during the
Beagle
’s famous voyage to the Galápagos, he had studied the types of coral reefs Charles Lyell described in
Principles of Geology
. Darwin reasoned that the different examples of coral reefs did not represent different types, each of which needed a different causal explanation; rather, the different
examples represented different stages of development of coral reefs, for which only a single cause was needed. Darwin considered this a triumph of theory in driving scientific investigation: Theoretical prediction was followed by observational verification, whereby “I had therefore only to verify and extend my views by a careful examination of coral reefs.”
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In this case, the theory came first, then the data.

The publication of the
Origin of Species
triggered a roaring debate about the relative roles of data and theory in science. Darwin’s “bulldog” defender, Thomas Henry Huxley, erupted in a paroxysm against those who pontificated on science but had never practiced it themselves: “There cannot be a doubt that the method of inquiry which Mr. Darwin has adopted is not only rigorously in accord with the canons of scientific logic, but that it is the only adequate method,” Huxley wrote. Those “critics exclusively trained in classics or in mathematics, who have never determined a scientific fact in their lives by induction from experiment or observation, prate learnedly about Mr. Darwin’s method,” he bellowed, “which is not inductive enough, not Baconian enough, forsooth for them.”
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Darwin insisted that theory comes to and from the facts, not from political or philosophical beliefs, whether from God or the godfather of scientific empiricism. It is a point he voiced succinctly in his cautions to a young scientist. The facts speak for themselves, he said, advising “the advantage, at present, of being very sparing in introducing theory in your papers; let theory guide your observations, but till your reputation is well established, be sparing of publishing theory. It makes persons doubt your observations.”
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Once Darwin’s reputation was well established, he published his book that so well demonstrated the power of theory. As he noted in his autobiography, “some of my critics have said, ‘Oh, he is a good
observer, but has no power of reasoning.’ I do not think that this can be true, for the
Origin of Species
is one long argument from the beginning to the end, and it has convinced not a few able men.”
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