Why Darwin Matters (6 page)

8.
Goose bumps
. Our body hair ancestry can also be inferred from the fact that we retain the ability of our ancestors to puff up their fur for heat insulation, or as a threat gesture to potential predators. Erector pili—“goose bumps”—are a telltale sign of our evolutionary ancestry.

9.
Extrinsic ear muscles
. If you can wiggle your ears you can thank our primate ancestors, who evolved the ability to move their ears independently of their heads as a more efficient means of discriminating precise sound directionality and location.

10.
Third eyelid
. Many animals have a nictitating membrane that covers the eye for added protection; we retain this “third eyelid” in the corner of our eye as a tiny fold of flesh.

Evolutionary scientists can provide dozens more examples of vestigial structures—let alone examples of how we know evolution happened from all of these other various lines of historical evidence. Yet as a science, evolution depends primarily on the ability to test a hypothesis. How can we ever test an evolutionary hypothesis if we cannot go into a lab and create a new species naturally?

I once had the opportunity to help dig up a dinosaur with Jack Horner, the curator of paleontology at the Museum of the Rockies in Bozeman, Montana. As Horner explains in his book
Digging Dinosaurs
, “paleontology is not an experimental science; it’s an historical science. This means that paleontologists are seldom able to test their hypotheses by laboratory experiments, but they can still test them.”
²⁷
Horner discusses this process of historical science at the famous dig in which he exposed the first dinosaur eggs ever
found in North America. The initial stage of the dig was “getting the fossils out of the ground.” Unsheathing the bones from the overlying and surrounding stone is backbreaking work. As you move from jackhammers and pickaxes to dental tools and small brushes, historical interpretation accelerates as a function of the rate of bone unearthed. Then, in the second phase of a dig, he gets “to look at the fossils, study them, make hypotheses based on what we saw and try to prove or disprove them.”

When I arrived at Horner’s camp I expected to find the busy director of a fully sponsored dig barking out orders to his staff. I was surprised to come upon a patient historical scientist, sitting crosslegged before a cervical vertebra from a 140-million-year-old
Apatosaurus
(formerly known as
Brontosaurus
), wondering what to make of it. Soon a reporter from a local paper arrived inquiring of Horner what this discovery meant for the history of dinosaurs. Did it change any of his theories? Where was the head? Was there more than one body at this site? Horner’s answers were those of a cautious scientist: “I don’t know yet.” “Beats me.” “We need more evidence.” “We’ll have to wait and see.” It was historical science at its best.

After two long days of exposing nothing but solid rock and my own ineptness at seeing bone within stone, one of the paleontologists pointed out that the rock I was about to toss away was a piece of bone that appeared to be part of a rib. If it was a rib, then the bone should retain its riblike shape as more of the overburden was chipped away. This it did for about a foot, until it suddenly flared to the right. Was it a rib, or something else? Horner moved in to check. “It could be part of the pelvis,” he suggested. If it was part of the pelvis, then it should also flare out to the left when more was uncovered. Sure enough, Horner’s prediction was verified by further digging.

In science, this process is called the
hypothetico-deductive method
, in which one forms a hypothesis based on existing data, deduces a prediction from the hypothesis, then tests the prediction against further data. For example, in 1981 Horner discovered a site in Montana that contained approximately thirty million fossil fragments of approximately ten thousand
Maiasaur
s in a bed measuring 1.25 miles by .25 miles. His hypothesizing began with a question: “What could such a deposit represent?”
²⁸
There was no evidence that predators had chewed the bones, yet many were broken in half lengthwise. Further, the bones were all arranged from east to west—the long dimension of the bone deposit. Small bones had been separated from bigger bones, and there were no bones of baby
Maiasaurs
, only those of individuals between nine and twenty-three feet long. What would cause the bones to splinter lengthwise? Why would the small bones be separated from the big bones? Was this one giant herd, all killed at the same time, or was it a dying ground over many years?

An early hypothesis—that a mud flow buried the herd alive—was rejected because “it didn’t make sense that even the most powerful flow of mud could break bones lengthwise. . . nor did it make sense that a herd of living animals buried in mud would end up with all their skeletons disarticulated.” Horner constructed another hypothesis. “It seemed that there had to be a twofold event,” he reasoned, “the dinosaurs dying in one incident and the bones being swept away in another.” Since there was a layer of volcanic ash 1.5 feet above the bone bed, volcanic activity was implicated in the death of the herd. Horner then deduced that only fossil bones would split lengthwise, and therefore the damage to the bones had occurred long after the dying event. His hypothesis and deduction led to his conclusion that the herd was “killed by the gases, smoke and ash of a volcanic
eruption. And if a huge eruption killed them all at once, then it might have also killed everything else around.” Then perhaps there was a flood, maybe from a breached lake, carrying the rotting bodies downstream, separating the big bones from the small, lighter bones, and giving the bones a uniform orientation.
²⁹

A paleontological dig is a good example of how hypotheticodeductive reasoning and historical sciences can make predictions based on initial data that are then verified or rejected by later historical evidence. Evolutionary theory is rooted in a rich array of data from the past that, while nonreplicable in a laboratory, are nevertheless valid sources of information that can be used to piece together specific events and test general hypotheses. While the specifics of evolution—how quickly it happens, what triggers species change, at which level of the organism it occurs—are still being studied and unraveled, the general theory of evolution is the most tested in science over the past century and a half. Scientists agree: Evolution happened.

The real attack of evolution, it will be seen, is not upon orthodox Christianity or even upon Christianity, but upon religion—the most basic fact in man’s existence and the most practical thing in life. If taken seriously and made the basis of a philosophy of life, it would eliminate love and carry man back to a struggle of tooth and claw.

—William Jennings Bryan, closing statement, Scopes trial, 1925

On a thickly muggy and stiflingly hot summer day in 1925, William Jennings Bryan arose to speak at the end of the trial of the century. He had carefully crafted his speech to express the deeper question he felt had been put on trial in Dayton, Tennessee: not, as most observers believed, whether a high school science teacher had lectured his students on Darwin’s theory of evolution, but rather who would win the battle for humanity’s soul. “The soul is immortal and religion deals with the soul,” he wrote in a statement epigrammatically poignant; “the logical effect of the evolutionary hypothesis is to undermine religion and thus affect the soul.”

Bryan was never actually allowed to deliver his dramatic final speech in the Scopes “Monkey Trial.” The judge determined that it was irrelevant to the case—the same ruling he made against the defense when they called evolutionary biologists as expert witnesses—
and Bryan died rather unceremoniously two days after the trial’s end. But the speech was subsequently published as a booklet heroically entitled
Bryan’s Last Speech: The Most Powerful Argument against Evolution Ever Made
.
¹
The speech is an insight into why so many people resist the theory of evolution: the belief, and fear, that accepting evolution leads to the breakdown of morality and the loss of meaning for humanity. The syllogistic reasoning goes as follows:

Evolution implies that there is no God, therefore
. . .

Belief in the theory of evolution leads to atheism, therefore
. . .

Without a belief in God there can be no morality or meaning, therefore
. . .

Without morality and meaning there is no basis for a civil society, therefore
. . .

Without a civil society we will be reduced to living like brute animals
.

This
is what bothers people about evolutionary theory, not the technical details of the science. Most folks don’t give one whit about adaptive radiation, allopatric speciation, phenotypic variation, assortative mating, allometry and heterochrony, adaptation and exaptation, gradualism and punctuated equilibrium, and the like. What they do care about is whether teaching evolution will make their kids reject God, allow criminals and sinners to blame their genes for their actions, and generally cause society to fall apart.

Where did they get such an idea?

Forget the Lindbergh kidnapping trial, the Manson murder trial, even the O.J. media trial. The Scopes trial really did beat them all as a test of our humanity. It was bigger than life, from the issues at hand to the characters involved.
²

It helps to know that the trial was initially instigated as a publicity stunt, dreamed up by the fledgling American Civil Liberties Union in collaboration with the city leaders of the economically struggling Tennessee town of Dayton. On one side of the dock was the most famous defense attorney of his era, Clarence Darrow; on the other was the century’s preeminent orator and defender of the faith, three-time presidential candidate Bryan. Covering the trial for the
Baltimore Sun
was the unapologetically cynical reporter H. L. Mencken, who meted out such barbs as this: “If the Anti-Evolutionists in Tennessee were aware of the existence of any other religions than their own, they might realize that it is the very genius of religion itself to evolve from primary forms to higher forms. The author of the anti-evolution bill is obviously nearer in mental development to the nomads of early biblical times than he is to the intelligence of the young man who is under trial.”
³

That young man, John Thomas Scopes, was a substitute teacher from a neighboring county who, by his own admission, volunteered to challenge Tennessee’s “anti-evolution” law because, in addition to being a freethinker, he thought that the extended stay in Dayton over the summer and the ensuing attention might help his cause in a local love interest. The ACLU was sure they would lose in Dayton—giving them a chance to appeal to the Tennessee State Supreme Court and eventually land the case in the U.S. Supreme
Court. From the start, court cases about teaching evolution have been about everything
but
the science.

Most people think that science scored a knockout victory in Tennessee. Reading Mencken would certainly lead to this conclusion. Of Bryan he gibed: “Once he had one leg in the White House and the nation trembled under his roars. Now he is a tinpot pope in the Coca-Cola belt and a brother to the forlorn pastors who belabor half-wits in galvanized iron tabernacles behind the railroad yards. . . . It is a tragedy, indeed, to begin life as a hero and to end it as a buffoon.” In fact, this was no victory for evolution or science, and it may surprise readers to learn that Scopes’s guilty verdict was overturned not on the merits of the case but on a minor technicality involving the levying of a fine of over $50 by a judge instead of a jury. Embarrassed by the bad publicity the state of Tennessee was receiving, the state legislators used a technical misstep to prevent the case from reaching the state’s supreme court. Who can blame them after reading comments like this from Mencken: “It serves notice on the country that Neanderthal man is organizing in these forlorn backwaters of the land, led by a fanatic, rid of sense and devoid of conscience.” Worse, the controversy stirred by the trial made textbook publishers and state boards of education reluctant to deal with evolution in any manner. A study of high school biology textbooks before and after the trial revealed that the subject of evolution simply disappeared from the curriculum and was not taught for decades.
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