Why Darwin Matters (10 page)

Burden of Proof, or, extraordinary claims require extraordinary evidence
.

Darwin’s original claim of evolution by means of natural selection was an extraordinary claim in its time, so he was required to provide extraordinary evidence for it. He did, and evidence has continued accumulating ever since. Today, the burden of proof is on creationists and Intelligent Design advocates to provide extraordinary evidence for their extraordinary claim that a supernatural being of great power and intelligence performed a supernatural act in place of or contrary to natural law. They have yet to do so.

Either-Or Fallacy, or, disproving A does not prove B
.

The either-or fallacy is the false assumption that there are only two positions, A and B, so if A is wrong then B must be right. The fallacy is that discrediting A does not demonstrate B. Both A and B could be wrong and a third alternative could be correct. Creationists employ the either-or fallacy when they claim that life was either divinely created or naturally evolved. By attempting to discredit evolution they hope to draw the conclusion that creationism is true. In science, however, it is not enough to just debunk the accepted theory. You must also replace it with a theory that explains both the “normal” data accounted for by the old theory as well as some of the “anomalous” data not accounted for by the old theory. At the end of my debate with Kent Hovind, for example, he was asked by an audience member: “What is the best evidence for the creation?” He answered: “The impossibility of the contrary” (that is, evolution). In that simple statement, Hovind confessed the scientific sin of creationism and Intelligent Design: Disproving evolution does not prove creationism.

The Fossil Fallacy, or, one datum does not a science make
.

In debates with creationists they often demand “just one transitional fossil” that proves evolution, pointing to a gap in the fossil record. When I fill the gap—for example, with
Ambulocetus natans
, a transitional fossil between ancient land mammals and modern whales—they respond that there are now
two gaps
in the fossil record! This is a clever retort, but it reveals a deep error in epistemology that I call the
Fossil Fallacy:
the belief that a single “fossil”—one bit of data—constitutes proof of a multifarious process or historical sequence.
⁵

Proof is derived not through a single piece of evidence, but through that convergence of evidence from numerous lines of inquiry, all of which point to an unmistakable conclusion. We know evolution happened not because of a single transitional fossil such as
Ambulocetus natans
, but because of the convergence of evidence from such diverse fields as geology, paleontology, biogeography, comparative anatomy and physiology, molecular biology, genetics, and many more. Paleontologist Donald Prothero, for example, employs the convergence technique in revealing that in addition to at least eight transitional fossils from land mammals to whales, DNA from living specimens reveals that modern whales descended from even-toed hoofed mammals called
artiodactyls
. Whales, it turns out, are most closely related to the hippopotamus.
⁶

No single discovery from any one field constitutes proof of evolution. It is the mass of data together, converging to reveal that life evolved in a specific sequence by a particular process, that makes the theory of evolution a singular landmark in our understanding of the world.

Methodological Naturalism, or, no miracles allowed
.

In one of Sidney Harris’s most poignant cartoons, two scientists are at a blackboard filled with equations, in which the words “
THEN A MIRACLE OCCURS
” appear in the middle. The caption has one scientist saying to the other: “I
THINK YOU NEED TO BE MORE EXPLICIT HERE IN STEP TWO
.” This is what we call the
God of the Gaps
argument—wherever an apparent gap exists in scientific knowledge, this is where God interjects a miracle. Intelligent Design advocates argue something like this:

• X looks designed

• I can’t think of how X could have been designed naturally

• Therefore X must have been designed supernaturally

This is comparable to the “plane problem” of Isaac Newton’s time: The planets all lie in a plane (the plane of the ecliptic) and revolve about the sun in the same direction. Newton found this arrangement to be so improbable that he invoked God as an explanation at the end of his magisterial work
Principia Mathematica:
“This most beautiful system of the sun, planets, and comets could only proceed from the counsel and dominion of an intelligent and powerful Being.”
⁷
Why don’t creationists use this argument any more? Because astronomers have filled that gap with a natural explanation.

The technical term for this process is
methodological naturalism
, and Intelligent Design theorists harp about it incessantly. Methodological naturalism holds that life is the result of natural processes in a system of material causes and effects that does not allow, or need, the introduction of supernatural forces. In his book
Darwin on Trial
, University of California, Berkeley, law professor Phillip Johnson, the founding father of the Intelligent Design
movement, accused scientists of unfairly defining God out of the picture by limiting the search to only natural causes, and argued that scientists who postulate that there are supernatural forces or interventions at work in the natural world are being pushed out of the scientific arena on the basis of nothing more than a fundamental rule of the game. Johnson wants the rules of the game changed to allow
methodological supernaturalism
.

Okay, let’s change the rules. Let’s allow methodological supernaturalism into science. What would that look like? How would that work? What would we do with supernaturalism? For the sake of argument, let’s assume that Intelligent Design theorists have suddenly become curious about how exactly the Intelligent Designer operates. As researchers who are now given entrée into the scientific stadium with an addendum to the rules that allows supernaturalism, they call a time out during the game to announce, “
THEN A MIRACLE OCCURS
.” What do we do now? Do we halt all future experiments? Since science is what scientists do, what are we supposed to
do
with such supernatural explanations? My response to the God of the Gaps argument is: “I
THINK YOU NEED TO BE MORE EXPLICIT HERE IN STEP TWO
.”

Even if Intelligent Design advocates are willing to continue searching, what will they do if they discover a new force of nature that accounts for design? How will they identify it? Will it be considered a natural force, or a supernatural force? When electromagnetism and the weak and strong nuclear forces were discovered in the nineteenth and twentieth centuries, scientists did not identify them as supernatural forces; they simply added them to the known forces of nature. If IDers eschew all attempts to provide a naturalistic explanation for life, they abandon science altogether.
⁸

There is no such thing as the supernatural or the paranormal. There is only the natural, the normal, and mysteries we have yet to explain
.

As we have seen, creationists and Intelligent Design theorists have made dozens of arguments trying to disprove evolution, most hinging on the truly meaningless search for a single piece of data that will fill the gap of the week. But much of their recent success in classrooms and with school boards has been in using the language of science to argue that the data support Intelligent Design rather than evolution. Here I present their ten most cogent—and most commonly presented—arguments, followed by an evolutionary response grounded in the latest scientific theories on the origin and evolution of the universe and life.
⁹

The Anthropic Principle:

The universe is fine tuned for life
.

We begin with what I consider to be the best scientific argument that creationists and Intelligent Design theorists have in their arsenal: The universe is finely tuned and delicately balanced to support life. Change any number of physical parameters or initial conditions of the universe by even the tiniest amount, and life would not be possible. Fine tuning implies that there is a fine tuner, an Intelligent Designer, a God.

There is no shortage of observations from leading scientists on this condition of the cosmos. No less a personage than Stephen Hawking wrote:

Why is the universe so close to the dividing line between collapsing again and expanding indefinitely? In order to be as close as we are now, the rate of expansion early on had to be chosen fantastically accurately. If the rate of expansion one second after the big bang had been less by one part in 10
¹⁰
, the universe would have
collapsed after a few million years. If it had been greater by one part in 10
¹⁰
, the universe would have been essentially empty after a few million years. In neither case would it have lasted long enough for life to develop. Thus one either has to appeal to the anthropic principle or find some physical explanation of why the universe is the way it is.
¹⁰

What is this supernaturally appealing “anthropic principle”? In
The Anthropic Cosmological Principle
, the physicists John Barrow and Frank Tipler define the term: “It is not only man that is adapted to the universe. The universe is adapted to man. Imagine a universe in which one or another of the fundamental dimensionless constants of physics is altered by a few percent one way or the other. Man could never come into being in such a universe. That is the central point of the anthropic principle. According to the principle, a life-giving factor lies at the center of the whole machinery and design of the world.”
¹¹
Of course, thinking of man as the center of the universe has not had a strong track record in science, but let’s set aside Copernican reservations in favor of contemporary astronomy.

Sir Martin Rees, Britain’s Astronomer Royal, argues that “our emergence from a simple Big Bang was sensitive to six ‘cosmic numbers.’ Had these numbers not been ‘well tuned,’ the gradual unfolding of layer upon layer of complexity would have been quenched.”
¹²
The six cosmic numbers are:

Ω (omega) = 1, the amount of matter in the universe, such that if Ω was greater than one, it would have collapsed long ago, and if Ω was less than one, no galaxies would have formed.

ε (epsilon) = .007, how firmly atomic nuclei bind together, such that if epsilon were .006 or .008, matter could not exist as it does.

D = 3, the number of dimensions in which we live, such that if D were 2 or 4, life could not exist.

N = 10
³⁶
, the ratio of the strength of gravity to that of electromagnetism, such that if it had just a few less zeros, the universe would be too young and too small for life to evolve.

Q = 1/100,000, the fabric of the universe, such that if Q were smaller, the universe would be featureless, and if Q were larger, the universe would be dominated by giant black holes.

λ (lambda) = 0.7, the cosmological constant, or “antigravity” force, that is causing the universe to expand at an accelerating rate, such that if λ were larger, it would have prevented stars and galaxies from forming.

Change these relationships and stars, planets, and life could not exist. Thus, this is not just the best of all possible worlds, it is the
only
possible world—and a world crafted with remarkable math skills, to boot. Intelligent Design theorists consider these numbers to be
complex
and
specified
, and thus the fine-tuned anthropic principle is evidence of design.
¹³

First, the universe is not so finely tuned for life. The vast majority of the universe is empty space, and the vast majority of what little matter there is, is completely inhospitable to life, including most planets. In its 13.7-billion-year history, the anthropic conditions for life were nonexistent for several billion years—it is only during a narrow slice of recent time that the universe became finely tuned for life, and only a minuscule portion of the universe is hospitable. John Barrow and his colleague John Webb also note that the so-called “constants” of nature—the speed of light, gravitation, the
mass of the electron—may be inconstant, varying over time from the Big Bang to the present, making the universe finely tuned only
now
.
¹⁴

Second, our universe is not finely tuned for us (the strong anthropic principle), we are finely tuned for it (the weak anthropic principle). It is entirely possible that a completely different form of life could be based on another type of physics. We are carbon chauvinists, Carl Sagan liked to point out; life based on some other element (such as silicon) is entirely possible, but because we know of only one type, it is difficult for us to think outside the chemical box.

Third, our universe may not be that exceptional. String theory, for example, allows for 10
⁵⁰⁰
possible worlds, all with different selfconsistent laws and constants.
¹⁵
That’s a 1-followed-by-500-zeros possible universes (recall that twelve zeros is a trillion!). If that is true, it would be miraculous if there were not intelligent life in a number of them. The physicist and astronomer Victor Stenger created a computer model that analyzes what just a hundred different universes would be like under constants different from our own, ranging from five orders of magnitude above to five orders of magnitude below their values in our universe. He discovered that longlived stars of at least one billion years—necessary for the production of life-giving heavy elements—would emerge within a wide range of parameters in at least half of the universes in his model.
¹⁶