We are sometimes asked by a creationist for the one best piece of evidence which “proves” Darwin’s theory of evolution. By asking that question, the creationist seeks to avoid what he regards as the distasteful task of studying evolution. He’s looking for a shortcut so he can focus on only one item and perhaps refute it, hoping that this will suffice to demolish the theory. But the creationist’s question reveals not only his ignorance of evolution, but a fundamental misunderstanding of science itself.
In science, theories are never proven to be true. Proof is something that happens in geometry, not science. The only proof of which science is capable is proof that a theory is false. That will happen when something is verifiably observed that undeniably contradicts an essential feature of the theory.
The best-known recent example comes from cosmology. The discovery of the cosmic microwave background radiation was predicted by the Big Bang theory, and its existence was inconsistent with the Steady State theory, which was thereby discredited. Big Bang wasn’t proven true — although one of its predictions was spectacularly confirmed — but Steady State was conclusively proven false. This illustrates a vital characteristic of scientific theories — they’re testable.
Note: Like so many other superseded scientific theories that litter the dustbin of science, Steady State may be mentioned as part of the history of science, but it’s not taught in school as a still-viable alternative to the Big Bang. It would be incredibly irresponsible to do so in the interest of “academic freedom,” allowing the children to decide which theory they prefer.
Instead of being proven true, a scientific theory can aspire only to being solidly supported by tests and observations. In science it’s the accumulation of supporting evidence that raises an untested hypothesis to the ultimate status of being a well-tested and therefore widely accepted theory. But all scientific theories are, in principle, subject to the same fate that was suffered by the Steady State theory.
To the disappointment of the creationist questioner, there is no one piece of evidence that “proves” the theory of evolution. The theory’s acceptance rests on the totality of all the evidence. Any one item, considered alone, may have many possible explanations, and to a casual observer, a non-evolutionary explanation may seem as plausible as any other. (Perhaps the questioned fossil is a fake, or a jumbled collection of several fossils, or perhaps it was accidentally dropped in the wrong place by a clumsy backpacker.) But what of all the other evidence?
The “clumsy backpacker” explanation, even if true for one item, can’t account for everything else that supports evolution. Can an alternate explanation survive the same rigorous testing that the existing theory has survived? Is it consistent with other branches of science? The theory of evolution passes those tests. No alternative explanation comes close.
That’s the problem facing evolution deniers when they attack evolution by focusing on one piece of evidence and trying to explain it away. Even if there were a bad data point (and there have been some), all the rest still stands, and the quantity is enormous. The more evidence an existing theory explains, the more difficult it becomes to find excuses for it; and it’s still more difficult to devise a credible alternative explanation for all of that evidence.
The reason there is nearly universal acceptance among scientists for the theory of evolution is that all the evidence thus far examined supports the theory — and none contradicts it. It’s not just the biological evidence from the fossil record, comparative anatomy, and DNA analysis. It’s also that the theory is consistent with other fields of science, such as geology, plate tectonics, astronomy, and physics.
Note: In all scientific fields, there are issues not yet resolved, and there probably always will be. Such items are research candidates, not contradictions or weaknesses of existing theory.
Darwin’s biggest problem, largely unnoticed by today’s creationists, didn’t come from experts in his own field, but from non-biological sciences. Darwin understood that the grand course of evolution requires hundreds of millions of years, but Lord Kelvin’s calculations of the age of the earth and the sun — before anyone knew about nuclear physics — indicated that the earth and the sun were far younger than the eons Darwin required. Later discoveries showed that Kelvin, through no fault of his own, was exceedingly wrong, and that removed the greatest obstacle to acceptance of evolution. The concurrence of several independent lines of evidence is highly unlikely unless a theory is indeed an accurate explanation of the phenomena it addresses.
It’s important to note that a theory which is supported by all the available evidence, like evolution, is not the same as a “theory” like intelligent design, which will be consistent with any evidence that might turn up. A “theory” that will always be consistent with everything doesn’t really explain anything. It may be an excellent theological doctrine, but it isn’t a scientific theory at all, because no test or observation could ever disprove it.
Although there’s no one smoking gun that proves evolution, there can be a smoking gun that disproves it, as happened to the Steady State theory. A good example would have been Piltdown Man. Creationists constantly cite this famous hoax as a “typical” example of the fraud that sustains evolution. In their supreme ignorance, they imagine that it was universally hailed as “proof” of evolution in hundreds of papers in the scientific journals — until some plucky creationist (never named) dared to challenge the scientific orthodoxy and showed that it was a fake. All of this “history” is wrong.
What the creationists don’t understand is that virtually no competent evolutionary biologist knew what to make of Piltdown Man, because it contradicted the theory of evolution. It was scientists — not creationists — who demonstrated that it was bogus. Evolutionary biologists thought that evidence of man’s ancestors would probably be found in Africa, because that’s where so many non-human primates are found. There are no non-human primates native to England, so it’s quite impossible for man to have evolved there, or on any other island with no ancestral candidates. If Piltdown man were real, Darwin’s theory wouldn’t be able to explain it.
So our answer to the creationist in search of evolution’s smoking gun is that we don’t have one for you. Instead, we have a constantly-growing mountain of evidence, and that’s what you’ll have to deal with. But if you want a simple way to prove that Darwin was wrong, go out and find your own smoking gun — the one that will contradict evolution. Fame awaits you.
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