I thought I’d take a slightly different approach to my next post on evolution. I’ve written three posts designed to help the non-scientist who doesn’t believe in evolution get a handle on the basics and begin an understanding that will ultimately lead to bringing the non-believer over to the side of truth, enlightenment and the beauty of life’s diversity. Yes, evolution is true. It’s a scientific fact. In this post, I will tackle one of the more common things people bring up as a reason they doubt evolution.

• It’s just a theory, right?

This is a fair question from the non-scientist (a group to which I belong) because of the common use of the word theory. When used by non-scientists a theory is a guess, a conjecture, a speculative reason for something. “My theory is that men and women can’t be friends,” is an example of a common usage of the word ‘theory’. “I have a theory that chewing gum leads to tooth decay,” would be another example. These are my guesses, based on nothing other than my opinion, which I derived from observation and a good dose of common sense. Are they true? I have no idea, they’re “just theories.”

In scientific terms, my two theories are really just hypotheses. I’ve observed men and women who started out as friends later become lovers. I therefore conclude this would happen every time. I’ve heard of cavities and I know there’s sugar in some gums and so I brilliantly deduce that all that gum chewing must cause sugar to eat away at our tooth enamel and cause cavities. Many non-scientists will stop there and carry around these hypotheses in their mental Rolodex as if they were probably facts. The reality is that until I start testing my “theories” they remain speculative conjecture, or guesses. So the non-scientists among us confuse our type of theories with the scientific theories.

Scientists make propositions, or a set of propositions, to explain the occurrence of some specified group of phenomena that they have witnessed. This is their hypothesis for why these things occur and they will now set about testing it. Scientific testing is rigorous, deliberate and slow. The scientist will challenge his or her own ideas, trying to find errors which then lead to a discarding of the original hypothesis. Other scientists will challenge the findings of their peers and seek to confirm or disprove them. Science has a built-in mechanism of correction. This method of truth-seeking can be plodding, but it is painstakingly persistent in its search for answers, even if the answers turn out to be unsettling.

The result of all this testing of hypotheses is a collection of observable phenomena that can be expressed as quantifiable rules or laws, supported by data and put forth as an explanation for the phenomena: a Theory.

Charles Darwin, in 1859, obliterated the common belief of the time in a creationist origin for the variety of life on Earth. In one small book, he laid out the beauty and majesty of natural selection; of the adaptation of living organisms to their environment and the reproductive success of the variations best suited to their environment. Evolution, which simply means that living species undergo change over time, is the scientific theory that allows all the rest of biology to make sense. It has been tested by thousands of scientists for over 150 years and never found wanting.

Let’s look at what it takes for a hypothesis to become a Scientific Theory:

• Consistency
• Descriptive of observable phenomena
• Testable and falsifiable
• Based on controlled, repeated experiments
• Correctable as new data is discovered
• Tentative, ie not asserting it as certainty

It is probably this last component that causes the non-scientist to declare “Aha! It’s not an absolute, infallible and undisputed fact! I refuse to believe it.” What we need to understand is that this is just how scientists are. They are always open to new data or evidence that will prove them wrong! Scientists are skeptical, as we all should be. But the Theory of Evolution has not been proven wrong. In fact, the evidence supporting it is so overwhelming that it is as close to an absolute, infallible and undisputed fact as science can get. Here’s how simple it would be to show evolution was false:

• Find fossils of rabbits mixed in with dinosaur fossils.

It has never happened. In fact, the fossil record shows the clear and relentless evolution of life as species of plants and animals change over time as evolution predicts. New species appear and then disappear, again, just as evolution predicts.

So as I help the non-scientist advance relentlessly onward from non-belief in evolution to the Aha moment where the truth shines through, we may now remove this link in the chain. Evolution is a Theory, but there is no “just” about it. It is just as factual as the Theory of Gravity, the Germ Theory of Disease, the Theory of Relativity and Plate Tectonic Theory.