I mentioned in an earlier post (A Science Question for Michele Bachmann) that science is often the first casualty of presidential politics. Here is an example. When Governor and Republican presidential candidate Rick Perry was recently asked about his views on evolution he responded by saying “It’s a theory that’s out there.” Science-denying candidates like Mr. Perry will often speak the word theory with special disdain as though it was some sort of pejorative.
Theories are how science works. A scientist starts by making observations and measurements of physical phenomena. The next step is to try to identify a trend in the observations. Then the trend is used to try to predict future events. If the predictions are successful, then the scientist will present this trend as her theory as to how the physical phenomena are governed. This is the scientific method.
The inference that Mr. Perry is hoping you will draw from his verbal histrionics is that being a “theory” is a bad thing. But here’s the rub. Theories, while they can be refined and improved upon over time, always remain theories. It’s not as though theories are relegated to some sort of purgatory awaiting promotion to scientific nirvana. Theories stay theories. This does not make them wrong, untrustworthy or deserving of scorn. Consider gravity, or to use its longer name, the Universal Theory of Gravitation. It is has been used for hundreds of years to explain why apples fall to the earth, how the planets orbit the sun and to determine the design of rockets. Yet it is still a theory, an equation which helps to explain and predict the movement of objects with remarkable accuracy.
In the future I may post a blog on the Theory of Evolution and the voyage of Charles Darwin’s boat, the Beagle, but for today let’s use the incredibly short Common Science summary of evolution. When cells replicate, they usually create exact copies of their DNA in the new cell. Sometimes a mistake, or mutation, occurs and the new cell has different DNA from the original cell. If the mutation is not viable, the cell dies. If the cells with the mutated DNA are viable they live on and start reproducing new cells which also have this mutation. Mutations are the key to evolution.
Now let’s move from a single cell to multicellular organisms. The definition of a species is a group of organisms which can reproduce by sharing DNA though sexual reproduction or pollination. To understand how evolution works, consider dividing a species into two distinct geographic areas such that no DNA is shared between the two groups. As the two groups live separately, different accumulated mutations are passed on in the gene pools of the two groups. With the passage of enough time, millions and millions of years, the accumulated mutations will be great enough that the two groups can no longer exchange DNA to create off-spring. Now instead of one species there are two. This is evolution.
When Mr. Perry makes a statement denigrating the Theory of Evolution it is with calculated intent. His pollsters will tell him, with depressing accuracy, that 60-70% of self-identified Republican primary voters, when asked if they believe in the Theory of Evolution will say “no.” The challenge for a scientifically inclined person like me is trying to understand what they mean when they say “no”. What part of the explanation above do they not accept? Do they not believe that DNA mutates? Do they not believe that after enough cumulative mutations that isolated groups can no longer reproduce?
Thinking through the questions above can drive me to utter despair. I just don’t get it. Don’t people understand that the Theory of Evolution, in addition to explaining how life developed on earth, provides the underpinnings for much of the modern world, medicine, agriculture, dog shows …. I invite any of my readers to help me understand what they mean when they say “no.”
Perhaps we can run an experiment with Mr. Perry. We can suspend a large apple on a string above him on a campaign podium. Then we can explain to him that there is a conspiracy of some elite scientists who are promoting a theory that some unseen, inexplicable force exists that causes all objects in the universe to attract one another. They we can smile and tell him that we are going to go ahead a cut the string because, after all, gravity is just a “theory” that’s out there.
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