It happened again. A reader sent me an e-mail message in which she complained that evolution "is being taught to my grandchildren as fact, and not as the theory it is."
That word "theory" has caused a lot of misunderstanding. It makes many people believe that evolution is merely an idea, a guess or an unproven hypothesis.
Nothing could be farther from the truth. Scientists use the word "theory" in a very different way. To a scientist, the word "theory" means a model, a sort of map that takes in a lot of separate observations and ties them together into an understandable whole. A good theory also points the way to new observations and new understanding.
Here's the way it works:
Scientists make observations of nature. For example, since ancient times scientists had been observing the different kinds of animals and plants that live in our world: trees, grasses, flowers, pond scum, insects, fish, amphibians, reptiles, mammals and more.
How did these different kinds of creatures come into being? The Bible said they were created by God over a period of six days.
But then geologists began to find evidence that the Earth was much, much older than the Bible claimed. Paleontologists found fossils of creatures that have long been extinct. And microscopes showed a teeming world of bacteria and single-celled creatures.
How to make sense out of this bewildering profusion of life?
Charles Darwin made many, many observations of living creatures, both while he served as a naturalist on the HMS Beagle's globe-spanning voyage and for years afterward, at home in England. He came up with an idea which he believed could help explain how the different kinds of organisms on Earth came into being.
His basic idea of evolution through natural selection is actually quite simple. Darwin noted that all creatures struggle to survive. Those that survive best are those which are best fitted for the environment in which they live. And those that survive best produce the most offspring.
Environments change over time, however. A species that was beautifully adapted to survive in one environment may be snuffed out when that environment changes.
Now, not all of a creatures' offspring are identical to their parents — or to each other. Each offspring displays some difference in its makeup. The differences are usually so slight that they have no effect on the offspring's chances of survival. Some differences are harmful, and those individuals die off.
But some differences allow the offspring to survive better in the new environment in which it exists. Those offspring live longer and have more offspring of their own.
Thus, over time, species change. They evolve. Those that are better adapted to their environment thrive. Those that are not perish.
That is Darwin's concept of evolution through natural selection. It's simple. And it doesn't need special guidance by some superhuman entity.
Darwin's idea made sense out of all the myriad observations of nature that had been made before him. It all fit into an understandable pattern. Not only that, Darwin's theory pointed the way to new observations, new understandings.
Scientists don't accept theories because they're elegant or popular. They test ideas with measurements and observations, with experiments that are as rigorous as they can create. Darwin's concept has been tested thoroughly.
For more than a century and a half people have tested Darwin's theory. Nothing has been found that refutes it. From bacteria to basketball players, evolution through natural selection explains nature's workings.
Many people oppose Darwin because the theory of evolution displaced God as creator of life. Many are especially unhappy with the idea that we humans are merely another species that has come about through evolution by natural selection, not by a special creation of God.
The scientists' constant testing of ideas is something that St. Paul recommended to the Thessalonians: Prove all things; hold fast that which is good. (1 Thessalonians 5:21)
Darwin's theory of evolution has passed every test. It explains how nature works. It makes sense of biology and genetics. It is not a guess or hypothesis. It is as factual as anything we know.
Bova, a Naples resident, is the author of more than 120 books, including "The Return," his latest futuristic novel. Bova's Web site address is www.benbova.com.
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