Friday, April 13, 2012

Evolution is Fact And Theory

Just as Copernicus' heliocentric theory of the solar system was controversial in his day, the theory of evolution harbours lingering controversy today. Accepted as fact by scientists worldwide, its opponents argue that evolution is "just a theory." So which is it?

The answer is both.

The word "theory" in everyday English is used interchangeably with the word "hypothesis." To do so in scienctific context is impermissible, as the word "theory" has a very specific, unwavering meaning in the science world.

Theory: In science, a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.
Hypothesis: A tentative statement about the natural world leading to deductions that can be tested.

(Definitions from the National Academy of Sciences, 1998)

The glaring difference between these terms, is that a hypothesis is untested. It is a conjecture—mere speculation. This speculation may be based on sound, deductive reasoning supported by a heavy body of research, but it is still speculation, and has yet to be verified. A theory, on the other hand, has been tested and verified, and accepted as truth.

NB: Nothing can ever be proved in science (with the exception of mathematics), only failed to be disproved.

It is a fact that all life on earth is related. It is a fact that individuals of the same species exhibit differential survival. It is a fact that only some genes in a population are propagated to the next generation. And it is a fact that there are quantifiable causes of the differential survival of genes. Evolution is the theory that explains these facts. Simple as that.

If in the future you are unfortunate enough to encounter a history-denier who tries to say that evolution is "just a theory," consider yourself properly armed against their "argument." Keep in mind, also, that evolution has nothing to say about the origin of life, only the process by which life changes over time.


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