Scientific definitions of Evolution
“Evolution is a process that results in heritable changes in a population spread over many generations.”
"Evolution can be precisely defined as any change in the frequency of alleles within a gene pool from one generation to the next."
Standard dictionaries definitions
"evolution: The gradual process by which the present diversity of plant and animal life arose from the earliest and most primitive organisms, which is believed to have been continuing for the past 3000 million years." Oxford Concise Science Dictionary
"evolution: ...the doctrine according to which higher forms of life have gradually arisen out of lower.." - Chambers
"evolution: ...the development of a species, organism, or organ from its original or primitive state to its present or specialized state; phylogeny or ontogeny" - Webster's
Science never provides us with the definitive, final answer to any question. This means that one doesn't "believe" in evolution any more than one "believes" in organic chemistry. Rather, one accepts evolution as an explanation well supported by fact, as a theory that explains facts and makes sense of them, and as a productive and useful way to conduct further research. This doesn't mean that anyone ever has to accept evolution to learn biology; but it does mean that no person is fully educated without an understanding of it.
Science never provides absolute knowledge. It answers limited questions about nature in a limited (but very useful way). This means that science by itself can never address questions of meaning and purpose, even though such questions are important to each of us.
Kenneth R. Miller
Professor of Biology