It has come to my attention recently that I might have readers who are unfamiliar with evolution, so I’ve decided to start a series of posts on the topic. And at the risk of being too basic, I’m going to start with the basics. (This is a slightly modified re-posting of something I said on a message board some time ago. The other posts in the series will be original.)
“Evolution”, in this sense, refers to the fact that species change over time. The “theory of evolution” refers to the accepted explanation of this fact, which has itself evolved over time starting from Charles Darwin’s original version. The theory is that some traits make individuals more likely to survive than others (this is called natural selection) or more likely to reproduce (sexual selection), and that these traits become more common while traits having the opposite effect become less common.