Evolution is simply the change over time in the frequencies of different heritable traits (that is, the frequencies of different genes) in a group of organisms. One year, half the birds have blue eyes and the other half have brown. Some years later, two thirds of the birds have blue eyes. If eye color is a heritable trait, that is, one that is passed from parent to offspring, then that change is evolution.
Darwin's big idea was coming up with a process that could cause these changes. This theory of natural selection is simply a process in which heritable traits that help an organism survive in its current environment occur more frequently in subsequent generations. In other words, genes (the heritable traits) that are favored (help survival) increase over time. Evolution by natural selection really is that simple, regardless of what you may have heard to the contrary.
Darwin, the father of evolutionary theory (refer to Chapter 1), did a phenomenally good job of piecing this part of evolutionary process together, but he could only hypothesize about the underlying details of what he called descent with modification. What he didn't understand was the underlying genetic mechanism that was responsible.
Was this article helpful?