According to this theory, all species are descended from a common ancestor and that over time, these species have changed and adapted to their environments in order to survive. This process of change is driven by natural selection, which is the process by which organisms that are better adapted to their environment are more likely to survive and reproduce. Over time, this can lead to significant changes in a population, and even to the emergence of new species.

The idea of evolution was first proposed by Charles Darwin and Alfred Russel Wallace in the mid-19th century, and it has since become one of the most important and well-supported theories in science. Evidence for evolution comes from a wide variety of sources, including the fossil record, comparative anatomy, molecular biology, and genetics.