The theory of evolution explains how living things change over time through a process called natural selection. This means that organisms with traits that help them survive in their environment are more likely to reproduce and pass those traits to their offspring. Over many generations, these small changes can lead to the development of new species. One famous figure associated with this theory is Charles Darwin, who proposed that all species share a common ancestor. His observations of different species, such as the finches on the Galápagos Islands, helped him understand how adaptation works. This theory has become a fundamental concept in biology.