How Evolution Works

PBS Eons uses all three of its hosts and the Smithsonian National Museum of Natural History's Deep Time Hall to explain how evolution actually works, and how scientists came to understand it. At about 12 minutes, it is one of the clearest short introductions to the subject.

What the video covers

• Why evolution was such a revolutionary idea when it was first proposed
• How evolution works, step by step
• How fossils and the history of life on display in the Deep Time Hall support it

The science

Evolution is change in the inherited traits of populations over generations. Charles Darwin and Alfred Russel Wallace proposed natural selection in 1858: individuals with traits better suited to their environment tend to survive and reproduce more, so those traits become more common. Mutation, genetic drift and gene flow also shape populations. Since then, evidence from fossils, anatomy, genetics and direct observation (from antibiotic-resistant bacteria to changes in finch beaks) has made evolution one of the best-supported theories in science. In science, a "theory" is a well-tested explanation, not a guess.

Related reading: Evidence Supporting Evolution, Natural Selection and Its Role in Evolution and Creationism.