What is evolution?

Evolution describes how living things change across generations as genetic variations are passed on. Charles Darwin and Alfred Russel Wallace independently proposed natural selection in the mid-19th century: individuals with traits better suited to their environment tend to survive and reproduce, so those traits become more common over time. Combined with genetics — unknown to Darwin — this explains how new species arise from common ancestors. The evidence spans fossils, DNA, and directly observed changes, such as bacteria evolving antibiotic resistance. All life on Earth shares a common ancestor that lived billions of years ago.