A century and a half ago, Charles Darwin offered the world a single, simple scientific explanation for the diversity of life on Earth: evolution by natural selection. Since then, countless scientists—whether fighting viruses, decoding DNA or analyzing the fossil record—have found that Darwin's work is fundamental to their own.

Modern scientists can now answer questions about the natural world in ways Darwin never could. New tools and technologies, such as DNA analyses, can reveal unexpected relationships between seemingly dissimilar groups. Accurate fossil dating methods show that evolution proceeds at variable rates and is not always gradual. And sophisticated studies of wild populations provide insights into how new species are formed. Darwin would be amazed—and delighted—to see how our new knowledge has helped advance his theory.