Why Is Evolution Important? The discovery and understanding of the processes of evolution represent one of the most powerful achievements in the history of science. Evolution successfully explains the diversity of life on Earth and has been confirmed repeatedly through observation and experiment in a broad spectrum of scientific disciplines. Evolutionary science provides the foundation for modern biology. It has opened the door to entirely new types of medical, agricultural, and environmental research, and has led to the devel- opment of technologies that can help prevent and combat disease. Regrettably, effective science education in our schools is being undermined by efforts to introduce non-scientific concepts about evolution into science classrooms. How Science Works The study of evolution provides an excellent example of how scientists go about their work. They observe nature and ask testable questions about the natural world, test those questions through experiment and new observations, and construct explanations of evolution based on evidence. As scientists gather new results and findings, they continue to refine their ideas. Explanations are altered or sometimes rejected when compelling contradictory evidence comes to light. Some scientific explanations are so well established that no new evidence is likely to alter them. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature that is supported by many facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena. A good example is the theory of gravity. After hundreds of years of observation and experiment, the basic facts of gravity are understood. The theory of gravity is an explanation of those basic facts. Scientists then use the theory to make predictions about how gravity will function in different circumstances. Such predictions have been verified in countless experiments, further confirming the theory. Evolution stands on an equally solid foun- dation of observation, experiment, and confirming evidence The Theory of Evolution Has Been Repeatedly Tested and Confirmed We all know from our experience that biological traits pass from parents to offspring. This is the basis of evolution. Sometimes traits change between generations. If a new trait results in an offspring doing bet- ter in its natural surroundings and producing more offspring that also inherit the trait, that trait will become more widespread over time. If the new trait makes the offspring less able to survive and thus leave fewer offspring, the trait will tend to fade from existence. Natural selection is the process by which some traits succeed and others fail in the environment where the organism lives. For every type of life we see today, there were many other types that were unsuccessful and became extinct. Scientists no longer question the basic facts of evolution as a process. The concept has with- stood extensive testing by tens of thousands of specialists in biology, medicine, anthropology, geology, chemistry, and other fields. Discoveries in different fields have reinforced one another, and evidence for evolution has continued to accumulate for 150 years.