Evolutionary theory is a scientific explanation for how species change over time. It is based on the idea that all species are related and gradually change over time due to genetic variation in a population that affects the physical characteristics of an organism. The theory of evolution by natural selection was first proposed by Charles Darwin and Alfred Russel Wallace in the mid-19th century as an explanation for why organisms are adapted to their physical and biological environments.
Key features of evolutionary theory include:
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Descent with modification: This is the idea that species change over time and that new species arise from existing ones.
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Natural selection: This is the process by which traits that enhance survival and reproduction become more common in successive generations of a population. It embodies three principles: variation exists within populations of organisms with respect to morphology, physiology, and behavior; different traits confer different rates of survival and reproduction; and these traits can be passed from generation to generation.
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Genetic variation: This is the raw material for evolution, and it arises from mutations, gene flow, and genetic drift.
Evolutionary theory is supported by evidence from a wide variety of scientific disciplines, including genetics, which shows that different species have similarities in their DNA. It is one of the best-substantiated theories in the history of science. Evolutionary biologists continue to study various aspects of evolution by forming and testing hypotheses as well as constructing theories based on evidence from the field or laboratory and on data generated by the methods of mathematical and theoretical biology.
