Evoluionism

Evoluionism, often spelled evolutionism, denotes the theory that species arise and change over time through heritable variation and differential survival and reproduction. In scientific use, the terms evolution or the theory of evolution are standard; evolutionism is more common in historical, philosophical, or cultural discussions of evolutionary ideas.

The core of evolution theory holds that all living beings share a common ancestry and that populations change over generations via mechanisms such as natural selection, genetic drift, mutation, gene flow, and recombination. Descent with modification explains how new species can arise from ancestral populations, and speciation occurs when diverging lineages accumulate enough differences to become distinct.

Evidence for evolution comes from multiple lines of inquiry. The fossil record shows gradual, branching changes in organisms over time. Comparative anatomy and embryology reveal patterns of similarity among related groups. Biogeography documents the distribution of life in patterns consistent with common descent. Modern genetics and genomics provide direct confirmation of shared ancestry and the mechanisms of inheritance, including the universal genetic code and molecular phylogenies.

Historically, ideas about evolution emerged before Darwin, with early concepts by scientists such as Jean-Baptiste Lamarck. Charles Darwin and Alfred Russel Wallace proposed natural selection as a primary engine of evolution in the 19th century, leading to the modern synthesis in the 20th century that integrated genetics with natural selection. In contemporary science, evolution is a central unifying concept in biology, supported by extensive evidence; in some regions, debates with creationism or intelligent design continue, but the scientific consensus remains robust.