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Evolution
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Part of a series on
Evolutionary biology
Introduction to evolution
Common descent
Evidence of common descent
Population genetics
Variation • Mutation
Natural selection • Adaptation
Polymorphism (biology)
Genetic drift • Gene flow
Speciation • Adaptive radiation
Co-operation • Coevolution
Divergent • Convergent
Parallel evolution
Extinction
Origin of Life • History of life
Timeline of evolution
Human evolution
Phylogeny
Biodiversity • Biogeography
Classification • Cladistics
Transitional fossil
Extinction event
Overview
Timeline of paleontology
History of paleontology
Renaissance and Enlightenment
Before Darwin
Darwin • On the Origin of Species
Before the Synthesis
Modern evolutionary synthesis
Molecular evolution • Evo-devo
Current research
Applications of evolution
Artificial selection
Bioinformatics
Evolutionary anthropology
Evolutionary computation
Evolutionary dynamics
Evolutionary ethics
Experimental evolution
Ecological genetics
Evolutionary medicine
Evolutionary neuroscience
Evolutionary physiology
Evolutionary psychology
Phylogenetics
Systematics
Theory and fact
Social effect
Controversy
Objections
Level of support
Evolutionary Biology Portal
Category • Related topics • Book
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Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth originated and then evolved from a universal common ancestor approximately 3.7 billion years ago. Repeated speciation and the divergence of life can be inferred from shared sets of biochemical and morphological traits, or by shared DNA sequences. These homologous traits and sequences are more similar among species that share a more recent common ancestor, and can be used to reconstruct evolutionary histories, using both existing species and the fossil record. Existing patterns of biodiversity have been shaped both by speciation and by extinction.Charles Darwin was the first to formulate a scientific argument for the theory of evolution by means of natural selection. Evolution by natural selection is a process that is inferred from three facts about populations: 1) more offspring are produced than can possibly survive, 2) traits vary among individuals, leading to differential rates of survival and reproduction, and 3) trait differences are heritable. Thus, when members of a population die they are replaced by the progeny of parents that were better adapted to survive and reproduce in the environment in which natural selection took place. This process creates and preserves traits that are seemingly fitted for the functional roles they perform. Natural selection is the only known cause of adaptation, but not the only known cause of evolution. Other, nonadaptive causes of evolution include mutation and genetic drift.In the early 20th century, genetics was integrated with Darwin's theory of evolution by natural selection through the discipline of population genetics. The importance of natural selection as a cause of evolution was accepted into other branches of biology. Moreover, previously held notions about evolution, such as orthogenesis and "progress" became obsolete. Scientists continue to study various aspects of evolution by forming and testing hypotheses, constructing scientific theories, using observational data, and performing experiments in both the field and the laboratory. Biologists agree that descent with modification is one of the most reliably established facts in science. Discoveries in evolutionary biology have made a significant impact not just within the traditional branches of biology, but also in other academic disciplines (e.g., anthropology and psychology) and on society at large.
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