Lévolution

L'évolution, commonly translated as evolution in English, is the process by which the genetic composition of biological populations changes over successive generations. It explains how heritable traits arise, spread, or disappear in populations, leading to diversity and, over long timescales, the origin of new species. The main mechanisms include natural selection, mutation, genetic drift, gene flow, and recombination. Natural selection acts on heritable variation, favoring traits that improve survival and reproduction in a given environment; mutations provide new variation; genetic drift and gene flow shape allele frequencies, especially in small populations or when populations mix.

Evidence for evolution comes from the fossil record, comparative anatomy, embryology, biogeography, and molecular genetics, as well as repeated observations of speciation in the wild and in the laboratory. The theory spans microevolution (small changes within populations) and macroevolution (larger patterns such as speciation and diversification). The modern synthesis of the 20th century integrated Darwinian natural selection with Mendelian genetics, uniting diverse fields under a common framework.

Common misconceptions are that evolution is goal-directed or that individuals evolve; in fact, populations evolve over generations, and natural selection is one of several mechanisms. L'évolution remains a central concept in biology, guiding research in medicine, ecology, and conservation, and it continues to be refined by genetic and genomic data.