Microevolution

Microevolution, broadly defined, is the inevitable small-scale changes in allele frequencies in a population within the same species. Under this broad definition, this change in overall allele frequencies occurs with every birth or death of a member of the species.

Microevolution, narrowly defined, is the unproven theory that natural selection can, over time, transform an organism into a more specialized form within the same species. Lack of evidence for natural selection has led most scientists to use the broad definition above rather than a definition based on natural selection.