Microevolution

Biologists have long recognized a distinction between relatively minor changes within a species, which they call "microevolution," and the much larger changes necessary to produce significantly new features, which they call "macroevolution."

Microevolution covers small, distinct changes within a species (as in animal breeding) typically attributable to a single genetic change, while macroevolution refers to a change much larger in scope, such as the proposed evolution of primates into men, or from simple single-celled organisms into complex multi-celled organisms.

Typically, observable instances of evolution are examples of microevolution, for example bacterial strains which have become resistant to antibiotics. Since microevolution can be observed directly, both pro-evolution and anti-evolution groups agree that it is a fact of life.

Creation scientists who do not believe the Theory of evolution have proposed that microevolution always takes the form of destructive genetic mutations, which happen to confer an advantage to individuals in a specific environment. Because macroevolution requires many constructive genetic changes, they argue that microevolution cannot lead to macroevolution. One example of a destructive mutation which conferred a competitive advantage under a specific situation is Streptococcus pneumoniae, some strains of which are resistant to penicillin. But this resistance requires the bacterium to expend extra resources that the non-resistant bacteria do not, and so it does not compete well with them in the absence of penicillin.

See Speciation

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