Macroevolution

This article draws out the major philosophical issues that underlie macroevolution. This term means evolution that takes place at or above the level of the species. On the basis of the observation of fossil records, the history of life, and current biological populations scientists have concluded that organisms and taxa are unevenly distributed in space and time. Steven Stanley proposed the principle of species selection which states that species-level evolution occurs via a process on a different hierarchical level than microevolution and may or may not involve characteristics that are emergent. Many implications are drawn from the relation of extinction to macroevolution. Firstly, extinction alters the normal course of evolution not determined by previous selective criteria. Secondly, mass extinction can rapidly introduce new environmental conditions and thus new selective criteria. Finally, extinction theory implies that macroevolution may not be related to the biological processes of microevolution.