Macroevolution

Macroevolution is the suite of evolutionary changes that accumulate above the level of species, leading to new genera, families, or higher taxa, as well as large-scale patterns in biodiversity and morphology. It encompasses speciation, extinction, evolutionary trends, the emergence of major body plans, and broad shifts in the distribution and diversity of life over geologic time. Although macroevolution is often described as distinct from microevolution, it is driven by the same underlying processes—mutation, natural selection, genetic drift, and developmental constraints—acting over long time spans.

Macroevolutionary patterns include adaptive radiations, where a lineage rapidly diversifies into multiple ecological roles; punctuated equilibria or long periods of relative stasis followed by rapid change; and major transitions in individuality, such as the origin of multicellularity or vertebrate skulls and amniotes. The tempo and mode of macroevolution have been debated, ranging from gradualism to punctuated equilibria.

Evidence comes from multiple sources: the fossil record, comparative anatomy and embryology, molecular phylogenies, and developments in evo-devo. These data reveal speciation events, lineage branching, and correspondence between morphological change and ecological opportunity, as well as instances of convergent evolution across distant groups.

Examples of macroevolutionary outcomes include the origin of major animal groups (e.g., the evolution of tetrapods from fish, amniotes from amphibian-like ancestors), the rise of mammals after the dinosaur extinction, and large-scale patterns in biodiversity through the Phanerozoic. Mass extinctions and continental rearrangements have also shaped macroevolution by opening ecological space for diversification.

In modern studies, macroevolution is analyzed with phylogenetic methods, molecular clocks, and mathematical models to infer rates of speciation and extinction, as well as to test ideas about rates, trends, and drivers.