Published Online: 15 FEB 2012
Copyright © 2001 John Wiley & Sons, Ltd. All rights reserved.
How to Cite
Levinton, J. S. 2012. Macroevolution: Overview. eLS. .
- Published Online: 15 FEB 2012
Macroevolution is the sum of a range of processes that explain evolutionary changes that resulted in the diversity of major body plans of living organisms through geological time and at present. The field addresses the origin of major taxonomic groupings, the causes of evolutionary radiations, major biogeographic patterns and large-scale extinctions. A diversity of approaches are required, including a firm understanding of the evolutionary relationships of the major branches of life, a geological context including good estimates of time and environment, accurate estimates of biological diversity through time and space, a complete study of the genetic and developmental mechanisms and processes that lead to the diversity of form of life, and an understanding of major episodes of origin and extinction in the history of life. Studies of genetic and developmental function have revealed the pattern and order of determination of form and the genetic variation that may matter in major evolutionary transitions. Our continuing refinement of the geological record has demonstrated coordinated origins or evolutionary radiations and mass extinctions. Characterisation of ancient climate, atmospheric and oceanic conditions, and palaeogeography have led to a better understanding of the likely mechanisms causing mass extinctions and to a lesser extent evolutionary radiations.
New approaches using genomic and DNA sequencing tools have produced much more accurate evolutionary trees that give us a context to explain the mechanisms of evolutionary transition.
The understanding of the cellular and genetic expression mechanisms of development has given us a large-scale context to identify evolutionary transitions.
Form variation among major groups has to be understood in terms of evolutionary history, major adaptive constraints on form and to some extent by constraints on form that arise from limited variation of developmental mechanisms. The power of natural selection has been verified even with this larger-scale approach.
Palaeontologists have devoted a great deal of effort to understanding whether speciation is an important component of evolutionary change and in sampling fossil populations at a finer scale.
On the larger scale, the fossil record shows strong fluctuations in diversity over time, but is especially organised by major coordinated evolutionary radiations and a few mass extinctions.
- fossil record;