Macroevolution is a scale of analysis of evolution in separated gene pools.^[1] Macroevolutionary studies focus on change that occurs at or above the level of species, in contrast with microevolution,^[2] which refers to smaller evolutionary changes (typically described as changes in allele frequencies) within a species or population.

The process of speciation may fall within the purview of either, depending on the forces thought to drive it. Paleontology, evolutionary developmental biology, comparative genomics and genomic phylostratigraphy contribute most of the evidence for the patterns and processes that can be classified as macroevolution. An example of macroevolution is the appearance of feathers during the evolution of birds from theropod dinosaurs.

Although the occurrence of macroevolution is overwhelmingly accepted by the scientific community, a tiny minority of scientists dispute its factuality or degree of occurrence.^[3][4] This minority view is often associated with the anti-evolution position of certain religious groups which attempt to differentiate between microevolution and macroevolution, asserting various hypotheses which are not considered scientific by scientific organizations such as the American Association for the Advancement of Science^[5]. See intelligent design or creation myths for more information on these views.

Origin of the term

Russian entomologist Yuri Filipchenko (or Philipchenko, depending on the transliteration) first coined the terms "macroevolution" and "microevolution" in 1927 in his German language work, "Variabilität und Variation"^[6].

Since the inception of the two terms, their meanings have been revised several times and even fallen into disfavour amongst scientists who prefer to speak of biological evolution as one process.^[6]

Macroevolution and the modern evolutionary synthesis

Within the Modern Synthesis school of thought, macroevolution is thought of as the compounded effects of microevolution. Thus, the distinction between micro- and macroevolution is not a fundamental one - the only difference between them is of time and scale. However, it should be noted that time is not a necessary distinguishing factor - macroevolution can happen without gradual compounding of small changes; whole-genome duplication can result in macroevolution occurring over a single generation. One of the most significant applications of this is found in the evolution of the vertebrates, which was mediated by duplications of the hox gene complex.

Research topics

Some examples of subjects whose study falls within the realm of macroevolution:

• The debate between punctuated equilibrium and gradualism
• Speciation and extinction rates
• Mass extinctions
• Adaptive radiations such as The Cambrian Explosion
• Changes in biodiversity through time
• The role of development in shaping evolution, particularly such topics as heterochrony and developmental plasticity
• Genomic evolution, like horizontal gene transfer, genome fusions in endosymbioses, and adaptive changes in genome size

Criticisms of macroevolution

The term "macroevolution" frequently arises within the context of the evolution/creation debate, usually brandished by creationists alleging a significant difference between the evolutionary changes observed in field and laboratory studies and the larger scale macroevolutionary changes that scientists believe to have taken thousands or millions of years to occur. They may accept that evolutionary change is possible within species ("microevolution"), but deny that one species can evolve into another ("macroevolution").^[1]

These arguments are rejected by mainstream science, which holds that there is ample evidence that macroevolution has occurred in the past.^[6][7] The consensus of the scientific community is that the alleged micro-macro division is an artificial construct made by creationists and does not accurately reflect the actual processes of evolution. Not surprisingly, evolutionary theory (including macroevolutionary change) remains the dominant scientific paradigm for explaining the origins of earth's biodiversity. Its occurrence, while controversial with the public at large, is not disputed within the scientific community.

While details of macroevolution are continuously studied by the scientific community, the overall theory behind macroevolution (i.e. common descent) has been overwhelmingly consistent with empirical data. Predictions of empirical data from the theory of common descent have been so consistent that biologists often refer to it as the "fact of evolution".^[8][9]

Nicholas Matzke and Paul R. Gross have accused creationists of using "strategically elastic" definitions of micro- and macroevolution when discussing the topic.^[1] The actual definition of macroevolution accepted by scientists is "any change at the species level or above" (phyla, group, etc.) and microevolution is "any change below the level of species." Macroevolution, by the definition commonly used by creationist critics, cannot be attained. They describe any observed evolutionary change as "just microevolution".^[1]

See also

• Transitional fossil
• List of transitional fossils

References

External links

• Introduction to macroevolution on the Understanding Evolution website
• Macroevolution as an independent discipline: Macroevolution in the 21st Century
• Macroevolution as the common descent of all life: "29+ Evidences for Macroevolution"
• Macroevolution FAQ

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