microevolution

Microevolution is the occurrence of small-scale changes in allele frequencies in a population, over a few generations, also known as "change below the species level"^[1].

These changes may be due to several processes: mutation, natural selection, artificial selection, gene flow and genetic drift.

Population genetics is the branch of biology that provides the mathematical structure for the study of the process of microevolution. Ecological genetics concerns itself with observing microevolution in the wild. Typically, observable instances of evolution are examples of microevolution; for example, bacterial strains that have antibiotic resistance.

Microevolution can be contrasted with macroevolution, which is the occurrence of large-scale changes in gene frequencies in a population over a geological time period (i.e. consisting of extended microevolution). The difference is largely one of approach. Microevolution is reductionist, but macroevolution is holistic. Each approach offers different insights into the evolution process.

Origin of the term

The term was first used by Harvard-educated botanist Robert Greenleaf Leavitt in the journal Botanical Gazette in 1909, addressing what he called the "mystery" of how formlessness gives rise to form.^[2]

..The production of form from formlessness in the egg-derived individual, the multiplication of parts and the orderly creation of diversity among them, in an actual evolution, of which anyone may ascertain the facts, but of which no one has dissipated the mystery in any significant measure. This microevolution forms an integral part of the grand evolution problem and lies at the base of it, so that we shall have to understand the minor process before we can thoroughly comprehend the more general one...

However, Leavitt was using the term to describe what we would now call developmental biology, it was not until Russian Entomologist Yuri Filipchenko used the terms "macroevolution" and "microevolution" in 1927 in his German language work, "Variabilität und Variation", that it attained its modern usage. The term was later brought into the English-speaking world by Theodosius Dobzhansky in his book Genetics and the Origin of Species (1937)^[1].

Misuse

The term 'microevolution' has recently become popular among the anti-evolution movement, and in particular among young Earth creationists. The claim that microevolution is qualitatively different from macroevolution is fallacious, as the main difference between the two processes is that one occurs within a few generations, whilst the other takes place over thousands of years (i.e. a quantitative difference).^[3] Essentially they describe the same process.

The attempt to differentiate between microevolution and macroevolution is considered to have no scientific basis by any mainstream scientific organization, including the American Association for the Advancement of Science.^[4] Contrary to belief among the anti-evolution movement proponents, evolution of life forms beyond the species level ("macroevolution", i.e. speciation) has indeed been observed and documented by scientists on many occasions.^[5]

See also

• Macroevolution

References

1. ^ ^{a b} Macroevolution: Its definition, Philosophy and History
2. ^ Leavitt, Robert Botanical Gazette 1909 vol.47 no.1 Jan. A Vegetative Mutant, and the Principle of Homoeosis in Plants http://www.jstor.org/pss/2466778
3. ^ Claim CB902: "Microevolution is distinct from macroevolution", TalkOrigins Archive
4. ^ Evolution Press Release American Association for the Advancement of Science
5. ^ Complete sourced list of observed instances of speciation, TalkOrigins Archive

External links

• Microevolution (UC Berkeley)
• Microevolution vs Macroevolution