Exaptation
In evolutionary biology, exaptation is the use of a property for a function for which it was not originally created - in other words: it is a "misappropriation".
The distinction between function-related adaptation and the assumption of functions (exaptation) alienated from an original purpose by a property previously used differently goes back to the treatise "Exaptation - a missing term in the science of form" by Stephen Jay Gould and Elisabeth Vrba from the 1982. From the concept of exaptation , Gould also distinguished the concept of pre-adaptation (synonym: pre-adaptation), which describes a property that has developed by chance (without a recognizable function) and proves useful under changed environmental conditions.
One example is follicular atresia , which may be an adaptation to maintain the necessary hormonal balance during pregnancy. Menopause would therefore be a consequence of this adaptation without itself being a selected adaptation.
The term exaptation was later used in genetics by Jürgen Brosius and Stephen Jay Gould for the recruitment of previously non-functional areas of the genome into a function.
Due to the proximity of the terms "exaptation" and "pre-adaptation", it was controversially discussed whether an independent concept "exaptation" was necessary to describe the evolutionary processes. The scientific reality is that the terms “exaptation” and “pre-adaptation” are often used synonymously. In any case, it is thanks to Gould to have emphasized the importance of undirected structures for evolution with the term "exaptation" . Many evolutionary biologists today share the view that new structures never emerge specifically for something, but rather arise accidentally as by-products when the genetic material is incorrectly passed on. Because the selection itself does not create new structures, but starts with the existing variants, all new variants must have been created as exaptations. This also fits in with the knowledge that not only those structures are retained that prove to be advantageous, but also those that simply do not disturb further.
literature
- Stephen Jay Gould, Elisabeth S. Vrba: Exaptation - a missing term in the science of form. In: Paleobiology. Volume 8, No. 1, 1982, pp. 4–15, full text (PDF)
- Jürgen Brosius, Stephen Jay Gould: On "genomenclature": a comprehensive (and respectful) taxonomy for pseudogenes and other "junk DNA". In: PNAS . Volume 89, No. 22, 1992, pp. 10706-10710, full text (PDF; 1.2 MB) .
Individual evidence
- ↑ John Sherwood Perry: The ovarian cycle of mammals. Oliver and Boyd, Edinburgh 1971, (= University Reviews in Biology , No. 13).