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Exaptation (a replacement for the teleologically-loaded term "pre-adaptation") and the related term co-option describe a shift in the function of a trait during evolution. For example, a trait can evolve because it served one particular function, but subsequently it may come to serve another. Exaptations are common in both anatomy and behaviour. Bird feathers are a classic example: initially they may have evolved for temperature regulation, but later were adapted for flight. Interest in exaptation relates to both the process and products of evolution: the process that creates complex traits and the products (functions, anatomical structures, biochemicals, etc.) that may be imperfectly developed. ==History and definitions== The idea that the function of a trait might shift during its evolutionary history originated with Charles Darwin (). For many years the phenomenon was labeled "preadaptation", but since this term suggests teleology, which is contrary to a basic principle of natural selection, it has been replaced by the term exaptation. The idea had been explored by several scholars〔See Jacob (1977) and Mayr (1982) for references.〕 when in 1982 Gould and Vrba introduced the term "exaptation". However, this definition had two categories with different implications for the role of adaptation.
The definitions are silent as to whether exaptations had been shaped by natural selection after cooption, although Gould and Vrba cite examples (e.g., feathers) of traits shaped after cooption. Note that the selection pressure upon a trait is likely to change if it is (especially, primarily or solely) used for a new purpose, potentially initiating a different evolutionary trajectory. To avoid these ambiguities, Buss, et al. (1998) suggested the term "co-opted adaptation", which is limited to traits that evolved after cooption. However, the commonly used terms of "exaptation" and "cooption" are ambiguous in this regard. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「exaptation」の詳細全文を読む スポンサード リンク
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