Evolution: A Very Short Introduction (Very Short Introductions) by Charlesworth Brian & Deborah Charlesworth

Author:Charlesworth, Brian & Deborah Charlesworth [Charlesworth, Brian]
Language: eng
Format: mobi, epub
Publisher: Oxford University Press
Published: 2003-06-25T16:00:00+00:00

To illustrate selection of an advantageous mutation, consider the arms race between humans and rats, in which we try to develop rat poisons, and rats evolve resistance. The rat poison warfarin kills rats because it prevents blood clotting. It binds to an enzyme needed in the metabolism of vitamin K, which is important for blood clotting and many other functions. Resistant rats were once rare, because their vitamin K metabolism is changed, reducing growth and survival. In other words, there is a cost of resistance. In farms and towns where warfarin is used, however, only resistant animals can survive, so there is strong natural selection, despite the cost. The resistant version of the gene has therefore spread to high frequencies in the rat population, though the cost keeps it from spreading to all members of the species. However, a recent development is the evolution of a new kind of resistance which seems to be free from the cost, and which may even be advantageous (in the absence of poison). There is thus continued evolution in response to a change in the rats’ environment.

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