Blackwell Publishing

Adaptive explanation - Is it always appropriate to describe characters as adaptations?


Flying fish obey the law of gravity

A character of an organism can have beneficial effects that it is not useful to call adaptive. Some consequences follow from the laws of physics and chemistry without any need for shaping by natural selection. The following passage from Williams' book Adaptation and Natural Selection illustrates the point:

"Consider a flying fish that has just left the water to undertake an aerial flight. It is clear that there is a physiological necessity for it to return to the water very soon; it cannot long survive in the air. It is, moreover, a matter of common observation that an aerial glide normally terminates with a return to the sea. Is this the result of a mechanism for getting the fish back into water? Certainly not; we need not invoke the principle of adaptation here. The purely physical principle of gravitation adequately explains why the fish, having gone up, eventually comes down."

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