Recognizing adaptive characters

The study of adaptation could be made foolproof if we had a criterion to distinguish in advance between adaptive and non-adaptive characters.

General rules for recognizing adaptations:

• Adaptations can be recognized as characters that appear to be too well fitted to their environment for the fit to have arisen by chance.

• Adaptations are characters that help their bearers to survive and reproduce.

• Adaptations are purposive and often complex: the sorts of characters that before Darwin would have suggested the existence of God.

There is no doubt that some adaptations, such as the camouflage of stick insects like this mantid opposite, easily fit this definition but there can be problems with doubtful borderline cases: especially problematic, for instance, is the small differences in a character in different species.

Finally, you should be aware that the issue of adaptation is a controversial one in evolutionary biology. The information in this tutorial should provide you with enough background information to follow the arguments, some of which are covered in the classic texts available.

As a taste of this, the biologist Richard Lewontin attacks the entire concept of an adaptation.