Hoppe, R.

The meaning of function statements is not clear. Several authors have come up with different explications. By interviewing biologists I tried to get a picture of how they think about 'function'. Two explications of "Feature X of organism S has function F" came to the fore: (1) "X contributes to F and F contributes to survival/reproduction of S" and (2) "X does F and that contributes to the evolutionary development of X in S via natural selection". Most biologists also related function to adaptation. Gould and Vrba criticize the ordinary use of 'adaptation' in biology. They propose to use it only in the sense of features developed by natural selection for their current role and to use 'exaptation' for features enhancing fitness, but not developed for this by natural selection. This, however, leaves a terminological gap, because as a consequence only effects of adaptations are functions. Effects of exaptations and effects which are not beneficial, like the production of heart sounds, are placed on the same level. That is not in accordance with the practice of biology. That is why a distinction is made between general, adaptive and exaptive functions: function as a pluralistic concept.