Claim CB950:
Evolution says that complex structures would not be formed without a
selective advantage for them. But overspecialization with no adaptive
value sometimes occurs. An example is the enormous antlers of the Irish
elk. Despite the seeming disadvantages, animals with such extreme
features seem to do as well as other animals.
Source:
Macbeth, Norman, 1971. Darwin Retried. Boston: Delta, pp. 70-73
Response:
- There are no established cases of overspecialization that did not have
adaptive value. In some cases, the adaptive value may not be obvious,
but there are none where its absence is plausible. In particular,
sexual selection can produce exaggerated and seemingly detrimental
features, such as the stalks of stalk-eyed flies and the huge antlers
of Irish elk.
- Adaptation can become non-adaptive overspecialization when the
environment changes. If a flower becomes dependant on one pollinator,
for example, the loss of the pollinator can cause the extinction of the
flower.
created 2003-7-28, modified 2004-3-1
