Claim CB928:
Why are beneficial traits not evolved more often? If wings were
beneficial for protobirds, for example, why have they not evolved on
gazelles and apes?
Response:
- Different organisms make their living in different ways, so a trait
that is beneficial for one organism may not be benefical for another.
For example, if the ability to eat a certain kind of hard seed is
beneficial for one bird, it may not be beneficial to another for the
simple reason that the first bird has a monopoly on those seeds
already.
Beneficial traits have drawbacks, too. They usually cost extra energy
to grow and use, and often they have other costs. If a trait's
advantages do not outweigh its disadvantages, it will not evolve. The
existence of an organism that already has the trait often means it is
not worth it for another organism to evolve it.
- Evolution can work only (or almost only; there may be rare
exceptions) by making slight modifications to existing features. Most
of the modifications must be adaptive. If the raw materials for a
trait do not exist, the trait will not evolve even if it is beneficial.
created 2003-7-1
