adaptation

[John Grehan]

John Trueman wrote

 adaptation is a name we give to the result of an episode of natural
selection.

If this is taken as the definition then one gets into a problem of
demonstrating
natural selection was the cause of a particular feature in the past. What
usually
happens is that a feature is recognized as having some functional role in an
organism's survival. Such features are treated as having been an "advantage"
in some way, and therefore are "adaptations" even though natural selection as
the cause cannot be demonstrated. There may be some other approaches, but this
seems to be the general pattern. If the above defintion were to apply there
would be very few features that could be described as adaptations.

 And a host of molecular mechanisms have been described.
>Natural selection is NOT the only known explanation for EVOLUTION.

Agreed! But the way evolution is taught (at least as I have seen it) often
natural selection is treated as the only mechanism for the evolution of new
biological systems while other mechanisms seem to be restricted to minor
influences such as genetic drift. But I recognize that the field is vast,
and I can miss the boat. If my characterizations are inaccurate or unfair I
would rather know. I would be interested to know what JohnTrueman was
referring to for a  "host of molecular mechanisms" and what evolution
textbooks
have covered the evolutionary role and influcence of these mechanisms that
do not involve natural selection. When
writing on concerted evolution and molecular drive I did not come across
evolution text books that directed serious attention to the process and its
implications, but this may refelect an inadequate literature search.


John Grehan