In article <10771 at raven.ukc.ac.uk> mjg5 at ukc.ac.uk (ShereKhan) writes:
>>Thanx a lot for your follow-up. I think you are right that evolution
>hasn't stopped, even if I do contradict my former attitude. I guess it is
>evident that maybe Man is the only cause of the evolutionary processes now?
>What I mean is, I feel that evolution that occurs now (such as the tuna
>size) are through a result of artificial selection due to human influence.
>Another example may be isolation of species after the construction of
>highways, rather than the drifting apart of islands. Maybe this human
>influenced evolution is a much faster process and so results in only
>elementary changes like colour or size, rather than more radicle morphological
>adaptations that have arisen over the millions of years. (?)
Nope...go back to Darwin. Look at what is needed for selection. All mponents
are still th For natural selection all you need is superior reproduction
or survival of any genetic variant in whatever environment. There is no goal
or pinnacle to be reached in this process. It has been described as "mech-
anical" like gravity (see Futuyma for a good basic ref.). Since there is
mutation, there will be variation. Evolution just is.
As for human influence, I think that the Tuna case as with most species that
are "preyed" upon by humans for whatever reason is only a minor fraction of
the impact that humans MAY be having on evolution (in terms of speciation).
Instead of speeding up evolution (in terms of speciation), I would think
that humans are doing the reverse by destroying haitats. Differentials in
habitats provides different environments that allow for exploitation of the
various "niches" by different genetic variants (sticking to the above termin-
olgy). If isolated (not to be starting a mechanisms of speciation debate)
from each other long enough, the different variants will adapt to there local
environments andfollow their own evolutionary path until....viola..2 species
from 1. Variaety in habitat thus promotes speciation. Of course the mechanisms
involved are a bit more complicated, but the basics aren't hard to understand.
I hope this helps a bit.