[Taxacom] (no subject)

[Michael Heads]

Rob,
Genetic trends and selection both always exist together. Selection can have
some effect, changing local frequencies and so on. But it doesn't explain
the long term trends, e.g. reduction and fusion in the vertebrate skull or
angiosperm flower, that persist over tens of millions of years in very
different environments. The trends can be quite simple in morphological
terms and so the new work emphasizing the significance of mutation in
general and non-random mutation in particular could be relevant.

Michael

On Thu, Mar 7, 2013 at 9:07 PM, Rob Smissen <SmissenR at landcareresearch.co.nz
> wrote:

> Hi y'all
>
>
>
> I think Micahael is quite correct that hair on snails or any other trait
> of an organism might have nothing to do with any purpose/end/advantage. And
> I agree whole heartedly that genomic change is not well modelled as random,
> and that genetic polymorphism is not unlimited and unconstrained.
>
>
>
> However, I do think that selection plays an important role in determining
> which polymorphisms (however they arise) are maintained within populations.
>
>
>
> Michael are you arguing that all evolution is the result of prior trends
> in genomes unmediated by selection, the majority, or just some stuff here
> and there?
>
>
>
> cheers
>
> Rob
>
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