news:1103124906.661109.290630@f14g2000cwb.googlegroups.com...
>
> Uncle Davey wrote:
> > > From the article:
> > > --------------------------------------------------------
> > > Snakes in Australia have evolved to counter the threat of invasive,
> > > poisonous cane toads, scientists have found.
> > >
> > > The toads (Bufo marinus) were only introduced in the 1930s but have
> > > already overwhelmed the local wildlife in Queensland with their
> rapid
> > > reproduction and toxic flesh, which kills many predators foolish
> > > enough to make them a meal.
> > >
> > > But for two species of snake, at least, natural selection has
> produced
> > > a defence: the snakes have developed relatively smaller heads and
> > > longer bodies.
> > >
> > > In essence, the reduced gape of the animals limits their ability to
> > > eat the toads likely to do them the most damage.
> > > ---------------------------------------------------------
> > >
> > > Read it at http://news.bbc.co.uk/1/hi/sci/tech/4073359.stm
> > >
> > > But they're still snakes! They haven't evolved into monkeys or
> > > people! ;-)
> > >
> > >
> > > J. Spaceman
> > >
> >
> > In fact, they haven't speciated at all.
>
> No one claimed they did. The authors tested a prediction of the Theory
> of Evolution w/r/t morphological selection and found support.
>
I don't think any serious creationist would take issue with that point.
> >
> > All that happened is that the naturally smallest have survived.
> >
> > Uncle Davey
>
> Nice to see you at least grant the validity of the process of Natural
> Selection.
There is nothing to doubt as to Natural Selection. It is a very clear point
and we can take it as a given.
I have never come on here or anywhere else saying that there is no natural
selection.
I have said there is natural selection and even limited speciation.
>
> Will you tell us, with citation(s) please, what biological barriers
> prevent continued selection pressures from producing speciation?
> - F.
>
Speciation occurs given sufficient iterations of generations at the number
of mutations per million generations at the proportion of mutations which
are likely, given the diversity of the organism's accessible set of
ecosystems at the point at which the mutation occurs to convey a
reproductive advantage and which are able to be passed down by heredity into
the descendents' generations. When this happens so many times as to alter
the different parts of the population so much that when they come together
either there is a cognitive or physical barrier to mating or a genetic
mismatch at some point so that viable offspring are not achieved, then we
can say they have "speciated".
Therefore it all depends on how widespread the animal is over varying
ecosystems, how large it is in relation to its geographical limits, its
typical generational life (the age of a female on average when the typical
representative of the next generation is born, or the weighted average age
of the bearing female) how many representatives of the exit form there are
and the inherent stability of its code.
Depending on these factors "speciation" may occur within a few hundred years
to a few million. Downward speciation from higher organisms to microbes and
protozoa is much quicker than that, and could be days or weeks, but I am
talking about speciation to a similar organism, not HeLa style speciation
which doesn't really go anywhere.
I was making the point that the snake in question has not speciated. Given
another few thousand years it might go on to speciate that way, but I doubt
it will actually get that far.
Uncle Davey
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