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Re: Making Lip of It



2011/9/23 Jaime Headden <qi_leong@hotmail.com>:
>
> I wouldn't be so sure that characteristics such as large canines are _not_ 
> the product of natural selection. Just because the animal is of domesticated 
> stock, not all aspects of siamese breeding is controlled, and deviations 
> (such as Rex hair pattern or the Scottish' fold) can enter into the gene pool 
> without controls, and then become spread through the pool by selective 
> breeding. The mutations in body form, color, etc., can develop and spread 
> without controls in domestic cats due to uncontrollable breeding. Fanciers 
> and professional breeders are not the only method by which the population 
> booms, as my American shorthair/Siamese mix can attest.


A clarification: in the case of the siamese cats, I do not know if it
is a long teeth or a short lip what implies the patter of lip not
covering canines. You are right that natural selection may still act
among domestic animals, most easy to see in the case of severely
disabling genes. In the case of teeth and lips in Siamese cats, and
accepting the possibility of natural selection having something to do
with this condition, I would re-state my opinion is that they cannot
be example of a natural condition evolving by natural selection,
because it may not have arisen by natural selection.

That said, I am skeptical of the powers of natural selection in the
generation of the physical features in the case of cats. I think
natural selection may in any case be more powerful in the case of
alley or feral cats than house cats. For reproduction of house cats is
partially controlled by humans, which, if out of fashion like some
kind of curly hair or ears, will selectively breed. It seems that
reproductive potential of house cats is very secondarily affected by
their selective advantages, with human will (birth control pills and
emasculation) being important factors diminishing the reproductive
possibilities of ordinary or out of fashion cats relative to fashion
varieties, thus providing other mechanism for increase of proportions
of new varieties. The influence of human hand in house cat
reproduction suggests to me that natural selection finds here powerful
opposition. Human caprice can also influence the change in variety
proportions in alley and also feral cats, because many kittens borning
from house cats which cannot find a home now form part of these
groups. That human hand is behind the increase of proportion of
fashion or new varieties may be attested by the fact that you can see
a larger proportion of new varieties in rich countries (along with a
greater proportion of exotic pets), with humans being more capable to
buy expansive fashion varieties, than in poor countries, where kittens
are mostly donated because most people will not pay for an ordinary
cat, and can't afford an expensive one (and thus fashion or new
varieties keep being uncommon).

Regarding Jason's point, you are right that mammalian lips seem not a
huge obstacle to teeth penetrating prey, because of being soft enough.
However, if we accept carnivorous dinosaurs as having scales in their
lips, lip flexibility would at least partially depend on the size of
the scales. If bird beaks have something to do with reptilian scales
after all, and if dinosaurs had similarly large scales, they would
make their lips relatively less flexible, and lip scales would be
prone to breaking as the teeth penetrated flesh. Now, if dinosaur lips
possesed small scales, or lacked scales (one of these two would apply
to crocodiles, after all), you would be right.