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Re: primers




"Jaime A. Headden" wrote:
> 
> Dann Pigdon (dannj@alphalink.com.au) wrote:
> 
> <Nonsense. Why this constant dichotomy between 'human' and 'natural'?
> Humans are a species that evolved naturally, therefore anything they do
> that provides selective pressure to other species is just as natural an
> evolutionary process as climate change (or any other non-human process).>
> 
>   It's not about introduction of species, or migration, or expansion, or
> habitat loss of an already existing species, but about species
> _formation_, such as allopatry or sympatry. As an example, if a breed of
> dog, say a pug, were out in the wild, would it be selectively breeding
> with pugs? would the pug breed arise naturally?

Again - term like 'out in the wild' and 'naturally', as if what humans
do and what the rest of 'nature' does is in direct opposition. Humans
are a species like any other - anything they do to other species or the
environment is just as natural as anything any other species does.

Pugs arose in a symbiotic relationship with humans who find their form
appealing. Hence they are now well adapted to their particular
ecological niche. For a pug to leave said niche (ie. human habitation)
to go live elsewhere away from humans would be like a polar bear
attempting to take up residence in the tropics, or a fig wasp trying to
make a living without fig trees.

> Feral dogs, horses, cats,
> cattle, goats, etc., tend not to select for breed when mating, and this
> only underscores the lack of utility in using artificial "species" as
> examples of speciation.

Again, you use the biased word 'artificial'. It is sometimes defined as
"not arising from natural growth or characterized by vital processes",
as if what humans do isn't natural for some reason. Secondly, I wouldn't
consider many domesticated breeds to be 'species' in any way. Dogs are
all still the one species. Given enough time domestic breeds may well
speciate, although it'd probably take more than just 10,000 years or so.
Although aren't cattle considered as two species (Bos domesticus &
B.indicus)? Did they have a common ancestor when first domesticated (ie.
are they both derived from Aurochs)?

Feral species very much form their own breeds. Domestic pigs are quite
different in form to their feral cousins here in Australia. Domestic
pigs have found a good ecological niche in which they thrive in great
numbers (namely, a symbiotic relationship with a primate species). In
order to maintain that symbiotic relationship, they must retain the
characteristics that make them useful to humans. Humans are the
selective pressure that maintains the symbiosis, yet in a way domestic
animals also influence our behaviour. Human herders must live in certain
ecological areas in order for the domestic animals to survive.
Eventually selective breeding may alter a species to broaden it's
ecological range, that benefits both domestic species and humans.

Feral pigs in Australia all look much the same, since living apart from
humans provides different selective pressures on behaviour and body
form. After a few generations of this new selective pressure, domestic
pigs begin to look quite different. Domestic and feral pigs are
different breeds, not different species. Hence the physical form of
feral pigs can be considered another breed of pig, therefore in a way
feral animals DO select for breed.

> ...a small animal with
> trouble breathing would not be a fit hunter, and thus may not live long
> enough to breed, or be incapable of protecting or rearing young, so the
> American bulldog, pug, and persians are largely "bad" breeds.

They would be bad if these breeds lived apart from humans. But they
don't, and since humans find these 'bad' characteristics attractive (for
some twisted reason), those 'bad' features are actually to the breeds'
benefit. Vicunas are unable to leave their mountain homes because at
lower altitudes they will have a stroke and die. For vicunas trying to
live at sea level, this characteristic would be considered 'bad'. Yet
they don't live at sea level, so they manage to live with their design
flaw by inhabiting a particular niche. 

>   Human breeding in cattle resulted in destruction of habitat for the sake
> of breeding the cattle as grazers, open range grazers for most varieties,
> and thus the destruction of other ecological niches. Cattle, on the other
> hand, occupy only two, maybe four, niches, given the geography (Indian
> cattle tend to be more forested along with other South-Asian types than
> African, American, and European/West/North/Central-Asian breeds).

That 'destruction' can be seen as beneficial to some species. Animals
that thrive on grasslands (kangaroos and emus, as Australian examples)
benefit from the destruction of rainforest. Plants capable of growing in
compacted soils will have a selective advantage over other plants. One
species' destructive force is another's serendipity.

Cattle now live in places and in numbers that would have been impossible
before humans provided selective pressure. In turn, the cattle allow
humans to live in areas they formerly wouldn't have survived in (or only
with difficulty). Both species have benefitted, although to the
detriment of other species who have had difficulty adapting to the new
conditions. I believe that's a little thing called evolution. :)

-- 
___________________________________________________________________

Dann Pigdon
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://heretichides.ravencommunity.net/
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