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Evolution of Dogs

 
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jabailo



Joined: 20 Mar 2006
Posts: 1273
Location: Kent (East Hill), WA

PostPosted: Tue Mar 01, 2011 2:56 pm    Post subject: Reply with quote

One of the examples of evolution in practice that Dawkins uses is dog breeding. He compares the selection of man to emphasize features in the dog as similar to that of natural selection. Eventually, the Schnauzer and the Great Dane become so structurally incompatible that they end up being the beginning of a new species. I proposed these experiments with regard to dog breeding to see if its really true...are we seeing speciation or just selection without any permanent result:

1. Without human intervention do dog breeds return to the original species

2. Take all dog breeds...can the be divided into groups that cannot physically breed?

3. Let dogs breed among these prototypically compatible groups. do the dogs revert to the founder or create a new species?

4. Do mutts in the wild revert to the original species? Is it really true that mutts are "hardier" than pure "breeds"?

5. has a "breed" ever been created that is genetically sterile with other dogs?
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brian-hansen
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PostPosted: Wed Mar 02, 2011 12:41 pm    Post subject: Reply with quote

I haven't read Dawkin's text on breeding dogs, so I could be missing some
key ideas in your post. That said, and with the hope of not causing offense,
the posting of your "experiments" has a kind of naive quality to it.

Since you use the past tense, apparently you've proposed these
experiments elsewhere. If not, the "naive quality" I mentioned is
amplified, as if you were writing 100 years ago, or more, and nothing
was known about these topics. It is as though you think you are advancing
science in new directions, when , in reality, you are expressing your
lack of knowledge, and hoping that others more knowledgeable will
come along, and correct your misconceptions and fill in the gaps
of your knowledge. As is often the case, naivete is perceived as hubris.

As it turns out, I am not the expert you seek, and don't have
the best kinds of answers to give you, though I'm willing to give it a try.
Meantime, the best answer seems to be that maybe you should just
go ahead and read another book.


========

1. Without human intervention do dog breeds return to the original species ?

Dogs do plenty of breeding without human intervention. As
such, the offspring of dogs are subject to natural and artificial
selection. So, with or without artificial selection, evolution would
continue to occur, which means a slow accumulation of small changes.
Dog breeds would not return to their original form,
although they might come to resemble that form superficially.
The question has extra muddling factors: (1) dog breeds *are* of
their original species, so far as we know, (2) there *is* a tendency
to "revert to the mean" as far as the characteristics of offspring
are concerned, but this is not the same thing.



2. Take all dog breeds...can the be divided into groups that cannot physically breed?

The most germane definition of species is whether interbreeding is
possible. If not, then 2 creatures are considered to be 2 different species.
I recast your question, then, as "is there more than one species
of dog?". So far as I know, the answer to this is no.

Your question again seems to have several muddling elements to it.
Could a Chihuahua even reasonably attempt to impregnate a large
dog like a Saint Bernard? And could a female Chihuahua carry a
Chihuahua-Bernard mix? From what I can tell, a) if left alone, at the
right time, they will attempt to mate, and b) the size of the offspring
is regulated by the mother. The answer as it appears to me after
just a few minutes of research is that generally, they can
"physically breed".


3. Let dogs breed among these prototypically compatible groups. do the dogs revert to the founder or create a new species?

The most likely outcome of this situation is: neither.

Speciation is mostly associated with a group being isolated from
other groups of the same species. Dog speciation *could* occur,
but not particularly a result of breeding among what you call the
prototypically compatible groups. Meanwhile the population of
dogs will be incorporating small mutations as time (long long time)
goes by. There would be no genetic "reversion", though it is possible
that there might be the appearance of this, superficially.


4. Do mutts in the wild revert to the original species? Is it really true that mutts are "hardier" than pure "breeds"?

So far as we know, contemporary dogs *are* of the original species.
There is no need to think of them as "reverting". Meanwhile, to my
way of understanding it, "reversion" is not so clear a concept for thinking
about evolution. Yes, as in all chance operations, there is a tendency
to "revert to the mean", but we know since Mendel, that offspring
aren't averages of their parents in their features, but embody
particular choices of alleles. One other sense of the term "reversion"
could be possible. a mutation that was selected against, could
eventually, or immediately be eliminated from the dog population's
genes. You could say, I guess, that the dog population "reverted"
back to the pre-mutation stage, but other mutations are going to
continue. "Reversion" is not a great category of thinking to use when
considering evolution, in my opinion.

One muddle in this case is that it is
trickier to talk of ancient animals' ability to mate with contemporary ones.
The simple notion of species breaks down, and we do not have the
technology to categorize these 2 groups precisely.

4(b). Yes, it is generally true that mixed breeds are hardier. By doing
a lot of inbreeding, small mutations that are harmful to fitness
lose the corrective potential of a different allele choice.


5. has a "breed" ever been created that is genetically sterile with other dogs?

This is another way of saying are there different dog species.
It is my understanding that the answer is no. There is only one.
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jabailo



Joined: 20 Mar 2006
Posts: 1273
Location: Kent (East Hill), WA

PostPosted: Mon May 16, 2011 9:33 am    Post subject: Reply with quote

I won't take on all your arguments full force at this point, but I will mention a story I saw on the news about new "hybrid-pure" dogs where they are mating two traditional characteristic, but divergent, pure breed dogs (bulldogs and whippets) to "breed out" unfavorable characteristics (like the bulldog's too short snout that causes it to have tongue and breathing problems).

In the words of the reporter, they are turning them back into mutts!
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jabailo



Joined: 20 Mar 2006
Posts: 1273
Location: Kent (East Hill), WA

PostPosted: Fri Mar 02, 2012 3:49 pm    Post subject: Reply with quote

Evolution: A View from the 21st Century (FT Press Science)
by James A. Shapiro

Quote:
It is important to note that selection has never led to formation of a new species, as Darwin postulated. No matter how morphologically and behaviorally different they become, all dogs remain members of the same species, are capable of interbreeding with other dogs, and will revert in a few generations to a common feral dog phenotype if allowed to go wild. The way we make new species synthetically is by interspecific hybridization.


https://kindle.amazon.com/work/evolution-century-press-science-ebook/B0050O8YNG/B0054KOKZ2
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