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Originally posted by Renegade The amount of genetic mutation that would be required for a dog to give birth to offspring that - in a single generation - was genetically distinct enough to be classified as a separate species from it's mother is, in practice, prohibitively impossible. A fetus with that degree of damage to its DNA won't get past the earliest stages of development.

Of course you are wrong here but your argument holds some validity. Yes we look at the population as the smallest unit of evolution but its a gradual process. At some point that species of dog will be significantly different enough to not be a dog anymore or simply people will choose not to call it a dog anymore. Although a dog is a silly example since its domesticated, replace dog with a wild animal and thats my argument. You also forget about hox genes as well, with regards to fetus not being able to develope. Over one generation a fly can go from 2 wings to 4 wings by a single mutation.

Speciation is all semantics. One chooses to call a species a different species depending on several things. Location, behaviour, morphology etc. Species of animals and plants crossbreed at times to give new species (its not common but it does happen).

Lets look back to the chicken and the egg arguemnt. At one point the egg will be laid by a bird and in that egg there will be a "proto-chicken" that will diverge from i ts parental birds or have slight genetic differences that will allow it to be classified as a seperate species over time and generations.

so the egg obvoiusly came before the chicken.

once again speciation is semantics. homosapien idaltu and homosapien sapien could have probably interbred. there is speculation that even neanderthal man and homo sapiens interbred. This could mean we are a cross bread.

We look at domestic dogs (who all originated from the grey wolf if im not mistaken) and see a huge morphological difference in all the "breeds". Since this is an issue of "non" natural selection and forced selection implemented by humans, we say that this is not speciation. If we look at dogs in more detail and presume lets say, the environment sought it fit for grey wolfs to diverge into chiwawas on one end and german sheppards in another end, we would have 3 different species classified. In reality we simply have 2. Canis lupus (Wolf) and canis familiaris (shepphard and chiwawa). This is since domestic dogs are manipulated through "dog eugenics" to create breeds while most animals rely on the environment (natural selection) to impose what we call "speciation" through random mutations and traits best suited for the environment at the time.

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Originally posted by Nrg2Nfinit homosapien idaltu and homosapien sapien could have probably interbred. there is speculation that even neanderthal man and homo sapiens interbred. This could mean we are a cross bread.

I've seen many of the ones closely related to the neanderthal in the remote mountains of N.C.

(good post by the way)

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Originally posted by Renegade Lupine and canine are classified as distinct species because in a natural environment they will not choose to breed. Whether they are capable of it or not is something I'm not sure I really want to think about.

So this is how its done. For example, a chihuahua and a British mastiff (pictured) do not choose to mate, or cannot mate. So they can be said to be different species, but both descended from a common ancestor, the wolf. It doesn't happen over one generation, but many, until finally, they are so distinct from each other, they are different species of dog. But they are still dogs. Just different species of dog.

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Originally posted by Nrg2Nfinit Of course you are wrong here but your argument holds some validity. Yes we look at the population as the smallest unit of evolution but its a gradual process. At some point that species of dog will be significantly different enough to not be a dog anymore or simply people will choose not to call it a dog anymore. Although a dog is a silly example since its domesticated, replace dog with a wild animal and thats my argument.

Of course, but that won't happen in a single generation which is what Krypton was asking about.

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You also forget about hox genes as well, with regards to fetus not being able to develope. Over one generation a fly can go from 2 wings to 4 wings by a single mutation.

Hox genes are fairly unique so far as developmental genes go, but even then I'm fairly sure that some random mutation within them will generally destroy the embryo in the very early stages of development, rather than producing the neat, functional morphologies sometimes produced in the fruit flies. I'm sure I can remember reading about experiments on mice to this effect and the embryo simply refused to develop past a certain point, rather than producing a mouse with extra body segments and eight legs or something.

But I think we're in agreement on just about everything else.

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Originally posted by Krypton So this is how its done. For example, a chihuahua and a British mastiff (pictured) do not choose to mate, or cannot mate. So they can be said to be different species, but both descended from a common ancestor, the wolf. It doesn't happen over one generation, but many, until finally, they are so distinct from each other, they are different species of dog. But they are still dogs. Just different species of dog.

As humans we're inclined to try to categorise things into neat, fixed, universal categories, but species don't really lend themselves to such neat divisions, which is why there is still debate in the biological communities about how to formally distinguish one species from another. Generally, a species is defined as a closed gene pool (a group of organisms who produce only with themselves) but this generally requires some sort geographical isolation first: the genetic isolation comes later.

So take Darwin's finches for instance. They all share a common ancestor but the sort of isolation that islands provide means that the populations gradually become genetically distinct (as a consequence of natural selection - different traits will be selected for on different islands - and random genetic drift). If, somehow, these geographical constraints were to be removed (if, maybe, the ocean levels were to sink) the gene-pools of these populations would no longer be isolated. Depending on just how genetically distinct these populations had become, even with the removal of geographical boundaries they either:

a) May not be capable of breeding.
b) May be capable of breeding but may elect not to (sexual selection).

In either of these cases, we would still have no trouble classifying the finches as being of distinct species. If, however, the geographical boundaries were removed and they did begin to interbreed, then the gene-pools could no longer be said to be closed and they would merge to form some new gene-pool in which rare, non-adaptive alelles (which gave the species their unique traits while on separate islands) would gradually disappear. What this demonstrates is that the concept of a species is entirely contingent on exogenous circumstances (in this case geographical isolation) and when these contingencies are removed, the concept of species becomes increasingly blurred.

The case of dog breeds, as Nrg mentioned, is slightly different because this is a case of artificial selection in which mates have been chosen for the animals rather than the animals choosing for themselves. You probably wouldn't get the sort of morphological divergence you get between a chihuahua and a mastiff in nature over so quick a time-scale. I suspect that the genetic difference between the two would be relatively small so breeding would technically be possible, but I'm not sure if they would ever choose to. As I said, though, it's something of a moot point because the kind of genetic trajectories they've come from are of an entirely artficial contruction and could not have conceivably occurred in a state of nature.

Very good post renegade, i think you summed up things nicely. Reading back to your original post it makes sense what you are saying with regards to mother and offspring. I was simply trying to enforce the fact signs of evolution can occur quickly. It should be noted (simply by looking at dog variation) that vast morphological changes can occur over very few generations and not many mutations.

You are also correct with hox genes. Mutations within them will cause huge anomolies, but the fact that hox genes do exist shows the effectiveness of random mutations creating beneifits towards an environmental change.

100 years from now, given continued artificial breeding, does anyone think a separate distinct species of dog will be identified. I already think there are, such as the chihuahua and British mastiff.

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Originally posted by Krypton 100 years from now, given continued artificial breeding, does anyone think a separate distinct species of dog will be identified. I already think there are, such as the chihuahua and British mastiff.

Some of that is relative to the person defining the breed. A lot of the domestication of the dog took place thousands of years before history even began to be recorded. A lot of the breeds evolved back then from selective breeding and no one really payed attention outside of the regions where these animals were bred.

These days, things like the American Kennel Club and other international dog organizations are for more likely to define if a dog becomes a different breed

Remember also dog breeds are not different species. There is nothing genetically stopping a wolf and a chihuahua from breeding... Physically though...