[Magic_Man]

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Magic_Man,
I don't like the "mutated" vs. "not-mutated" disctinction. I think it's quite a bit harder to understand speciation if you think of it in this context.

Think of a group that is comprised of individuals who are mutually fertile with one another. A very high percentage of this population can successfully mate with another individual of the opposite sex within this population. Not EVERY individual can, which I think is an important note.

Some event occurs which splits this population in two. Say it's a physical barrier... It doesn't necessarily *have* to be physical, but it must be something that prevents gene flow. Now, population 1 continues to change over time due to mutation/selection. Population 2 does as well. But, because they are not exchanging genes, they are no longer "co-evolving" sexually (to use the term loosely). The longer they remain out of contact (in terms of number of generations) the less likely it is that the future generations can mate successfully with the opposite population. There is no selection for fertility BETWEEN the populations -- thus the random mutations introduced will tend to cause them to diverge. At some point, it becomes very difficult for members of population A to mate with population B. Then, voila, we have two new species in terms of the classical definition. Over time, because they do not experience gene flow, there will tend to be massive differences in morphology which is why species tend to "look" so different.

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Matt:

A simple working definition is called for. If two individuals are potentially fertile with each other, they are of the same species. If not, they aren't.

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How does this apply in the A-->B-->C case? By your definition, A & B are the same species, and B & C are the same species, AND YET! A & C aren't the same species? This happens in the real world. Defining a "species" is a tricky pancake.

~MagicMan

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That's good because I like pancakes, with coffee in a roadside dinner after hiking down the mountainside rocky white with snow.

There is no A-->B-->C case, or even a truly A-->B case. That's the whole point.

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You've managed to talk in a full circle now. Are you seriously saying that a dog and a cat aren't different species? Or simply that they 'always were'? I figured this was the typical micro/macro evolution fallacy, but you did a good job of veiling it until now.

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No veils necessary. Evolution, as defined above, has issues with logic. That's what's been presented.

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Even if speciation had issues with logic, (it doesn't - many of the issues here are semantic or other problems of definition), that doesn't mean that evolution has problems. Evolution does not require speciation.

~MagicMan