What prevents evolution?

[Rduke55]

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The mutual infertility of the individuals within group B increases according to the same genetic drift that underlies the development of mutually fertile group A into (prospectively) mutually fertile group B.

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Before I agree with this, what do you mean by genetic drift?

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The usual random mutation referred to in this context.

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I just dont think random genetic drift would be sufficient to explain the amount of speciation in the time scale we have. I could be wrong though. Rduke? I think if we just allow for a random, Brownian-type walking motion through all the possible configurations, its going to take forever for group A and group B to drift far enough apart to be different species. I mean, it will definitely happen, and probably millions of times in the time span. But not nearly often enough.

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Drift can be HUGE in speciation. Depending on population size.

[Skidoo]

Selection, like something else I won't mention, happens.

It's the notion of speciation that's got issues with logic.

[Rduke55]

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Selection, like something else I won't mention, happens.

It's the notion of speciation that's got issues with logic.

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But you said populations could become mutually infertile with each other.
That's what speciation is. How's that' illogical?

And what's the something you won't mention?

[Skidoo]

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The mutual infertility of the individuals within group B increases according to the same genetic drift that underlies the development of mutually fertile group A into (prospectively) mutually fertile group B.

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Infertility with respect to whom?

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Each other.

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Each other at the individual level?

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Yes.

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Are you being vague on purpose?

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No.

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Then who do they mate with?

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That's just my point.

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How many generations would you say this infertility takes to get to?

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About the same number of generations separating the mutual fertility of group A and group B.

[vhawk01]

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Selection, like something else I won't mention, happens.

It's the notion of speciation that's got issues with logic.

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But you said populations could become mutually infertile with each other.
(That's what speciation is)

And what's the something you won't mention?

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Actually, I totally agree with him. Speciation really is a logically meaningless distinction. I mean, unless 'species' only means EXACTLY cannot mate with any other species. But even thats iffy, they can mate, with varying success, some of the times.

Calling two different things different species is a (nearly completely) arbitrary distinction. If that was Skidoo's point (I doubt it was) then I agree completely.

[Rduke55]

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The mutual infertility of the individuals within group B increases according to the same genetic drift that underlies the development of mutually fertile group A into (prospectively) mutually fertile group B.

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Infertility with respect to whom?

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Each other.

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Each other at the individual level?

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Yes.

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Are you being vague on purpose?

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No.

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Then who do they mate with?

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That's just my point.

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How many generations would you say this infertility takes to get to?

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About the same number of generations separating the mutual fertility of group A and group B.

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So you have a group of individuals where none of them can mate with each other?

And in the 2nd response, where do you get that idea from?

[Magic_Man]

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The mutual infertility of the individuals within group B increases according to the same genetic drift that underlies the development of mutually fertile group A into (prospectively) mutually fertile group B.

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Infertility with respect to whom?

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Each other.

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Each other at the individual level?

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Yes.

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Are you being vague on purpose?

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No.

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Then who do they mate with?


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I tried to have a very similar conversation with my biology major frind a while back; I don't understand speciation very well at all, and I'd love for someone to explain where I've gone wrong here (I'm sure I have). What I got out of it was this:

1) Mutations occur that make it harder for individuals with those mutations to mate with the non-mutated group. They are still successful sometimes, but their success rate is lower than non-mutated/non-mutated mating. Mutated/mutated mating is also more successful than mutated/non-mutated.

2) Mutated/mutated pairs happen more often, and the mutations get passed along. More mutations occur that make their offspring (probably several generations down the line) completely incompatible with the original group.

3) Now we have a situation where A can mate with B (but not very successfully), B can mate with C, but A cannot mate with C. If B dies out/mutates some more, then A and C are distinctly different species.

That's one mechanism by which it might happen. Just for the record, I'm told there is a "species" of bird that has this particular pattern; the ones on the west coast of the US can mate with those that live near mid-country, and the mid-country birds can mate with the east-coast birds, but west-coast can't mate with east-coast. Weird.

~MagicMan

[Rduke55]

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Selection, like something else I won't mention, happens.

It's the notion of speciation that's got issues with logic.

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But you said populations could become mutually infertile with each other.
(That's what speciation is)

And what's the something you won't mention?

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Actually, I totally agree with him. Speciation really is a logically meaningless distinction. I mean, unless 'species' only means EXACTLY cannot mate with any other species. But even thats iffy, they can mate, with varying success, some of the times.

Calling two different things different species is a (nearly completely) arbitrary distinction. If that was Skidoo's point (I doubt it was) then I agree completely.

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That's what species are - reproductively isolated populations. they can interbreed with each thter and are infertile with other species.

[Skidoo]

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Selection, like something else I won't mention, happens.

It's the notion of speciation that's got issues with logic.

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But you said populations could become mutually infertile with each other.
(That's what speciation is)

And what's the something you won't mention?

[/ QUOTE ]

Actually, I totally agree with him. Speciation really is a logically meaningless distinction. I mean, unless 'species' only means EXACTLY cannot mate with any other species. But even thats iffy, they can mate, with varying success, some of the times.

Calling two different things different species is a (nearly completely) arbitrary distinction. If that was Skidoo's point (I doubt it was) then I agree completely.

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A larger point is that speciation, defined as the production of a new group with which the original is not fertile, is essential to the supposed process of evolution.

[Rduke55]

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Selection, like something else I won't mention, happens.

It's the notion of speciation that's got issues with logic.

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But you said populations could become mutually infertile with each other.
(That's what speciation is)

And what's the something you won't mention?

[/ QUOTE ]

Actually, I totally agree with him. Speciation really is a logically meaningless distinction. I mean, unless 'species' only means EXACTLY cannot mate with any other species. But even thats iffy, they can mate, with varying success, some of the times.

Calling two different things different species is a (nearly completely) arbitrary distinction. If that was Skidoo's point (I doubt it was) then I agree completely.

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A larger point is that speciation, defined as the production of a new group with which the original is not mutually fertile, is essential to the supposed process of evolution.

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but you've been preaching on the development of infertility the whole thread.