Speciies? you gotta be kidding.

[Rduke55]

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You seem to be making the case that if we took a litter of puppies and totally isolated them into two groups on remote islands we have now created two species because they WILL diverge, drift, etc.

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I must be being unclear because this is certainly not what I'm saying. In this case they are interfertile and genes can flow between them.

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Yet, in fact, nothing has changed, we still have 'a group of puppies from the same litter.' Grabbing two groups from a ring species ( which we are all temporally a member of) is an upscale version of that.

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And I'm saying that it's not. The key to my point is that at some point two populations are unable to interbreed and no intermediaries exist to allow gene flow from one group to another. At this point, and not before, they are different species. They now will have a new class of different independent evolutionary trajectories that do not overlap (while there certainly may be convergence, etc. since they have a lot of the same raw materials).

These points are the joints.

[Rduke55]

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These days, I am looking forward to a genetic classification for "species," a percentage of difference in the genome, which would not take into account such elastic properties as interbreeding.

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There isn't a good correlation between "percentage difference in the genome" and species. It has to do with interbreeding.

[luckyme]

[ QUOTE ]
[ QUOTE ]
You seem to be making the case that if we took a litter of puppies and totally isolated them into two groups on remote islands we have now created two species because they WILL diverge, drift, etc.

[/ QUOTE ]

I must be being unclear because this is certainly not what I'm saying. In this case they are interfertile and genes can flow between them.

[ QUOTE ]

Yet, in fact, nothing has changed, we still have 'a group of puppies from the same litter.' Grabbing two groups from a ring species ( which we are all temporally a member of) is an upscale version of that.

[/ QUOTE ]

And I'm saying that it's not. The key to my point is that at some point two populations are unable to interbreed and no intermediaries exist to allow gene flow from one group to another. At this point, and not before, they are different species. They now will have a new class of different independent evolutionary trajectories that do not overlap (while there certainly may be convergence, etc. since they have a lot of the same raw materials).

These points are the joints.

[/ QUOTE ]

I'll leave aside ring species, dogs and wolves, and the temporal flow of evolution that dawkins covered and try one under your version of 'joints'

I take a large litter of pups and split them into two different remote islands. I kill off all other dogs on the planet.
Have I created two species already?

I come back in 1M years and find both islands overrun with thousands of doggish animals. A few hundred on each island can still breed with a few hundred on the other island if we put them in a pen together.
How many species do we have now?
More importantly, whenever we arrived at 2 species, when was it and why is it an obvious joint, like rocks and raindrops?

luckyme

[Rduke55]

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I take a large litter of pups and split them into two different remote islands. I kill off all other dogs on the planet.
Have I created two species already?

[/ QUOTE ]

I'm not sure what I'm missing here from my earlier posts. No, they are not different species, they can interbreed.

[ QUOTE ]
I come back in 1M years and find both islands overrun with thousands of doggish animals. A few hundred on each island can still breed with a few hundred on the other island if we put them in a pen together.
How many species do we have now?

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I think we have examples of ring species...that are pretty close to being two totally different species. Although in actuality we would most likely classify them as different species. I'm not arguing that all things we call species fit the definition to a T - I'm arguing that there are such things as species under the definition, and that most of the animals on the planet can be classified as such. Because of the lack of intermediates, animals can be classified into distinct categories due to their reproductive isolation. The way they got here is a continuum, but at this point in time they are distinct.

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More importantly, whenever we arrived at 2 species, when was it and why is it an obvious joint, like rocks and raindrops?

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Realistically when there is no probable chance for exchange of genes between two populations we often call them different species. For the cut and dried version when there is no way the two species can interbreed and don't have intermediates (which prevents gene flow) then they are different species.

[Prodigy54321]

what's that phrase he uses?...

"________ of the discontinuous mind"

the ancestor's tale was really an amazing book

dawkins is never afraid to tell the reader just how sure or unsure he is about certain details..like lineages and timelines

I loved the grasshopper's tale...and the picture of bush, powell, and a "genuinely black man" (can't remember who it is exactly)..asking..if aliens were looking at them..how many different races would they see [img]/images/graemlins/tongue.gif[/img]

[luckyme]

[ QUOTE ]
I'm not arguing that all things we call species fit the definition to a T - I'm arguing that there are such things as species under the definition, and that most of the animals on the planet can be classified as such. Because of the lack of intermediates, animals can be classified into distinct categories due to their reproductive isolation. The way they got here is a continuum, but at this point in time they are distinct.

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If there were actual joints it wouldn't matter if the intermediates were current or extinct. That's why rings species and dogs/wolves and fossil sequences are so frustrating under the 'species' approach... it's not an actual joint it's an attempt to create a joint ( which does usually work, but only by luck of extinction).

I may be explaining it poorly, have you read Dawkins comments on 'the illusion of discontinuity'? I was surprised when I ran into it because I didn't expect a biologist to support the claim that 'species' is an arbitrary boundary like most human created categories, and even fuzzier-than-normal. I've been yelled at when I've raised it in the past.

luckyme

[luckyme]

[ QUOTE ]
what's that phrase he uses?...

"________ of the discontinuous mind"

the ancestor's tale was really an amazing book

dawkins is never afraid to tell the reader just how sure or unsure he is about certain details..like lineages and timelines

I loved the grasshopper's tale...and the picture of bush, powell, and a "genuinely black man" (can't remember who it is exactly)..asking..if aliens were looking at them..how many different races would they see [img]/images/graemlins/tongue.gif[/img]

[/ QUOTE ]

I just looked it up. Dawkins calls it "the delusion of discontinuity" and " the tyranny of the discontinuous mind" and has some neat non-biological examples of arbitrary boundaries that we run into everyday in the Salamanders Tale.
Bush's "You're either for us or against us" is not one of his, but a simplistic example of course.

luckyme

[oe39]

of course they don't really exist as simply as they are presented...

[Rduke55]

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If there were actual joints it wouldn't matter if the intermediates were current or extinct.

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Well it does. Sometimes things dying is just as useful for separating things as things growing. Probably a terrible analogy, but fingers are formed initially by cells dying in such a way that separates tissue and forms them.

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That's why rings species and dogs/wolves and fossil sequences are so frustrating under the 'species' approach... it's not an actual joint it's an attempt to create a joint ( which does usually work, but only by luck of extinction).

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One thing one of my old professors said was that sometimes biology sucks because there's always an exception. Considering the gradual nature of evolution there will always be some lineages in transition.

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I may be explaining it poorly, have you read Dawkins comments on 'the illusion of discontinuity'?

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I have and what I'm saying doesn't really relate here. Of course everything is related along a continuum. But what I'm saying is that for a given slice of time species, as distinct groups, exist.

I've (and others) been annoyed by certain aspects of this particular section of Dawkins' writing for this very reason. I start talking about different species in class and all of a sudden we have to spend 15 minutes on this because they don't realize we're talking about something that that doesn't relate to. (I'm not making this claim towards you)

[luckyme]

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One thing one of my old professors said was that sometimes biology sucks because there's always an exception. Considering the gradual nature of evolution there will always be some lineages in transition.

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Some? ( just teasing )

I don't think there is a problem with the 'current separated groups' version as a useful category. The main thrust of Dawkins is in the lineage study. It doesn't make much/any sense to refer to species since there's no obvious joints in a lineage and you could create species at virtually every single ancestor by just using a different starting point and going back until you lose breedability.

Carrying over the helpful, if blurry, species category in a 'slice of time' as you mentioned into lineage discussion seems careless or confusing and/or unhelpful or whatever ;-) It would seem useful to clarify that upfront and then move on. We can refer to 'race' in a helpful way at times, even while acknowledging that 'race' is a really blurry and broad boundary. ( Yet, as my swedes and pygmies as the only living groups illustrated, it would seem glaringly clear that race existed if that were the case).

luckyme