Speciies? you gotta be kidding.

[Rduke55]

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It doesn't make much/any sense to refer to species

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We're really talking about different things and different questions, but where I disagree strongly with you is the usefulness and reality of species as a distinct category.
And here is where our argument lies. "Species" is an essential concept in evolutionary study.

Just to be clear, you agree that if we took a census of all the sexually reproducing multicelled organisms on the planet (species for other organisms is a whole other, ugly question) most of them could be classified into distinct, interbreeding groups that are infertile with other groups?

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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

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It's really, really not, because of their unique evolutionary history after divergence. "Helpful" is a huge understatement.

I think this reading of Dawkins often sets up somewhat of a a straw man for many people. People read that and are all like "Stupid biologists, they don't have a clue as to what they're doing. Species. Pshaw." when we agree with all that tracing back diffiulties, transition problems, etc.

[Metric]

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The evolution/species one is harder to see and causes major problems with non-experts ( and perhaps even some experts) yet it is obviously no different in type.

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But it is.

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No, it's not. You pick a definition that makes your job/analysis easy and natural. Someone else might pick another definition that makes his job/analysis easy and natural. The two definitions might agree in the vast majority of cases, and disagree in a few cases. But which one is the "one, true" definition for those cases where disagreement arises? It's exactly the Pluto problem -- the argument is settled by vote.

[Rduke55]

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The evolution/species one is harder to see and causes major problems with non-experts ( and perhaps even some experts) yet it is obviously no different in type.

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But it is.

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No, it's not. You pick a definition that makes your job/analysis easy and natural. Someone else might pick another definition that makes his job/analysis easy and natural. The two definitions might agree in the vast majority of cases, and disagree in a few cases. But which one is the "one, true" definition for those cases where disagreement arises? It's exactly the Pluto problem -- the argument is settled by vote.

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Well I hope we're not all making up definitions just to make our job easier in science. We're talking about how our definitions reflect reality. In this case, we can certainly classify most extant animal species into distinct groups based on our definition of species and the other ones nicely fit into our idea of transitional speciation.

Same question I asked luckyme:

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Just to be clear, you agree that if we took a census of all the sexually reproducing multicelled organisms on the planet (species for other organisms is a whole other, ugly question) most of them could be classified into distinct, interbreeding groups that are infertile with other groups?

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[luckyme]

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Just to be clear, you agree that if we took a census of all the sexually reproducing multicelled organisms on the planet (species for other organisms is a whole other, ugly question) most of them could be classified into distinct, interbreeding groups that are infertile with other groups?

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We could do that with "has more than 50% brown pigment" or "more than 6 legs". Not trivializing the usefulness of the interbreeding constraint, but it is arbitrary nonetheless. I'm not sure why that fact is bothersome. I'd be interested in your expansion on that reasoning.

luckyme

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Well I hope we're not all making up definitions just to make our job easier in science.

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Of course we do. A given system might be completely uncomprehensible when analyzed with one set of otherwise perfectly good concepts but completely obvious in terms of another set of concepts, with subtly different definitions. This is why, for example, there are a bunch of different formulations of classical mechanics in physics (though they are all equally "right") -- setting up new definitions in terms of which to analyze the same physical system can be of enormous value.

In physics, we have gotten so used to the idea that we just assign the new definitions a different word, or append another word to clear up the ambiguity. E.G. "Oh, you're talking about canonical momentum, not linear momentum." And it's often seen as a sign of progress to tease apart two subtly connected but distinct ideas that were assumed to be the same and given the same name before.

[Praxising]

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

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This is a common misconception because this topic is taught in very basic ways unless you are taking advanced courses. So, the basic explanation is: a species is a group that can only produce viable offspring with those of it's own kind. But, in real science, it just ain't so.

There are many populations with shared consistently heritable traits that have species designations but can interbreed and produce viable offspring. They just usually don't for a variety of reasons. Most species of deer, most gibbons, many many birds, fit this description. We didn't know this during the hundreds of years of refining Linnaeus system. Until genetics.

In future, species designation will be a function of percentage of difference in a population's genome from another population. Or, we will do away with the species concept altogether. Lucky Me is right, species blur. This does not mean speciation does not occur, it just means biology isn't black and white and the living planet doesn't have neat edges between states of being.

[Rduke55]

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This is a common misconception because this topic is taught in very basic ways unless you are taking advanced courses. So, the basic explanation is: a species is a group that can only produce viable offspring with those of it's own kind. But, in real science, it just ain't so.

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I think you're off here. How many evolutionary scientists don't favor Ernst Mayr's definition of species? This theory has been favored in every class I've taken on the subject - both basic and advanced.

Also, I'm assuming this wasn't your intent, but I find the "in real science" part condescending.

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Most species of deer, most gibbons, many many birds, fit this description.

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Seriously? Can you give citations?

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In future, species designation will be a function of percentage of difference in a population's genome from another population.

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Well, how do you account for polyploidy in interbreeding populations and how would you standardize this across the wild variation seen across organisms? Since species is an evolutionary distinction, how are the barriers preventing gene flow between groups less suitable here?

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Or, we will do away with the species concept altogether.

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Jesus, that would just wreck the whole field.

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it just means biology isn't black and white and the living planet doesn't have neat edges between states of being.

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Look, I'm not saying there aren't exceptions. There are always exceptions in biology. But to dismiss the idea of species because every single animal doesn't fit perfectly in one definition (and doesn't fit because they fit our theory of how they get to be different species) or because you can't draw definite boundaries during their divergence is ridiculous.

[Rduke55]

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Just to be clear, you agree that if we took a census of all the sexually reproducing multicelled organisms on the planet (species for other organisms is a whole other, ugly question) most of them could be classified into distinct, interbreeding groups that are infertile with other groups?

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We could do that with "has more than 50% brown pigment" or "more than 6 legs". Not trivializing the usefulness of the interbreeding constraint, but it is arbitrary nonetheless. I'm not sure why that fact is bothersome. I'd be interested in your expansion on that reasoning.

luckyme

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Because that's the simple distinction that can be made that has massive influences on evolution. The other examples don't. Once you put up that barrier to gene flow then each population travels a unique path.

[Taraz]

Would it help the debate at all to come to a compromise whereby the idea of species is useful and explanatory but the edges are blurry? In other words, it's hard to actually draw distinct lines at the borders of each species, but the concept describes a very real distinction between animals?

[Rduke55]

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Would it help the debate at all to come to a compromise whereby the idea of species is useful and explanatory but the edges are blurry? In other words, it's hard to actually draw distinct lines at the borders of each species, but the concept describes a very real distinction between animals?

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Probably the most reasonable thing anyone's (myself included) said in this thread [img]/images/graemlins/smile.gif[/img]

My vigorous defense here comes from the fact that the definition of species I am talking about isn't like, say, the planet one where there's a continuum of sizes and there are really arbitrary boundaries (I know I'm simplifying) but that the criteria we use to classify different species represents a real distinction that is essential to our understanding of evolution.