"Unless I'm unclear on the idea, "species" are an entirely human construct. The end of one species and the beginning of another are like the lines on a map. We made them up out of convenience." -- rooter, in a comment on that page.
Interesting quote, but not completely accurate. Organisms are considered to be of the same species if they can (in nature) reproduce with viable, reproductive offspring. Thus we don't classify horses and donkeys as the same species because they (almost always) generate infertile offspring. Also, lions and tigers, which can produce fertile offspring, are separate species because they will never encounter each other in nature.
One problem in thinking that has to be overcome is that speciation does not follow a transitive property. In math, we say that "equality" is transitive since A=B and B=C implies A=C. However, in speciation, this property does not hold. A can be the same species as B, and B the same species as C, but A and C can be separate species. This problem doesn't really occur between species living at the same time -- generally a group that stays together evolves together, so you don't see such intermediates between two concurrent species. However, during evolution, there are such transitory subspecies. The comment you quote applies here in the sense that we may assign a species name to the transitory subspecies that reflects the parent species, or the later species, and this choice of naming is arbitrary.
the context of the quote is how the creationists are claiming darwin has been "proved" wrong because scientists following "darwinian" methods have failed to create a new species of anything (mostly experimenting with bacteria).
asexual repducing species don't fit into your description.
so the question comes, when does a single-celled organism split into two, where at least one of the two is not the "same" as its "parent". So far, science hasn't managed to get that to happen. They've certainly created breeds of things, as complex and "different" as the varieties of dogs and horses. But their realization is that the darwinian process, even through artificial stimulation, is still *slow*; 100 years isn't enough time.
The creationists (or their new scientific-sounding pseudoscience name, "Intelligent Design" proponents) claim that's proof that only a creator can actually make species.
But the Darwin supports just know that it means that things take a REALLY long time to change in biology, and that the kinds of varieties of bacteria, dogs, horses, humans, all in the same species, simply show the strong adaptability of those species.
for sexual reproduction, it does beg the question of why two very-close species don't reproduce together, particularly among birds and insects where the distinctions are so close as to just be a single stripe, or a longer tail feather, or whatever. Genetics says that likes lions/tigers they *can* reproduce with fertile offspring, but they don't. so why not?
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timeasmymeasure
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Date: 2004-03-29 09:23 pm (UTC)One problem in thinking that has to be overcome is that speciation does not follow a transitive property. In math, we say that "equality" is transitive since A=B and B=C implies A=C. However, in speciation, this property does not hold. A can be the same species as B, and B the same species as C, but A and C can be separate species. This problem doesn't really occur between species living at the same time -- generally a group that stays together evolves together, so you don't see such intermediates between two concurrent species. However, during evolution, there are such transitory subspecies. The comment you quote applies here in the sense that we may assign a species name to the transitory subspecies that reflects the parent species, or the later species, and this choice of naming is arbitrary.
for sexual reproduction, yes...
Date: 2004-03-30 05:31 am (UTC)asexual repducing species don't fit into your description.
so the question comes, when does a single-celled organism split into two, where at least one of the two is not the "same" as its "parent". So far, science hasn't managed to get that to happen. They've certainly created breeds of things, as complex and "different" as the varieties of dogs and horses. But their realization is that the darwinian process, even through artificial stimulation, is still *slow*; 100 years isn't enough time.
The creationists (or their new scientific-sounding pseudoscience name, "Intelligent Design" proponents) claim that's proof that only a creator can actually make species.
But the Darwin supports just know that it means that things take a REALLY long time to change in biology, and that the kinds of varieties of bacteria, dogs, horses, humans, all in the same species, simply show the strong adaptability of those species.
for sexual reproduction, it does beg the question of why two very-close species don't reproduce together, particularly among birds and insects where the distinctions are so close as to just be a single stripe, or a longer tail feather, or whatever. Genetics says that likes lions/tigers they *can* reproduce with fertile offspring, but they don't. so why not?