Talk:Species

The definition I learned in high school (I know, I've set myself up to be wrong already) was: two animals are the same species iff they can produce fertile offspring. Was that wrong/has it changed?--BlackGriffen

(1) That definition can only apply to sexually reproducing species (how do you determine whether or not two bacteria, each of which can reproduce alone by splitting, can "interbreed"?) (2) Even among higher species, the lines aren't that sharp. There are severals "sets" of species, such as arctic seabirds, where species A can and does interbreed with B, and B with C, and C with D...but A cannot interbreed with D. So where do you draw that line? --LDC

Another problem with the definition is that there are well-accepted 'species' that can produce fertile offspring, but generally do not in nature. For instance grizzlies and polar bears breed successfully in zoos. Conversely there are animals which we accept as the same species even though they obviously cannot interbreed. For instance no matter how much a Great Dane and Pekinese may want otherwise, physical mechanics will be a problem. Yet both are dogs. --BJT

The last example brings to mind the great song by Australian folk singer Eric Bogle; it is the tragic tale of "little Gomez" a chihuahua of great might and courage. He became enamoured of a lady St. Bernard. When our hero tried to consumate his love, she sat down and tragically terminated his efforts. :-) Eclecticology

I think it would clarify things to introduce a section outlining the three common ways in which "species" is used today. Perhaps something like:

• Taxanomic. Species are classified, more or less arbitrarily, according to readily observable features, such as number of teeth, leaf shape, colour of feathers, and so on. This is the most common usage in everyday life, is convenient for the production of field guides, but often sheds little light on the underlying genetic isues and can be quite misleading.
• Biological. A species is distinct from another species if the union of the two cannot produce viable offspring. Has a satisfying logic on first inspection and is very useful for practical work with plant and animal breeding, but riddled with inconsistencies [as pointed out by LDC & BJT above]: many particular seperate taxanomic species can interbreed freely but seldom do in the wild, and the ability of any two seperate species to interbreed can be highly variable: some horse-donkey unions, for example, produce healthy, fertile mules. An arbitrary dividing line must sometimes be drawn to define a particular species.
• Evolutionary. Species is defined by relatedness of DNA sequences. More closely represents the web of relationships between different lifeforms, but this deeper level of abstraction moves the whole concept of species a long way away from its commonsense meaning.

Each of these three ways of defining a species is useful, each has its weaknesses, and the continuing use of all three helps highlight the underlying fact that the natural world consists of humps and subtle gradients which the straight lines and boxes of categorisation schemes can only render imperfectly.

Errr .... that last bit is a bit flowery, but you get the idea. I'm reluctant to go chopping up an article that is coherent and reads well as it stands, but at present one must read between the lines to understand that 'species' is as variable and as slippery a concept as it is. Putting some of the more common current definitions into dot point form would help, I think. Tannin

These are definitely contrasts that should be made. And please don't worry about chopping up the article. I think the article needs massive reconstruction anyway. Most of the history of taxonomy stuff probably belongs in another article, as does the not insignificant summary of how evolution is supposed to work. --Ryguasu 20:58 Jan 31, 2003 (UTC)

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I'm removing the following bit of metaphysics:

It is unclear whether the category "species" exists "out there in the world", or if its existence is entirely dependent on our human classification systems. Answers to this question may hinge on one's understanding of epistemology as much as of biology.

While this is a valid point, it has nothing to do with species in particular. You can ask the same questions about just about any scientific concept, if not just about every concept whatsoever. The only reason this should stay is if it ties in to a larger argument or controversy about species. --Ryguasu 20:58 Jan 31, 2003 (UTC)

Yes, and I didn't like the phrasing. But there is another similar but I think more important point: prior to Darwin many naturalists did believe that "species" were real things; Darwin's major accomplishment was to redefine them as statistical phenomena. This accomplishment is bound to Darwin's rejection of intentionality, and these two elements of his thinking are where the conflict between his followers and "creationism" is crystal clear. I believe the article makes this clear, but I guess whoever wrote this short paragraph was unsatisfied. Perhaps there is a point here that really should be stated more emphatically? Slrubenstein

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Copied from discussion on talk pages between Alan Peakall and Slrubenstein

Hello SLR, If you feel like a change from talk on Israel/Palestine, I would value your thoughts on the coverage in Wikipedia of the word subspecies. A search shows that it is widely used in articles relating to particular animals, but a search on the article species shows no attempt being made to define it there. To ask a specific question, is it, in your view, correct to say that the majority scientific opinion captured in race, that human races have no objective existence, is equivalent to a statement that the species homo sapiens has no subspecies? -- Alan Peakall 13:10 Feb 18, 2003 (UTC)

Hi. I don't know enough about how zoologists or botanists uses the term "subspecies" -- is it the same as "variety?" Is a "subspecies" of a particular animal the same as a "population?" Offhand I would guess that what physical anthropologists call "populations" of humans may correspond to what zooligists call "subspecies" of an animal. I think the real problem is not the gulf between scientists who study humans and scientists who study other animals, but the gulf between scientists and laypeople. Scientists see "species" (and necessarily "subspecies") as statistical phenomena whereas many laypeople see species (and race) as fixed things. Slrubenstein

I am not confident of my understanding of the status of the word subspecies in technical discussion either, but as the parent article points to race, I believe that it should at least discuss the concept. It seems to me that there are these possibilities: 1) the concept of subspecies is in general no more useful than race is for homo sapiens and therefore is deprecated in technical discourse, 2) the concept of subspecies is meaningful for some species, but, at least since the extinction of homo neanderthalensis, not for homo sapiens, 3) the possibility that you suggest, 4) that those who defend the use of the word race in a biological sense mean something different from a technically accepted meaning accorded to the word subspecies. -- Alan Peakall 18:53 Feb 19, 2003 (UTC)

One of my professors, who in part studies different species' perceptual systems, claims that what gets called a new species and what gets called a subspecies is often more historical accident than principled distinction. Perhaps this is similar to the unprincipled way in which certain scientific results end up being called "laws", others "theories", etc.. (I know many people insist these words have well-defined technical meanings, but whether or not people pay any attention to those meanings in deciding which label to use is another story.) --Ryguasu 20:51 Feb 19, 2003 (UTC)

Tidy up needed

This article has grown into a bit of a mess. It starts well with a discussion of the different possible definition of species, but there's a ragbag of stuff at the end. It needs a thorough sort out - I'll get to it when I have time, but...

seglea 16:33, 9 Dec 2003 (UTC)

Might I suggest it be added that the definition in the Endangered Species Act which includes sub-species and "and any distinct population segment of any species or vertebrate fish or wildlife which interbreeds when mature." This is misleading and renders the question highly political.

Comment in edit summary box

Added this comment from 172.192.160.124, which was included in an edit summary box: --Lexor|Talk 01:14, 16 May 2004 (UTC)

I have not edited, but note the ambiguity of "ancestor" in "A phylogenetic or evolutionary or Darwinian species is a group of organisms that shares a common ancestor [species? individual?]."

Aristotle's sense of the word species

Aristotle, in his Categoriae, uses "genus" and "species" in a nonbiological sense more closely related to the terms generic and specific. Perhaps mention of this would be appropriate, if only for its etymological ramifications: the meaning of the word "species" grew more specific as time went on. - Jrn 16:29, 11 Oct 2004 (UTC)

It's definitely worth mentioning Aristotle, he came up with the original (very interesting and totally wrong) species concept, and started the work that Linnaeus picked up and improved. He also noticed the difference between individuals and between species, deeming them accidental and essential, a concept that stuck until Darwin, which is an interesting historical note. I've begun adding this. --Joe D 19:35, 11 Oct 2004 (UTC)