# 'Ring species' **URL:** \ **Category:** Factual Questions\ **Created:** [February 23, 2007, 9:32pm UTC](https://boards.straightdope.com/t/ring-species/393436 "2007-02-23T21:32:24Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 25, 2007, 8:01pm UTC](https://boards.straightdope.com/t/ring-species/393436/21 "2007-02-25T20:01:36Z")
Right. Humans aren’t a “ring species”, we’re a just plain old ordinary “species”. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [February 25, 2007, 8:28pm UTC](https://boards.straightdope.com/t/ring-species/393436/22 "2007-02-25T20:28:15Z")
[QUOTE=chorpler] Then I don’t understand why you said “Yes. Yes, there is.” That’s about as far from what **Chronos** was asking as you can get. [/QUOTE] No, that’s exactly the situation that **Chronos** suggested. He proposed that the most distant populations (A and Z) at the farthest ends of the species’ range would be able to interbreed if they came into contact. That is the situation found in humans, as rather obliquely suggested by **Sage Rat.** The main difference is that human populations don’t form a “ring.” The initial major contacts between the most distantly isolated populations began with the European voyages of the late 1400s. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [February 25, 2007, 8:32pm UTC](https://boards.straightdope.com/t/ring-species/393436/23 "2007-02-25T20:32:59Z")
[QUOTE=Colibri] No, that’s exactly the situation that **Chronos** suggested. He proposed that the most distant populations (A and Z) at the farthest ends of the species’ range would be able to interbreed if they came into contact. That is the situation found in humans, as rather obliquely suggested by **Sage Rat.** The main difference is that human populations don’t form a “ring.” The initial major contacts between the most distantly isolated populations began with the European voyages of the late 1400s. [/QUOTE] No. He was talking about a ring where there are intermediate species that can breed with each other but _not_ breed with the endpoints (A and Z). There aren’t any human “intermediate species” that can’t interbreed with A and Z. Admittedly the way he phrased it might not make it clear, since he didn’t specify the part about “… and species more than a few letters apart can’t interbreed directly,” but that’s pretty much understood when you’re discussing “ring species,” at least in the common usage. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [February 25, 2007, 9:19pm UTC](https://boards.straightdope.com/t/ring-species/393436/24 "2007-02-25T21:19:45Z")
[QUOTE=chorpler] No. He was talking about a ring where there are intermediate species that can breed with each other but _not_ breed with the endpoints (A and Z). There aren’t any human “intermediate species” that can’t interbreed with A and Z. [/quote] Nope. Read his post: [QUOTE=Chronos] Are there any examples (outside of fiction) of “ring” species which actually form a complete ring, and not just a chain? So not only can A breed with B, and B with C, … and Y with Z, but Z can also breed with A? [/QUOTE] Where does he say or imply that any of the intermediate populations can’t breed with the endpoints? > [@](#): > > Admittedly the way he phrased it might not make it clear, since he didn’t specify the part about “… and species more than a few letters apart can’t interbreed directly,” but that’s pretty much understood when you’re discussing “ring species,” at least in the common usage. Not only didn’t he say that, that’s not what is “commonly understood” regarding ring species. The only requirement for a ring species is that the terminal subspecies not be able to interbreed; it says nothing about the situation between intermediate subspecies either way beyond the fact that adjacent ones can interbreed. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [February 25, 2007, 9:55pm UTC](https://boards.straightdope.com/t/ring-species/393436/25 "2007-02-25T21:55:17Z")
[QUOTE=Colibri] Nope. Read his post: Where does he say or imply that any of the intermediate populations can’t breed with the endpoints? [/quote] I think it’s clear that that’s what he was taking that to be an implicit part of the question, or else we wouldn’t even be talking about “ring species,” we’d just be talking about a regular ordinary species like humanity, where everybody can interbreed. For something to be relevant to a discussion of a ring species, there has to be a point where the subgroups can’t interbreed anymore. > [@](#): > > Not only didn’t he say that, that’s not what is “commonly understood” regarding ring species. The only requirement for a ring species is that the terminal subspecies not be able to interbreed; it says nothing about the situation between intermediate subspecies either way beyond the fact that adjacent ones can interbreed. Yeah, I tried to edit my post to change “more than a few letters apart” to “endpoints,” but it was too late. In any case, it’s clear that’s what he meant, and he has now verified that – the “terminal subspecies” in his question would be A and Z vs. M and N. Otherwise the question just makes no sense. Let me clarify **Chronos** ’s question using his terminology: Are there any ring species that form a true ring, where A can interbreed with B, B can interbreed with C, … L can interbreed with M, M can interbreed with N (but L and M can’t interbreed with A and B) … X can interbreed with Y, Y can interbreed with Z, and hey, Z can interbreed with A. Thus forming an actual “ring” instead of a “chain.” ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [February 25, 2007, 10:21pm UTC](https://boards.straightdope.com/t/ring-species/393436/26 "2007-02-25T22:21:25Z")
[QUOTE=chorpler] I think it’s clear that that’s what he was taking that to be an implicit part of the question, or else we wouldn’t even be talking about “ring species,” we’d just be talking about a regular ordinary species like humanity, where everybody can interbreed. For something to be relevant to a discussion of a ring species, there has to be a point where the subgroups can’t interbreed anymore. [/quote] Sure, but that’s not part of the _definition_ of a ring species. If you think differently, please provide a cite. > [@](#): > > Are there any ring species that form a true ring, where A can interbreed with B, B can interbreed with C, … L can interbreed with M, M can interbreed with N (but L and M can’t interbreed with A and B) … X can interbreed with Y, Y can interbreed with Z, and hey, Z can interbreed with A. Thus forming an actual “ring” instead of a “chain.” This is the situation that **Mangetout** described as a hypothetical, and as I have already pointed out it doesn’t fit the definition of ring species. Again, if you think differently, please provide a cite to the scientific literature. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 25, 2007, 10:34pm UTC](https://boards.straightdope.com/t/ring-species/393436/27 "2007-02-25T22:34:15Z")
In case there’s any lingering ambiguity, I did indeed intend to imply that each sub-population would not be interfertile with populations a few letters away. And while I recognize that such a situation is not the standard ring species, it does seem to encompass the concept: If one didn’t know of the existance of populations, say, N through Z, then populations A through N could constitute a traditional ring (or likewise for any other way of breaking up the populations). ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 25, 2007, 11:08pm UTC](https://boards.straightdope.com/t/ring-species/393436/28 "2007-02-25T23:08:05Z")
Regardless of what, if anything, it would be called; the hypothetical scenario I described above could only really occur by radiative diversification from a single point; for a true ring species to rejoin at the ends, it would require the restoration of compatibility, which is quite unlikely for organisms that have already diverged significantly. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [February 25, 2007, 11:19pm UTC](https://boards.straightdope.com/t/ring-species/393436/29 "2007-02-25T23:19:49Z")
To explicate a little further on this, it has often been assumed that populations of a species that are farther apart will be less likely to interbreed. This is in most cases imposssible to test under natural conditions, since populations that are far away are necessarily not in contact. It is only testable in the very rare case that a species has expanded until it entirely surrounds some geographical barrier and populations from distant parts ends of the range come into contact. The species does not necessarily have to form an actual ring. As it turns out, most supposed cases of ring species have not been confirmed. Gene flow does in general prevent the acquistion of isolating mechanisms. It is isolation over time, rather than distance, that tends to cause speciation. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [February 25, 2007, 11:35pm UTC](https://boards.straightdope.com/t/ring-species/393436/30 "2007-02-25T23:35:13Z")
[QUOTE=Colibri] Sure, but that’s not part of the _definition_ of a ring species. If you think differently, please provide a cite. This is the situation that **Mangetout** described as a hypothetical, and as I have already pointed out it doesn’t fit the definition of ring species. Again, if you think differently, please provide a cite to the scientific literature. [/QUOTE] I was just clarifying what **Chronos** meant, not challenging your understanding of the technical definition of “ring species.” [Previous page](https://boards.straightdope.com/t/ring-species/393436.md?page=1)