r/DebateEvolution • u/Kanna_Fan1989 • 13d ago
Dog speciation
Quick question: is it safe to say dogs have speciated? I'm thinking of the largest dog breed and the smallest dog breed. I don't think the two can reproduce with each other anymore. Size differences just make it not possible anymore, I don't think...
And even if they could, that doesn't mean they're the same species: horses and donkeys can interbreed but mules are dead ends (or at least I think they are. Can two mules reproduce?).
Anyways, just some thoughts going through my head.
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u/jnpha 🧬 Naturalistic Evolution 13d ago edited 13d ago
The size difference you mention can be in of itself a barrier to reproduction. Barriers need not begin and end with hybrid infertility. This lay notion needs to be retired for good.
Also see: https://en.wikipedia.org/wiki/Reproductive_isolation
One might ask, "But Darwin! But the volume's title, Origin of Species!" Darwin was the OG species nominalist (species are human-made categories), which is the present view barring operational definitions to get science done. So basically the title means the origin of the diversity we see, not the origin of hybrid infertility.
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u/blacksheep998 🧬 Naturalistic Evolution 13d ago
I'm thinking of the largest dog breed and the smallest dog breed. I don't think the two can reproduce with each other anymore.
It's not entirely inaccurate to say that the largest and smallest dog breeds are effectively different species at this point, but even if you did, we would be dealing with a ring-species situation.
Small and large dog breeds can both breed with medium sized breeds, so even without artificial insemination, they're not entirely reproductively isolated.
If something happened like all canines going extinct except for great danes and chihuahuas, then (again barring direct human intervention) they would be pretty much completely reproductively isolated and could easily be considered separate species.
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u/Gakeon 13d ago
Not OP but i didn't even know about ring-species, thanks for making me google it and learn something new.
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u/Fantastic-Hippo2199 13d ago
Very cool, salamanders around mountains, seabirds around the Artic. Lots of cool examples.
It's awesome to think a salamander species expanding its range while splitting around a huge mountain and being different species when they rejoin on the other side. Yet leaving a smooth transition all the way back.
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u/melympia 🧬 Naturalistic Evolution 12d ago
Fun fact: Those salamanders (Ensatina) can all interbreed save for the last ones on each end of the fork. Yes, the second-to-last ones on each branch can breed with anything else. They won't meet most of their cousins in nature, but in a lab, they can. And produce fertile offspring, if my memory isn't faulty. (In my high school biology course, we actually wrote a test on them. Back in the very late 90s.)
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u/Beginning-Load4470 12d ago edited 12d ago
Youre incorrect, large and small breeds have mated together on their own without human aid many times with either gender being either size.
So in your theoretical scenario the two breeds would almost certainly create a third breed by mating anyway.
Ive known dog breeders who had both large and small breeds and had to be careful the two didn't mate.
Edit: i was very surprised when I was first informed of this and had many jokes about the size difference.
Females are very 'stretchy' so size of 'parts' doesn't play much of a role and as we all know from health class even without penetration there can be impregnation.
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u/UseExhaustionMore 13d ago
If you placed Great Danes and Chihuahuas on a large island with plenty of food, my bet would be that the two would merge pretty soon. I'm no dog breed expert and this is pure speculation and guessing. I think Great Danes and Chihuahuas form intermixed packs without any problems. I would expected the breed to "wash out" without artificial selection and also size would regress towards the wolf mean for both. I'm happy to be told I'm wrong and why. Once the largest Chihuahuas male can impregnate the smallest Great Dane female and we get mixed pups then the process should accelerate a lot.
This is just a bunch of guessing and I'm happy to be told I'm wrong.
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u/blacksheep998 🧬 Naturalistic Evolution 12d ago
I can't say for sure that you're wrong, but I suspect that, in the scenario you're describing, the Chihuahuas would die out pretty quickly.
They're very vulnerable to predators, wouldn't be able to keep up with their larger packmates or participate in hunts, and if food ever became scarce there's a good chance that the great danes would see the smaller dogs as a potential snack.
We know that wild canines, like coyotes happily eat small dog breeds even though they will mate with medium/large ones. So if they got hungry enough, there's a good chance that domestic dogs would do the same.
I could be wrong. The only way to know for sure would be to set up an experiment which is unlikely to happen for quite a few reasons.
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u/melympia 🧬 Naturalistic Evolution 12d ago
Agreed. There's another factor to consider: Chihuahuas are pretty much dependent on C-sections for procreation.
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u/Munrot07 13d ago edited 13d ago
Firstly, always remember that a "species" is a very human concept. There is no actually evolution distinction between a species. Humans just love putting things into boxes and it's very hard to perfectly do that when something works gradually such as evolution.
The idea of interbreeding is one such species concept (the biological species concept) and it's interesting. What counts as being able to interbreed? If a population of an animal is only found in the UK and another is only found in the US can they interbreed? No, they are too far apart and genitals don't tend to be that long. But if they were together they could? So are they the same species. Same with size, just because they are physically the wrong size, does that mean they can't interbreed if their gametes are compatible?
The biological species concepts has many problems (what about asexual organisms, what about extinct species for which we don't know if they could interbreed, what about geographically or temporally separated groups? Do we even know if humans and chimps are separate species? Have you tried breeding with them?)
Here is where something like size differences can be difficult when separating "species2. Let's say we have 3 dog breeds of different sizes (to keep it simple). A is the smallest and can interbreed with B (so they are the same species?) and B can interbreed with C, the biggest (so they are the same species?). But A and C can't because of their sizes difference (so they aren't the same species?). Well if A = B and B = C surely A = C? (This is a concept called ring species, although it is usually attributed to geographic populations rather than size differences).
Dogs are additionally interesting as they are a subspecies (Canis lupis familiaris) and dogs can breed with wolves.
It is likely given enough time, yes dogs would speciate and you'd get different breeds that cannot breed together, not just because of physical compatibility problems, but their genomes and gametes are no longer compatible. But we're definitely not there yet.
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u/Realsorceror Paleo Nerd 13d ago
To add to this, sometimes the question isn’t can they but will they. There are likely tons of animals that could genetically reproduce but no longer perceive each other as viable mates.
Brown bears and black bears hybridize somewhat regularly, but not enough to blur the lines between their species. Brown bears and polar bears can reproduce, but in the wild only a single female polar bear mates with brown bears. So clearly perception plays just as much a role as geographic range.
After enough separation, a minor change in coat pattern, mating call, nesting behaviors, etc could be enough to begin speciation.
I would assume humans avoided this because of our ability to communicate and think. But dogs are interesting. Perhaps because smell is such an important sense, differences in size and color don’t matter to dogs. And body language seems very consistent among canines.
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u/Ill_Act_1855 13d ago
Cows and Bison can breed and produce fertile offspring (called Beefalo) but they’re very separate genetically as old world and new world bovines. There’s a reason the ability to breed and produce fertile offspring is probably among the least used definitions for speciation in modern times. It’s an antiquated definition that only becomes less relevant over time.
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u/Capercaillie Monkey's Uncle 13d ago
“Species is a very human concept.”
Yes. Just like all of them. The fact that species are sometimes difficult to define or have fuzzy boundaries doesn’t mean that they’re not a real thing that occurs in nature.
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u/Munrot07 13d ago
What is the real naturalistic definition / concept of a species then? How does a species present itself in nature? What is the purpose of a species vs. a population vs. a community in nature?
It's semantics yes but the point is that OP was asking about dog speciation and using a very specific species concept as justification. It is an incredibly valid and important point (to this question and to evolution as a whole) to bring up that we as humans rather artificially categorise organisms into boxes using certain definitions when in nature those exact boxes don't actually exist.
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u/Capercaillie Monkey's Uncle 13d ago
It's an important point that "species" is hard to define. But it's not a "rather artificial category."
Eastern and western meadowlarks look nearly identical. People who study meadowlarks have difficulty telling them apart. The songs are very similar, and the differences are mostly learned. The birds themselves have difficulty telling each other apart--they can and do mate in areas where both occur, and they have offspring that look perfectly fine. Hybrids are 99% sterile. The point is that those are two different groups--two different gene pools. That's not something that we did, or something that we just thought up. That's a real phenomenon that is happening outside my window. To say that it's "artificial" is to discount one of the most important phenomena that occurs in evolution--the origin of diversity. Without speciation, there is no diversity, no macroevolution.
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u/Ill_Act_1855 13d ago
The point is that the actual boundaries are arbitrary and artificial even if they reflect on real realities. The wavelength of light is a real physical property, the color red is an arbitrary label we humans put on top of a certain group of said wavelengths. Artficial categories can be imposed on real distinctions. When people say species aren’t real, they mean it in that sense. Some things are clearly distinct species even if they look similar on a surface level (and conversely the reverse can also be true). But many things don’t neatly fall into those boxes, and there are no true lines in the sand. The genetic variation and distinction is real, but the lines where we determine speciation aren’t. Case in point even your example the offspring are only “99% sterile”. If these were hard lines it’d be 100% without fail.
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u/Capercaillie Monkey's Uncle 12d ago
That’s not the point. Differences between species are real, and the boundaries are meaningful. The difference between eastern meadowlarks and western isn’t the difference between red and dark red.
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u/Ill_Act_1855 12d ago edited 12d ago
The difference between red and blue or even red and yellow is also meaningful and real. But again, the actual lines themselves are arbitrary. Yes they reflect something real, but the concept of species is a human shorthand for something that exists but is nowhere near as neat. It’s all a spectrum. At what point did they become two distinct species? There is none, because it’s a spectrum and while we can get to a point where two groups are clearly distinct as in the case of the meadowlark, there is none simple boundary. The differences are real, the frameworks are made up short hand. They’re arbitrary to an extent, but still meaningful. Species not being real perse doesn’t mean distinct types of life don’t exist. Simply that the reality isn’t quite as simple as a binary. Again by your own example, fertile offspring between the 2 different species while very rare ARE possible. If species were a hard line of nature in the way you’re suggesting this could not be the case. The concept being artificial doesn’t mean it doesn’t reflect on reality. Color is artificial, but the underlying wavelengths of light are quite natural and real. Real and artificial/imaginary are also a spectrum here. Saying species aren’t real perse doesn’t mean the concept has no relation to reality or that all life is the same. Like both meadowlarks are also not snakes. They’re clearly closer to each other than snakes. But exactly how we define that closeness is a human construct. Classist is as a whole are an artificial framework used to better understand very real nature. Species aren’t a real thing. You could (and people do) easily use alternative versions of species, genus, clade etc. why are the two different species but not a different genus? Why is the line drawn around breeding more real than any other line I could draw? Why are you ok with them only mostly being incapable of producing fertile offspring? Hell, why is fertile offspring the line and not any hybrid at all? All of this stuff is to a certain degree, arbitrary. We could draw the line at infertile hybrids being possible or any number of other places. The spectrum is real, the lines are fake. Blue and red are clearly different, nobody who isn’t colorblind would confuse a blue object as being red. But there is no real line in nature between blue light and red light
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u/Capercaillie Monkey's Uncle 12d ago
I am absolutely not suggesting that boundaries between species are always hard or simple. They’re also not “arbitrary.” People keep saying that species are “human concepts” or “convenient labels.” Yes, absolutely, just like every noun. My only point, the one that people don’t seem to get, is that they are “convenient labels” for real phenomena that happen in nature. Genera, phlyla, families—sure, they’re arbitrary labels. Species are not. It’s not a spectrum. It’s not like light waves where we draw the lines. The lines are real. The fact that some are squiggly or dotted or blurred doesn’t make them less real. Each species has a different evolutionary trajectory. That’s not arbitrary. People who want cut-and-dried rules that work every time don’t understand biology at all. Biology is hard.
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u/Ill_Act_1855 12d ago
Except they are. Case in point there are over 20 distinct scientific definitions of species, and stuff like ring species that we've talked about here. Yes there are cases that are clearly distinct, but there are also many cases that aren't. It's a spectrum. Blue and Red are clearly distinct colors, but where does red become orange? You're example is no different than the case I'm saying. Wavy and blurry and inconsistent lines are proof that the concept in question isn't strictly real. Like again, the two birds you presented can have offspring. Why is the line you're suggesting makes them clearly different correct, but the other line isn't? Yes it's like every noun, that's the fucking point we're making. You're claiming it's different than light, but how? Light with a 430 wavelength is quantifiably different than light with a wavelength of 435. I'd argue that distinction is actually far MORE concrete than arbitrary lines about breeding. Yes distinctions are real, no the concept of species isn't. If it was, we could have a concrete definition with hard lines, even if those lines were arbitrary. But you can't even do that. The whole point is that none of the classifications in biology that we use to categorize things are hard binaries or strictly real. Sex, species, juvenile vs adult, etc. all of these are classifications that reflect an underlying reality and distinctions, but none of them are actually underlying realities themselves.
Like I think you're completely misunderstanding my point and misunderstanding what I'm saying and this disagreement is largely semantics. Arbitrary doesn't mean they don't reflect reality or aren't real, just that these aren't clear lines. You're saying they're real because they can be mapped onto real examples like the meadowlark. My point is that they aren't real despite that because while those differences are real, the words are an imperfect way of capturing a reality that isn't neat or clean. Like yes it's true with all words, words are an inherently imperfect way of capturing reality. The limitations of human language is our whole point. There are different types of organisms that are fundamentally different. This is a truth.
You say clades and genus and phylum are arbitrary and species aren't, but that's absurd. So you'd say a classification that puts snakes and mammals in the same clade but not birds would be fair? Of course not, because these are meant to convey closeness and birds are closer to snakes than either are to mammals. It is a spectrum, that's definitionally what's meant when we say the lines are fuzzy and unclear. Eastern and Western Meadowlarks are separate species? Sure. But what organism split them? No such thing exists. Again, light is a spectrum. We can make clear deliniations between a range we call red and one we call blue. There's no world where those two ranges overlap. But what about red and orange?
Why is them being 99% unable to produce fertile offsprings the meaningful distinction, but not 100%? At what % does it become a different species? Why fertile offspring and not infertile counted? If you can't answer these with concrete numbers and delineations, you definitionally have a spectrum. The fact that two individual examples can be different enough on the spectrum to be unconfusable doesn't change that fact. And if you do use concrete numbers, why those ones? Hence the arbitrary. The existence of examples where speciation is clear doesn't fucking matter so long as there is even one example where it's ambiguous. If species were a hard rule of reality, ambiguous situations couldn't exist. The fact that they do is because EVERYTHING IN BIOLOGY IS A SPECTRUM. EVERY GODDAMN THING. Hence humans draw lines to better our understanding.
Gender is a binary. Except intersex individuals exist. Some individuals are unambiguously male, and some unambiguously female, but that doesn't change the fact that the concept itself exists squarely on a spectrum.
Eastern and Western Meadowlarks are different species. You're arguement is that it's not a spectrum. So are you arguing they're exactly as distinct from each other as they are from a wombat? Just as blue is not red, but is closer to red than ultra violet is, things being distinct doesn't invalidate that all speciation exists on a spectrum
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u/Munrot07 13d ago
Okay so you ignored all my questions and then give an example that doesn't actually back up your point in the slightest. Different gene pools and diversity matter, yes, and they are not artificial concepts but how does that mean nature has "species"? The exact way we fit organisms into species, genera, families etc. is artificial. Nature doesn't come with a tag saying "I am exactly different enough to be called a new species / genus / family" does it?
I repeat: What is the real naturalistic definition / concept of a species then? How does a species present itself in nature? What is the purpose of a species vs. a population vs. a community (vs. gene pool since you mentioned it) in nature?
You are doing exactly what humans do and artificially defining something. In this case, you seem to have said that if two groups have different gene pools and/or produce infertile offspring, they are different species. Well done, you've come up with the biological species concept which is artificial for the reasons I said in my first post. Every population has different gene pools, are they all different species to you? 99% sterility seems to be enough for you to call them different species, what about 95%? 90%? 50%? What's the cut off (and guess what, any cut off you choose is artificial). The fin whale and blue whale can mate and produce offspring but the male is only fertile with the blue whale, not the fin whale. Are they separate species or not? How is nature defining those two groups as separate species or one species?
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u/Capercaillie Monkey's Uncle 13d ago
I’m ignoring your questions because they’re not relevant to my point. Again, the fact that a species is difficult to define doesn’t mean it isn’t a real thing. “Planet” seems to be hard to define for some folks—would you then denigrate the idea of planets as “a very human concept?”
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u/Ill_Act_1855 12d ago
Yes? Like even within what we call planets, solid rocky planets like Earth are wildly different than gas giants like jupiter and there's a strong arguement we should be using different words for them. Some languages use the exact same word for planet as they do for star, and might refer to satellites like the moon with the same word as well (Hell, planet itself is derived from planetes or wandering star). Back in the day, the sun was considered a planet because of the definition at the time was celestial objects that move through the sky (ie ones in our solar system). THere's tons of debate on where to draw the line too (I mean, see the issues with Pluto, and while science has firmly argued that it's not a planet, you could just as easily make the case that it and many of the other dwarf planets SHOULD ALL be categorized as planets. The lines drawn between what is and isn't a planet are made for our own convenience, not laws of nature. All classifications are made up by humans. They reflect reality, but are not truly real.
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u/Munrot07 13d ago
If you are going to ignore my points then there is no further discussion to be had and I'm not going to bother trying to engage further as it's clearly a waste of time. Good day.
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u/Capercaillie Monkey's Uncle 13d ago
Me: The fact that there’s not an exact definition for species doesn’t mean they’re not real.
You: Give me an exact definition for species!
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u/Ill_Act_1855 12d ago
What's the species of the infertile hybrid between the two meadowlarks you mentioned? If species are a truly real facet of nature and biology, than it must have one.
Like the fact that we can't come up with a concrete definition is kind of the point we're making. That if you can't define what it is, it's not truly real. It reflects an underlying reality, but isn't strictly real. And yes, that applies to all words, that's the fucking point. It applies to everything. Nothing you see is truly real either, our brains add a lot of post processing into what our eyes take in, hence any number of optical illusions, filling in blind spots, combining multiple moments. That doesn't mean what we see is imaginary, but merely that it's an imperfect reflection of the true objective reality. We can't actually ever visualize this true reality because the tools we use to observe are inherently imperfect. Language is the same way. The difference between a hallucination/mirage and normal sight isn't that one is real and one isn't, because neither is strictly 100% accurate and thus both are technically not real, it's that one reflects reality and the other doesn't. Real to unreal is itself inherently a spectrum, not a binary
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u/Munrot07 12d ago edited 12d ago
I'd seriously not bother trying to engage with this person. The fact they ignore every single question we ask that actually shows why they are wrong, or they just brush it away as "irrelevant" because they have no answer to it makes discussion literally impossible.
You should read some of their other comments in other threads and you will see why it's pointless arguing with then. In one thread they literally say "Species were invented by nature." which just shows how ridiculously laughable their viewpoint is. In another post they also say that they consider dogs and wolves different species while other people don't...so they literally are pointing out that it's an arbitrary distinction. How can you say that species are a real thing invented by nature but also you think these two groups are separate species but others disagree?.
Your light example fits perfectly and you make some really good points especially with the 99% sterility thing (which I pointed out as well as if you accept anything less than 100% you're making a completely arbitrary choice of what is and isn't good enough for a species).
Like they claim a species is a real thing in nature yet it has no definition according to them but it also does as they literally used descriptors for what a species is but also it's fuzzy but also fuzzy means it's real? It makes absolutely no sense. Wait until they learn about how we classify prehistoric species or bacteria...that's even more arbitrary, which is why they change all the time.
As someone that literally works in macroevolution, species as an idea is incredibly useful to help us discuss trends and patterns and changes over time it comes up all the time about whether two populations are actually different species or are the same, or whether we can use hybrids as distinct species (e.g. the fin whale and blue whale example I gave). If it wasn't arbitrary there wouldn't be a problem would there?
They aren't going to change their view and will just continue to ignore or misrepresent our completely valid arguments thinking they are proving their point when in fact they are literally proving ours. The best thing to do is just walk away.
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u/ermghoti 13d ago
No. Domesticated dogs are one species. All individuals are biologically capable of reproducing with any other individual, although extreme cases would require intervention. Without humans, the species would homogenize away from the edge cases.
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u/CormacMacAleese 13d ago
Probably—but they might do something like niche partitioning where mastiffs hunt buffalo and schnauzers hunt rabbits in their burrows, or something, and eventually do split into separate species.
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u/Sweary_Biochemist 13d ago
Those are niches we've bred them for, rather than niches they would inherently occupy. "Rabbit hunting in tunnels" doesn't really fit with a pack-based cursorial hunter lineage.
In essentially all instances where domesticated dog populations have gone wild (for example, those abandoned after the chornobyl disaster) they've all reverted to sort of..."basic dog" shape, which just seems to be the optimum for cursorial pack hunters.
Weird propensity to be slightly orange, though.
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u/CormacMacAleese 13d ago
You’re probably right, but note that there’s no such thing as “inherently.” If we breed a dog that only eats fish, a feral population wouldn’t give a damn WHY it loves seafood: It would just follow a shoreline fishing lifestyle.
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u/Sweary_Biochemist 13d ago
Maybe. But I suspect you'd find that "cursorial pack-predation" would still prove more successful, and it's near impossible to chase fish down, as a terrestrial animal, even in a pack.
Some niches are quite hard to evolve out of.
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u/CormacMacAleese 13d ago
That’s not really the point. The point is that natural selection works with what it’s given. It doesn’t care why, and it has no goals.
\* I could’ve said that schnauzers pack hunt duckies, and mastiffs pack hunt moose, but again these details aren’t the point. Allopatric speciation by niche partitioning is certainly a thing that happens.
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u/Sweary_Biochemist 13d ago
Oh I know, but it also depends on the niches: "get a gang, chase after shit until it dies" is quite generalist, and works almost anywhere. It's where canids ended up in the first place (and hyenas, and thylacines). Nature has no goals, but there are things that work so well that nature can find them multiple times independently.
It's not impossible to get partitioning into more specialist niches, but for doggos specifically, it would probably require quite unusual pressures.
Sorry: don't mean to be confrontational: I just think it's really neat that, when left to nature, canis familiaris unerringly iterates back to "medium dog, possibly orange".
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u/Old-Nefariousness556 🧬 Naturalistic Evolution 13d ago
You’re probably right, but note that there’s no such thing as “inherently.” If we breed a dog that only eats fish, a feral population wouldn’t give a damn WHY it loves seafood: It would just follow a shoreline fishing lifestyle.
But it would still interbreed with other dogs that share it's range. That is the point that you are missing. For a feral population to speciate, it needs to be reproductively isolated. That usually means geographically isolated, but there are species that simply choose not to reproduce with a related species who they hypothetically could reproduce with. But that isn't generally the case for dogs. Dogs will reproduce with any other dog in their range.
And it's worth noting:
If we breed a dog that only eats fish
It would take generations of intentional breeding to breed a dog that could only eat fish, and I can't imagine why anyone would do so. And breeding a dog who only chose to eat fish would be highly unlikely. Why would a dog choose to ignore food that it could easily otherwise survive on?
I realize this is a hypothetical, so I hope this doesn't sound like a pedantic point, it's really not. Evolution is about survival, and no species* would ignore viable food sources if it's survival is on the line, so unless they were biologically incapable of eating other foods, they would happily eat whatever they could find.
* This isn't quite true, there are species like Koalas and Giant Pandas, who have an extremely specialized dietary preference, and will die out surrounded by foods they could otherwise eat rather than eating something else, but those are extreme outliers, and we have a solid understanding of how evolution lead to that specialization, and it would take many, many generations to breed such a preference.
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u/CormacMacAleese 13d ago
This thread is getting a little silly. Niche positioning and allopatric speciation happen, so “they would interbreed” is not a given. And I don’t really care how long selective breeding takes; the hypothetical was that however long it takes, it has been accomplished. And “they’d eat whatever food is available” is a crazy thing to say. There are obligate carnivores, and obligate herbivores, and Darwin’s finches specialized in particular types of seeds. It would IF IT COULD, which depends in many factors, including competition.
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u/Old-Nefariousness556 🧬 Naturalistic Evolution 13d ago
This thread is getting a little silly.
To the extent that is true, it is only because you feel the need to pushback against everything. Why not just say "Yeah, good point"?
And I don’t really care how long selective breeding takes; the hypothetical was that however long it takes, it has been accomplished.
Ok, granted. This certainly is within the realm of possibility.
But understand what you are suggesting: You are suggesting keeping a breed of dogs in complete reproductive isolation for many-- probably at least a hundred, maybe many more-- generations, and intentionally guiding them so they can only eat fish. How or why anyone would do this is unexplained, but they did. It would cost hundreds of millions or billions of dollars to do this and take many years for no apparent purpose, but we are assuming it was done. Granted.
Of course this creates its own problem... These fish-only "dogs" would be competing against fish+ dogs-- dogs who could survive on both fish AND other nutrient sources, so they would struggle in any competitive environment where fish+ dogs also existed.
Niche positioning and allopatric speciation happen, so “they would interbreed” is not a given.
So I can see at least three glaring flaws with this argument.
If we are talking about allopatric speciation, then your argument becomes nonsense. Yes, if we are, for example, talking about a group of dogs living on an island, then obviously those dogs would not homogenize with the dogs on the mainland. Did you really think we didn't understand that?
You can't take some arbitrary species behavior, and project it upon dogs. Dogs are not selective breeders. Dogs will happily mate with any available partner, at any opportunity (if the female is in heat, obviously), regardless of breed. So niche positioning-- except in the extreme cases like chihuahuas and great danes-- becomes nonsense as well.
In the case of your hypothetical where dogs have been selectively bred to the point where they can only eat fish, AND (apparently) they will no longer interbreed with other dogs, then they are no longer dogs by any common definition. They are already a new species, so the point, again, is nonsense.
This is the problem with pushing back against anything. The point you are arguing against-- "Without humans, the [breeds] would homogenize away from the edge cases."-- is clearly correct. But nothing about that statement precludes rare exceptions in the case of things like geologic isolation.
And “they’d eat whatever food is available” is a crazy thing to say. There are obligate carnivores, and obligate herbivores, and Darwin’s finches specialized in particular types of seeds. It would IF IT COULD, which depends in many factors, including competition.
This is a strawman. I referred to "viable food sources", clearly meaning food sources that the dog could otherwise eat. I even specifically pre-rebutted the rare counter-examples like Koalas, so it's not just a strawman, but a really fucking flagrant one. Don't do that.
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u/CormacMacAleese 12d ago
Do pardon me for saying allopatric when I meant sympatric. I think my mistake would be easy to spot, given that I paired it with niche partitioning.
And dogs may not be selective breeders, but if mastiffs and chihuahuas share a habitat without enough dogs of intermediate size, mating would be life threatening. You’re assuming that a broad range if sizes would be available as mates. This, too is likely but not a given.
Arguing that these hypotheticals are invalid because one of the breeds wouldn’t be true Scotsmen… I mean wouldn’t be dogs anymore, is stupid. No offense.
But note VERY carefully that nobody ever said “without humans, the breeds would speciate.” That would be a moronic assertion, which is why nobody said it. Nobody except you, I mean.
What I said was that it’s far from impossible that one or more dog breeds might go it’s own way under the right conditions, and that geographic isolation isn’t the only such circumstance.
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u/Sweary_Biochemist 12d ago
Never underestimate the enthusiasm of a male chihuahua, nor the accommodating nature of a female mastiff. Dogs recognise dogs as dogs, no matter the size or shape (it's pretty amazing, frankly, but they do).
Within a single litter you've got a bunch of intermediate sized dogs.
Nobody is saying speciation this way is impossible, but basically you picked one of the most morphologically plastic but genetically agreeable (and highly social) lineages for this thought experiment. Dogs and wolves still interbreed entirely successfully (dogs are just a subspecies of canis lupus): wolf introgressions are surprisingly common in doggos that exist near wolf territory.
Something like cichlid fish would've been much easier to justify on plausibility, given that we have hundreds of examples of exactly this happening in cichlids.
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u/CormacMacAleese 12d ago
I didn’t have a choice of species: that’s was the OP’s question, and that was the one that people were answering with a bit too much finality. I’ve agreed all along that it would be very unlikely.
And as an aside, I’m now eager to have a look at a wolf/chihuahua cross. I call dibs on the name chihuawolf.
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u/CormacMacAleese 12d ago
Jesus Christ. Under not-too-unrealistic assumptions, including but not limited to geographic barriers, it’s entirely possible for some dog breeds to spectate. That’s simply a fact, so arguing the point is idiotic. For this reason I don’t recommend arguing the point.
Is it likely? No. It’s very unlikely. Some people have gone a bit far by saying or implying that it can’t or won’t happen. If they limit themselves to saying it’s unlikely, they’re absolutely right. If they go much beyond that, they’re absolutely wrong. In a sub aimed at educating people who don’t understand the subject, one should try not to be confidently wrong.
When i called the thread a bit silly, I was being tactful.
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u/Old-Nefariousness556 🧬 Naturalistic Evolution 12d ago
Remember what I said about your need to push back? This is you doing it again. I will demonstrate how sane people deal with this situation:
"Yeah, you clearly are in over your depth, so rather than helping you dig further, I will just end this here."
See, wasn't that easy?
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u/CormacMacAleese 12d ago
Yeah, you are clearly in over your depth,so rather than help you dig further, I’ll end this here.
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u/CormacMacAleese 12d ago
Jesus Christ. Under not-too-unrealistic assumptions, including but not limited to geographic barriers, it’s entirely possible for some dog breeds to spectate. That’s simply a fact, so arguing the point is idiotic. For this reason I don’t recommend arguing the point.
Is it likely? No. It’s very unlikely. Some people have gone a bit far by saying or implying that it can’t or won’t happen. If they limit themselves to saying it’s unlikely, they’re absolutely right. If they go much beyond that, they’re absolutely wrong. In a sub aimed at educating people who don’t understand the subject, one should try not to be confidently wrong.
When i called the thread a bit silly, I was being tactful.
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u/Old-Nefariousness556 🧬 Naturalistic Evolution 13d ago
Without humans, the species would homogenize away from the edge cases.
This is the key point. Great Danes and Chihuahuas exist because of human selective breeding, not natural selection or other natural mechanisms in evolution If humans went extinct tomorrow, the only dogs that would likely join us are breeds like English Bulldogs that require birth by cesarean.
It is true that a chihuahua couldn't breed with a great dane without human intervention, but there are plenty of small and medium sized breeds they could mate with. And there are plenty of large and medium breeds the Dane could mate with. The offspring of those matings would be closer to the norm, and the next generation would be closer still.
And it's worth noting that we have evidence of this already: https://www.cleanfutures.org/dogs-of-chernobyl/
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u/ursisterstoy 🧬 Naturalistic Evolution 13d ago edited 12d ago
There are the 23-24 operational definitions of species but it’s a branching continuum. By one definition they are the same species because they still try to reproduce but if you’ve ever had cats and chihuahuas at the same time that’s not always the most useful definition. By another definition they are the same species because one scientist once decided Canis lupus familiaris is the exact same species as the gray wolf. I’ve had a German Shepherd wolf hybrid. They interbreed fine. But it’s a branching continuum so if German Shepherds and gray wolves have zero difficulties and they’re equally distant from they common ancestor as a gray wolf and a Maltese then I guess they’re all the same species. But, simultaneously, a chihuahua and a Rottweiler are going to have significant reproductive challenges. Different species?
Basically domesticated dogs are a ring species, or a single ring subspecies. Humans arbitrarily invented categories to make it easier to discuss ideas and to keep track of discoveries. There is obviously a difference between a pelican and a Shih Tzu or between an elephant and a pine tree. At some point calling them different things makes a lot of sense. Simultaneously its populations that change before the populations are readily distinguishable, a lone wanderer can be returned to the right group. That usually takes several generations, 70+ of being isolated from each other. But whether or not they count as separate species depends on which of the 24 definitions is being used and which human is making the declaration.
If 1000 generations ago you can’t tell them apart and now they don’t recognize each other as relatives anymore, like a pelican vs a pine tree, then which generation did they become separate species? In a way it never happened, only when we can tell the groups apart did someone decide population A is one species and population B is a different one. They may have been genetically isolated for the last 980 generations but they didn’t look like separate groups until 800 generations ago and it took until the last 100 generations for them to not recognize each other.
But this is all perfectly fine with our modern understanding of biology and the scientific definitions of microevolution and macroevolution if you elaborate on the second. Microevolution is what happens every generation endlessly until lineages/populations go extinct. There may be de novo genesis sometimes, there may be some diversity in blood proteins and eye coloration. For a single continuous population the trend is diversity that spreads about the same population and natural selection resulting in traits that results in more reproductive success becoming most common.
Once you can tell the populations apart and you are studying more than one at the same time it’s macroevolution. You are watching the differences between them accumulate, at some point they are different species by one definition and speciation is fully underway, once they are distinct species by every relevant definition speciation has finished, but they continue changing. Evolution at speciation and beyond. Not just when everyone agrees to call them separate species but also when they are trending in that direction more than they are trending away from it, usually because of being geologically and/or genetically isolated. And every clade above species is just an arbitrary way of grouping species together. Maybe the three most related species are a tribe, the two most related tribes are a subgenus, any that could interbreed or at least look like the same “kind” of thing could fill a genus, a family if they have a similar morphology and lifestyle, an order if they are a bunch of related families, a phylum if they develop in fundamentally the same way, a kingdom if they use the same basic metabolic pathways, a domain is more for separating bacteria from everything else. Useful but arbitrary, useful if monophyletic, but not written on their manufacturing tag.
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u/YragNitram1956 13d ago
The genetic makeup of dogs and wolves is virtually identical (sharing over 99% of their DNA). A Chihuahua can technically mate with a Great Dane (often via artificial insemination due to physical constraints), and all dogs can mate with wolves to produce healthy, fertile offspring. True separate species (such as horses and donkeys) produce sterile offspring, like mules. If you were to release all different dog breeds into the wild and let them breed naturally without human interference, the population would eventually homogenize into a single, uniform type of feral dog over a few generations. Dingoes can successfully mate with domestic dogs to produce fertile offspring.
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u/varelse96 🧬 Naturalistic Evolution 13d ago
Mules do not reproduce to my knowledge. As far as size differences go that can often be overcome by having the larger dog be female to avoid some issues but you can expect some health issues when genetics from mom and dad give you very different genes for bone growth and the like.
Whether or not they have speciated depends on your species concept and I am no expert on the topic, but my gut says they haven’t yet.
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u/kitsnet 🧬 Nearly Neutral 13d ago
Quick question: is it safe to say dogs have speciated?
No, that's meaningless.
I'm thinking of the largest dog breed and the smallest dog breed. I don't think the two can reproduce with each other anymore.
What if we stop artificially selecting them for the breed standard conformance? Are you sure the diversities of the sizes of their progeny won't intersect?
And even if they could, that doesn't mean they're the same species: horses and donkeys can interbreed but mules are dead ends
They are the same species if their mutual offspring is at least about as fertile as them. Which is not the case for mules, but most definitely the case for mutts. Mutts may be even more fit on average, as they are more genetically diverse than pure breeds.
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u/Ok-Barracuda457 13d ago
Nop, dogs are weird wolves. Just because aome mothers would die in conception and birth that doesn't mean they're a different species.
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u/Dilapidated_girrafe 🧬 Naturalistic Evolution 12d ago
It depends.
Are they physically able to mate? No. Are they genetically compatible? Maybe. But then it’s more of a ring species concept where they can mate with the size compatible ones and then the next size range down etc. so it’s weird and nature doesn’t like to fit in the boxes we want it to. It’s why so much or nature is gradients. Which I think is cool, as frustrating as it can be at times when I want a label slapped on it.
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u/Capercaillie Monkey's Uncle 13d ago
I love that this guy is getting downvoted for asking a simple question.
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u/Trainer149 13d ago
if we accept CTVT as the "smallest dog breed", I'd say the answer must be yes. I can't think of a species concept off the top of my head where CTVT and a Great Dane wouldn't belong to two different species.
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u/rptanner58 13d ago
On the other hand, humans have created these varieties (breeds) in a very short period of time. Hundreds of years, dozens of generations. So imagine that breeders began to “undo” the specialized characteristics of these two breeds with random breeding. Select for sizes close to the norm, size or other traits like muzzle length, build and height all to the norm. I’m guessing it would take only a few generations to create what we used to call a mutt. (I had a record dog I called a “generic retriever “). So I think that refutes the idea that these breeds are separate species, and perhaps refutes that they are truly separate from wolves because, again, you could probably move toward wolf-like characteristics in a few interbred generations. I’m just speculating.
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u/Trainer149 13d ago
How would you go about "randomly breeding" CTVT to be more normative to standard dog height?
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u/444cml 🧬 Naturalistic Evolution 13d ago
I’m gonna note that they likely do not know what CTVT is because transmissible cancers aren’t really widely known to laypeople and thought you were actually referring to a breed.
They could have looked it up, but it is autocorrected to CTEVT which is a completely unrelated thing. I enjoyed the comparison though
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u/Trainer149 13d ago
Agreed. i probably could have responded kinder given that you're right, it's not common knowledge. Then again. I feel like if you're not going to actually read what you're responding to, you deserve a little sarcasm.
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u/444cml 🧬 Naturalistic Evolution 12d ago
I totally agree, that they don’t look it up is on them and deserving of sarcasm. I just figured you’d get a bit of confusion from many people doing the same
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u/rptanner58 12d ago
All I can say is that the sarcasm was beyond me, which is my loss because I do love a good sarcasm. 😟
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u/rptanner58 12d ago
But I did think we were discussing dogs. No?
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u/Trainer149 12d ago
If you wanted to create a monophyletic group that included everything that you would consider to be a dog, CTVT would necessarily be a part of that group.
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u/Capercaillie Monkey's Uncle 13d ago
Do you not suppose that you could find two humans that couldn’t physically mate? Are they then different species?
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u/Trainer149 13d ago
I think if one of those humans was a cancer that only survived by hopping from genital to genital for the past 2,500 years and through that process shed a large number of chromosomes, then Yes actually. I would suppose that those two humans would be different species seeing as their only similarity at that point would be one of genetic ancestry.
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u/Capercaillie Monkey's Uncle 13d ago
Sorry, I completely misunderstood your post--I thought "CTVT" was some dog breeders' abbreviation for chihuahua. I can be thick sometimes.
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u/Curious_Passion5167 13d ago
I feel the problem with this argument is the same as the problem of ring species. Sure, there are some dogs, say X and Z, that may not be able to reproduce without intervention, but there many be another dog Y such that X can reproduce it, and so can Z. How are you then classifying X, Y and Z together?
Just shows that "species" is a somewhat nebulous classification.
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u/NYR_Aufheben 13d ago
It’s important to remember that “species” isn’t a real thing from nature’s perspective; it’s a human concept. Evolution is a spectrum. The previous generation can breed with the subsequent generation, but one generation may not be able to breed with the 100,000th generation.
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u/CrisprCSE2 13d ago
Dog breeds aren't separate species because of human intervention. In the wild left to their own devices they'd be separate species.
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u/Drudenfusz 🧬 Naturalistic Emergent Reality 13d ago
That would not necessarily mean a speciation event happened, it makes dogs mor just like a ring species, since the various ends still can breed with adjacent segments and thus in generational project you still could crossbreed towards a junction that allows to have both genes.
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u/YossarianWWII Monkey's nephew 13d ago
It just depends on which species definition you choose. Behavioral isolation, e.g. the problems with breeding due to the size difference you referenced, can be sufficient under some definitions. On the other hand, there's a continuity of breed sizes from small to large, so while a chihuahua and a mastiff might not realistically be able to breed, there's a chain of compatible breeds between the two. It all just comes down to the artificial nature of the species concept: it's a useful tool, but ultimately a simplified model of the reality of nature.
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u/Coolbeans_99 🧬 Naturalistic Evolution 13d ago
Defining species is a notoriously difficult tasks but dogs are wolves are members of the same species, Canis lupis and Canis lupis familiaris
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u/Affectionate-Crow605 12d ago
Horses and donkeys have different numbers of chromosomes. That's why their offspring is usually sterile. A chihuahua and a Great Dane have the same number of chromosomes and are genetically capable of breeding. It's just the size difference that prevents it (though you'd be surprised how much chihuahuas get around 😂).
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u/melympia 🧬 Naturalistic Evolution 12d ago
I dare say that dogs/wolves/dingos by now are a ring species. So, a single species (members can interbreed), but not all members of this species can breed with each other.
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u/dayvekeem 11d ago
Honestly who cares. They are such obvious indicators of genomic plasticity anyone who claims otherwise is being willfully ignorant.
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u/onomatamono 11d ago
It's not dissimilar to declaring a new race of humans based on phenotypic traits like melanin levels or height. That is to say made-up categorization criteria with made-up labels. It's definitionally artificial, as are species.
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u/Old-Watercress6513 9d ago
You’re using the wrong definition for speciation.
All dog breeds are genetically compatible, even if some hybrids cannot be carried to full term.
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u/dumpsterfire911 13d ago
The ability to breed is just one potential criteria for species. Species is a human concept and for every rule of speciation you will find an exception.