People breed animals to create a line with distinct physical features, though still part of the same species.
Are breeds a purely artificial construct, or do animals in nature split into breeds? Would that be the first step towards one species splitting into other species?
And while we’re at it, why haven’t isolated human cultures evolved into a separate species? How many generations would it take for an isolated group to split off as a separate species?
No, breed is a term used to refer exclusively to artificial populations. The natural equivalent to a breed is a form, race or subspecies. Forms, races and subspecies are extremely common in nature. Any species that occupies a reasonably large geographic zone is almost certain to exist in multiple true breeding forms.
It can be. More often it is the equivalent to human races, IOW limited geographic isolation coupled with regional selective pressures mean that only certain phenotypes can survive in certain areas. Although influxes of genes from outside do occur they are so severely selected against that they never become common enough to prevent true breeding.
For example many there are desert forms of plants exist as small shrubs with small leaves. This form is genetically determined, and even when grown under optimal conditions the plant continues to exist as a shrub with small leaves. Exactly the same species exist in more humid climates as trees over 20 metres in height with large leaves. This is also genetic, but when this form is planted in desert areas it inevitably dies before maturity, thus ensuring the genetic types remain true breeding.
Quite simply because no human population has been isolated for anything like long enough. The longest period of genetic isolation of any human population has only been 10, 000 years. Remember humans have a very long generation time, 20-25 years. That means that 10, 000 years is only 500 generations. We’ve seen rabbit populations on islands that have been isolated for well over 500 years, which in evolutionary terms is far longer, and they haven’t shown any signs of speciation.
There is no fixed time required for a population to speciate, but it does require long enough for a mutation that prevents interbreeding to both evolve and spread to 100% of the population. The odds of that happening in 500 generations is astronomical.
Speciation in mammals is generally harder than in most other species anyway. While they may show a distinct mate preference mammals are extremely flexible in mating when there is no choice. The hardware of mammals is also very adaptable. As a result you basically need total genetic or geographic isolation for speciation to occur. In other species you can get speciation simply by introducing minor changes in breeding season or the courtship dance the shape of the penis and similar trivialities. Those types of changes can occur fast and the populations can then be geographically mingled again and yet remain genetically isolated.
With the propensity of some humans to have sex with anything that moves you need true isolation for speciation to occur, and that just hasn’t happened for more than a few hundred generations.
It seems likely that the Australians were isolated from the rest of the human species for something on the order of 50,000 years and no speciation has occurred. The native Americans may have been separted for 15,000 years, possibly even longer (a considerable controversy over that).
But certainly varieties (= subspecies) occur in nature. The most interesting example is a so-called ring species. There are two non-interbreeding groups of common gulls in England. (I don’t know if they cannot breed or simply do not. Perhaps they can breed with difficulty and don’t usually.) They would normally be considered two separate species since they occupy overlapping ranges and don’t interbreed.
But, as you move west to Ireland, Iceland, Greenland, Canada, Siberia, Europe, then England again, you have a continuum of minor varieties ringing the pole untl you get back to England and find the other species.
I had read about that a number of years ago. In Dawkin’s “The Ancestor’s Tale”, he describes another which is a ring species of snail that live halfway up a mountain that rings a valley in, I think, California.
This all illustrates that the notions of species and variety are not clearcut. Even less so are higher taxa.
BTW, as a mathematcian I would be tempted to describe a ring species as a Riemannian species, but that is an in-joke.
Can we have a reference for that claim?
As far as geneticists, archaeologists and anthropologists have been able to tell he Australians as a whole have probably never been isolated for more than 500 or so. Technology, domestic animals, genes and individuals seem to have been making the crossing between Northern Australia and Indonesia non-stop for the past 60, 000 years.
Tasmanians were isloated for somehere betwen 10 and 12 thousand years, the longest isolation of any human population.
Once again, I’ve never seen any suggetsion that North Americans were isolated for anything like that period of time. The first Native Americans probably arrived around 10-12, 000 ybp, but I don’t think I’ve heard anyone suggest they remained isolated from the moment the stepped ashore. Indeed I got the impresion that scientific consenus was that there were at least three separate migrations spread over 4000 years or so. Morover it seems likely that constant low level contact by indivdiuals or small groups was occuring betwen Siberia and North America more or less constantly.
I’m just here to repeat the above. It’s all a matter of semantics. If which animals breed with which animals is governed by chance, geography, and random opportunity–i.e., nature–it’s called natural selection. If such selection is a product of human intervention, it’s called breeding.
Same result, different impetus. It’s conceivably possible that if breeding were consistently applied for long enough–millions, at least hundreds of thousands–of years, then speciation might conceivably occur.
So yeah, same mechanism; difference lies only in impetus and semantics.
Well, if humans were beeles, then some of the various “populations” would be considered seperate species or sub-species. That’s mostly because the beetle biologists are perhaps the most notorious “splitters” in the profession.
Some of the human populations were perhaps on their way to becoming subspecies. Tasmanians, Ainu, the peoples we call “pygmies”, and so forth. Neanderthal man was a sub-species, most now say.
You *could *call some of the various human populations (they don’t like the “race” word anymore, and it’s not very precise) “breeds” if one defines breed as a “member of a species that differs by external appearances, breeds true and does not rise to a sub-species in differntation”.
Do you mean the Salamanders?
(I haven’t yet read “The Ancestor’s Tale;” it’s on the to-read list.)
I find that very hard to believe. Can you provide an example of some beetle populations that intergrade completely, have never been geographically isolated ,are completely interfertile and have no significant genetic differences between the populations that are considered to be separate species or subspecies?
No, that simply isn’t justifiable in any way whatsoever.
Everybody always said he was a separate subspecies at the very least. There was a brief period when he was considered not be a a completely seperate species.
Yes, and if you say taht a tail is a leg then a dog has 5 legs.
I agree with all the posts above, except Hari Seldon
Not to be pedantic but Australia as a country has only been in existance for 218 years - shorter if you take it from Federation in 1901 - prior to which it was Gondwanaland or Terra Australis. Australians are the modern inhabitants of this land. The traditional owners are collectively known as Aboriginals or Koori’s.
As other posters have said - it was definitely a fluid migration because for much of those 50, 000 - 100, 000 years, Gondwanaland was accessable by ‘land bridge’ and boat. Indonesia and Papua New Guinea have never been very far away!
I would like to add however that there is, for want of a better term, a ‘naturally occurring breed’ of cat called the Maine Coon. Although this cat is selectively bred by cat breeders for its traits, it was a type of cat that naturally occurred in the New England regions of the United States (hence Maine Coon) and also occurs in other similar climates. It has long, thick fur on its body and underbelly but short fur on its head and neck so it can slip easily through the underbrush but be protected from the snow. To this end it also has long fur between the pads of the paws that act as snow shoes. They all have a line that extends from the corner of the eye to the side of the face (hence Coon i.e raccoon) and come in all different colours yet share similar personality traits.
Although some breeders say that unless you got it from a breeder it is not a Maine Coon, I had a cat of this ‘breed’ that came from the local RSPCA (Royal Society for Prevention of Cruelty to Animals - don’t know what the US equivalent is) and had been part of a litter that was mixed with no other similar cats and the mother was a Tortie. Don’t know what the father was. Yet she shared all the physical and personality traits common to this ‘breed’ without having been ‘bred’. We do have a New England region in Australia which is in north east New South Wales and while it doesn’t snow the temperature is quite cold. Obviously the Maine Coon was introduced here but it does also occur in England.
Just thought I’d add that one to the mix.
Actually, I can think of at least three instances of what could be called ‘breeds’ in nature.
They are seperate species, but they call all interbreed with each other, and one of the species shares geographical areas with the other two. (But not all three at once.)
This is a rather rare case of populations becoming seperated by social, or behavioral, barriers, not geographic ones.
The three species are Canis latrans, Canis lupus, and Canis rufus. Or, in terms that will be more familiar: The coyote, the grey or timber wolf, and the red wolf. A few years ago, there was a bit of a huff when it was found that the current population of Canis rufus was actually a hybridization of the strains of coyotes and timber wolves.
While they are basically “dogs” I think it’s quite fair to consider them as meeting the requirements of the OP.
They are seperate species, just with unusual barriers for cross pollenation.
And, no I can’t. No one but a beetle expert can, but they are known for this propensity. An arboreal beetle that lives in one tree with 3 red spots will be considered a different species than a nearly identical beetle in another tree- but who has 4 red spots.
Some species can interbreed just fine, thank you- but are still generally considered different species**- OtakuLoki ** mentions Canis. The problem is- people- even Biologists- can’t look at their own species with dispassion. Any discussion of "race’ or “sub-species” *vis-a-vis * Humans gets too many hackles up. Case in point, your posts.
In your opinion.
No, for quite some time Homo Sapiens Neanderthalensis was simply Homo Neanderthalensis- in other words, he was considered a separate species.
Yes, in *your * definition of “breed” as an artifical construct. Biologically there is no significant difference between a "breed’ and a “population” or even a “sub-species”.
But they’re never referred to as ‘breeds’. Blake is quite correct that that the term is generally reserved for deliberately human-bred animals.
For that matter ALL Canis are probably capable of interbreeding - they just don’t as a rule. Doesn’t make them breeds. They’re generally good species.
Including, it would now appear, the red wolf. I believe the latest research has pointed back to the traditional assumption and the gray wolf/coyote hybrid swarm hypothesis is now on the wane.
I thought the jury was still out on this one. Granted I don’t follow physical anthropology as much these days.
Well, but that IS the definition :). I agree that that terms like “race” , “morph” and “subspecies” asre all rather fuzzily defined place-holder terms for groups that may or may not have much biological reality to them. But the term breed does have a strongly implied artificiality to it.
Sorry, not artificial, but human mediated.
Keep in mind that there’s no such thing as “species.”
A “species” is an artificial concept, part of an artificially derived system of organization, used by fallible scientists as a way to categorize an essentially uncategorizable world.
Though it’s generally a given that ignorance of the law is no excuse, I think we can give the individual members of *Canis *a pass. They don’t know they’ve been designated as species, so they don’t know they’re not supposed to interbreed. Many reputable scientists insist that *Canis *has been wildly mis-categorized, using many of the examples listed above as support for this notion.
IANARS, but I agree with this. The standard organization of the genus *Canis *is insupportable. It’s believed that different breeds of dog have evolved from different supspecies of wolf, in different parts of the world. To suggest that a parent species split into several supspecies, but that each of those supspecies gave rise to isolated populations of a single common species, is ludicrous. It’s all just an outrageously convoluted attempt to avoid classifying the Dog and the Wolf as one single species, which would fly in the face of a lot of cultural baggage. To mix my metaphors.
But since taxonomy is just as much a human construct as the cultural baggage, I for one am a little puzzled at why this hasn’t been done, officially.
It’s not just that- note that Tigers & Lions can interbreed. True, they only do so in zoos, but still- they are clearly different “species”.
Until recently, it was thought that the 3 Canis spp did not normally interbreed in nature (and in fact, it is possible that until Humans can around, they didn’t). Thus, species. Thought has been given to making them sub-Species instead, which might reflect more of what we now know.
Most anthropologists consider Neanderthals to be a distinct species. But it’s not like there will ever be a definitive answer. Species classification has a certain amount of subjectivity in it, so it’s unlikely that there will ever be universal agreement one way or the other.
Would Saugeye or Tiger Muskie count?
IOW there is no factual basis for your claim. Unless you are claiming that an example exists of where beetles in an intermediate tree have between 3.2 and 3.8 spots?
This is the reason your suggestion is ridiculous. All human populations intergrade perfectly, I am well aware of taxonomists who want to split every form of of a species into anew subspecies, but not of cases where they wish to do so despite well documented and irrefutable intergradation of forms.
Err, yes? And what point are you attempting to make here? Has anyone suggested otherwise?
Sigh. No. We are discussing the facts here. Your posts were pure nonsense with no factual basis whatsoever, as we have discovered, having asked you to provide those facts.
Why is it that when people make ignorant claims pertaining to race and someone calls them on it the first thing they all do is accuse the challenger of being PC or oversensitive?
Look Bub, this is the SDMB, we are supposed to be fighting ignorance. This is GQ, we are supposed ot be constructing factual answers. Your claim that “human populations were perhaps on their way to becoming subspecies” is both if\gnorant and counterfactual.
The only reason my hackles are even slightly up is because you are spewing ignorant garbage all over the boards.
No, as a matter of fact. Your claim that " human populations were perhaps on their way to becoming subspecies" is ignorant rubbish.
“genetic interchange was constrained by isolation by distance so that human populations living in different geographical areas would be genetically differentiated. The gene flow was sufficient, however, such that the major races of humans do not constitute evolutionary sublineages of humanity.”
Templeton, A.R., 1997, Out of Africa? What do genes tell us? Current Opinion in Genetics & Development, 7
The time has come for you put forward your evidence that indicates a possibility that some human populations were on their way to becoming subspecies.
That is exactly what I just said. You do realise that organisms of a separate species is, by extension, also a separate subspecies? Just as organisms from separate genera can’t remain in the same species?
Biologically there is significant difference between a breed, a population and a sub-species.
A population is a sample space and nothing more is implied beyond that. Hence New Yorkers are a biological population, as are black New Yorkers. Populations can and inevitably do overlap and intersect. There is no implication of biological coherence within populations.
A breed is, as already noted, exclusively refers to artificially engendered phenotypes. That’s a pretty significant difference don’t your think?
As sub-species, while being a somewhat fuzzy unit is created under an assumption of both biological coherence and natural production.
I hope that you never have to publish anything on population dynamics if you don’t believe there is a significant difference between those terms.
Blake. You’re no rookie here. This is General Questions. Let’s keep it a bit more civil. OK?
samclem GQ moderator