This isn’t necessarily the case, but I think it may often be true.
Most artificial selection works on existing genetic diversity in the wild population, pushing the phenotype quickly to the extremes of what’s possible with the existing genes, without requiring new mutations. And then those extreme phenotypes are inbred, removing the diversity. So if (for example) the only dogs that existed were chihuahuas, and you tried to breed large chihuahuas by crossing chihuahuas with chihuahuas and picking the largest of the litter, I don’t think you’d get very far. The diversity is gone. But in reality, there’s a pretty wide diversity of breeds, so there might be quite a lot of genetic diversity in mongrels. Dogs might be one of the more diverse domesticated animals if you include the diversity present all the various breeds.
With other domesticated species like farm animals, where there isn’t the aesthetic desire that we have with pets to maintain a diversity of breeds, it may be that a lot of the genetic diversity in the wild ancestors is just completely gone through inbreeding.
Wouldn’t the proper classification be “Family” instead of “Species”? According to the chart I copied, the animals you mentioned would be different members of the same Family, but one distinct species.
Dogs are classified as follows:
Kingdom —Animalia (note the Latinized spelling)
Phylum —Chordata (presence of a nerve cord along the back)
Class —Mammalia (presence of hair, milk glands)
Order—Carnivora (meat eaters)
Family—Canidae (dog family)
Genus, species** —Canis familiaris.
Is it now thought dogs were only domesticated once, and spread? I thought it had been believed they were separately domesticated by several groups of people.
I think you are being misled by the common names. The family Canidae includes animals variously called dogs, wolves, jackals, coyotes, and foxes. It’s best to refer to them in general as “canids.” The names “dog” and “wolf” have no taxonomic meaning (although “fox” sort of does). Although the animals I listed are all called “dogs,” they are not closely related to one another besides being members of the same family, and are mostly not closely related to domestic dogs.
The African Wild Dog is in fact fairly closely related to Gray Wolves/Domestic Dogs. However, Bush Dogs and Short-eared Dogs belong to a South American group of canids that also includes the weird Maned “Wolf,” which is not related to Gray Wolves. The Raccoon “Dog” is actually a kind of fox.
Don’t get me started. Dog genetics is pretty much a dog’s breakfast. It seems every few months a new study comes out contradicting or challenging previous studies. As far as I know, there is no generally accepted consensus on the issue.
The domestic dog lineage apparently diverged from Gray Wolves sometime between 40,000 and 20,000 years before the present. Gray Wolves underwent a population bottleneck about 25,000 years ago, and most populations aside from one in Beringia went extinct, presumably including the one that was ancestral to dogs. Gray Wolves later expanded their range again into areas they previously inhabited, including the one inhabited by ancestral dogs.
Dogs were domesticated at some point after their ancestor split from other Gray Wolves. The oldest undisputed Domestic Dog fossil dates to about 14,000 years ago, although much older ones have been claimed. There are claims that domestication took place in Southeast Asia, Central Asia, Southwest Asia, and maybe Europe. Some have claimed that there is evidence for at least two separate domestication events. However, I’m not sure what the current state of play is on this subject.
IMO, it is likely that dogs underwent various degrees of domestication at different times and in different places. However, I don’t know that this has left any clear signature in modern dogs. The situation is complicated by the fact that hybridization events since domestication have lead to the introduction of wolf genes into dog populations (and of dog genes into some wolf populations). This is analogous to the way Neanderthal and Denisovan genes have been incorporated into some but not all regional populations of modern humans.
That kind of looks like a speciation event, separating dogs from wolves. If no humans were involved, a species that split into two geographically separated sub-populations (Beringia vs non-Beringia) and developed different morphs (“gray” vs “yellow”) would sometimes be called separate species. Of course, humans were involved, and multiple cross-breeding make it not very clear.
That’s true. Since domestic dogs and Gray Wolves are reciprocally monophyletic, the argument could be made that they should be classified as separate species. However, the split is much more recent than most forms that are currently regarded as separate species. For example, Polar Bears and Brown Bears are one of the most recent species splits, and they diverged 500,000 years ago. Given the recent divergence and frequent hybridization it’s probably best to classify dogs as a subspecies of Gray Wolf.
While different breeds of dogs have a wide variety of different traits, there are still some traits they have in common. If you let all the dogs out and let them mix, well, you’ve got chihuahuas and St. Bernards (and Jack Russels and Great Danes and beagles and Labs and everything in between), so you probably could revert to wolf size (including natural wolf variation in size). But all of those breeds have been bred extensively for docility, and so no matter how many breeds you mix together, you’re always going to get something more docile than a wild wolf.
True for Denisovans, but the current data seems to support Neanderthal incorporation into every regional population, including more remote African ones like San Bushman.
I suspect so, too. Looking at the links that @Colibri provided to the feral dog breeds, they all look a lot like your stereotypical “just a mutt” dog, and are somewhat smaller than wolves.
This is speculation, but the tendency of mutts to converge on the “Yaller Dog/Dingo” phenotype could be due to the fact that different genes have been selected for in different breeds, and other breeds retain the ancestral allele. If you cross different breeds, you may end up with an animal heterozygous for the ancestral allele at most loci, and if that trait is dominant the animal will look like the ancestral form. In feral populations, over several generations the more extreme phenotypes from domestic breeds, being less compatible with survival in the wild, will be selected out.
Dog genetics is pretty much a