The post below on the genetics (and relaxation of constraint) of dogs has given rise to many good comments. I want to highlight one:
...Yet most feral dog populations quickly revert to a medium-sized, short-coated, yellowish dog - the so-called "Pariah Dog" that's found in so many places around the world - why don't the feral populations look more like their wolf ancestors?
There are many issues mooted below. But this comment is a good one. Why do dogs "revert" into pariah dogs instead of the Eurasian wolf? Remember what is happening here: being as "cute" as a poodle doesn't matter once you're a stray (at least unless you are adopted because of your cuteness), so the less cute dogs with skillz do better in the game of life (reproducing). And yet dogs do not quite turn back into the wolves from which they derived. Why not?
One could argue that the most plausible explanation is that a) the niche of Eurasian wolves is already taken b) a new niche, that of canines which live as "urban wildlife" has opened up. But, I think there might be theoretical issues which might offer us insight into what is going on, and that insight is the Shiftling Balance (see here for a good review). The manner in which the Shifting Balance might apply is that "breeds" might be thought of as local populations, and this sort of substructure is essential for the sort of evolution which Sewall Wright envisaged.
The Eurasian wolf may be assumed to be a large mixing population which is "stuck" at a fitness optimum. In contrast, dogs, artificially constrained into separate populations, allowed to "explore" a greater expanse of the adaptive landscape, can find new fitness optimums. When human selection is relaxed the nearest "wild" fitness optimum might not be that of the Eurasian wolf, a top niche predator, rather, the skillz of the domestic dog lend themselves to living as scavengers around human habitations. Please note that the Shifting Balance is not just about random genetic drift swamping the power of selection, rather, it also implies the bringing to fore gene-gene interactions as prior selection on loci are relaxed. One might conceive of the domestic dog as a new "coadapted gene complex."
Of course, please do remember that the Shifting Balance is better metaphor than formal theory. But, I do think conceiving of evolutionary dynamics in this manner is a good place to start, a way to bridge the chasm between formal population genetic theory and the public discourse around evolution.
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Good question and a good answer. Another point: has the dog diverged away from the wolf enough that it CANNOT revert to the wolf form any more just due to being too different?
CANNOT revert to the wolf form any more just due to being too different?
yes. that might be it...though my own hunch is that the interfertility of dog breeds suggests to me that there is still the physical possibility (that is, if you tilted the landscape a wolf could be extracted out of the landscape).
Wild dogs probably function more like coyotes or foxes than like wolves.
The Australian dingo is presumably the bext example of a truly wild feral dog. Is it more wolf-like or pariah-like?
"Pariah dog" can either mean an actual breed of wild dog in India, any stray dog in India, or wild species from elsewhere who are thought to be similiar to the Indian wild breed. In other words, it's more like a folk term than a scientific term.
The "Canaan Dog" is white but looks pretty wolflike.
A lot of the differences between generic mutts and wolves are size, fur color, and fur thickness, and these are among the most easily modifiable traits. One trait that came up when I was googling around was a short muzzle (wolves, as opposed to foxes and coyotes). This seems like a better marker to track.
http://en.wikipedia.org/wiki/Canaan_Dog
http://en.wikipedia.org/wiki/Pariah_dog
There is apparently an indigenous American non-wolf wild dog:
http://en.wikipedia.org/wiki/Carolina_Dog
The German site has a picture:
http://de.wikipedia.org/wiki/Carolina_Dog
Close to human habitats, trying to be an apex predator is going to be a losing game - humans don't take kindly to direct competition. Instead the niches available is probably closer to that of an opportunistic scavenger, like rats, pigeons or cats. In other words, as John and David point out above, a niche closer to the dingo, coyote and the fox (all of whom, I believe, live in the "shadow" of dominant predators). And when you scavenge the spoils of a dominant species, being quick, smart and not too large is what matters.
Just a follow up on my original post -
To my eye, the Canaan dog, Carolina dog, Pariah Dog, Dingo, etc, all have certain common characteristics which are more 'dog-like' than wolf-like" in appearance. Look at the picture of the Canaan Dog here: http://en.wikipedia.org/wiki/Canaan_Dog , and then this picture of Dingo here:http://en.wikipedia.org/wiki/Dingo. They look pretty similar in my mind, at least phenotypically. Sort of a proto-dog - or the dog that feral populations revert to after several generations. Indeed the Wikipedia entry more or less claims that the dingo is kind of an 'ur-dog" which makes sense to me. http://en.wikipedia.org/wiki/Dingo
To follow upon Razib's original comment to my query, I think it's quite plausible that the original cohort of wolves domesticated in East Asia must have been quite small in number - AND - must have displayed some neotonous qualities that not only made them domesticatible, but also considerably altered their appearance (shorter muzzle, more rounded ears, etc). If this group of domesticated wolf descendents were left to breed on their own in the mountains of the Carolinas for several generations or in the Australian outback - might it be that they can only 'revert back to a semi-neotonous predator? i.e., one that looks more dog-like than wolf-like? http://gator.biol.sc.edu/dogpage/ In other words, unless there's some sort of mutation to 'remove' the neotonous elements, dogs can't revert back to wolves, because of that genetic shift. It would be much like the Russian neotony foxes - http://www.americanscientist.org/template/AssetDetail/assetid/15642 - suddenly turned out in the wild in an area without contact to a wild fox population - would they indeed be 'able' to revert back to their ancestral form? Perhaps not. Comments?
To further this line of thought, has there been any research into the genome of northern sled dog breeds (Malmutes, Huskies, etc) might have more 'wild' wolf markers? They look a lot more 'wolf-like' in appearance and look a lot like various dog-wolf hybrids.
Anyway, this brings up another question - has anyone identified an actual set of genes that result in more juvenile appearance or neotonous characteristics? I think some one should look at the genomes of, say, Gary Bauer http://rightweb.irc-online.org/profile/1022 and Arnold Schwarzenegger http://www.schwarzenegger.se/planethollywood.htm and see if some of those genes couldn't be isolated??