Natural History

It’s not unusual for people who are trying to deny evolution or promote creationism or both, to come up with a common question:

“If evolution is true, then why don’t dogs have something that isn’t a dog every once in a while?”

This question would not be so much of a problem if we, who think we know better, would stop trying to create a species called Canis familiaris.

Canis familiaris made sense when we didn’t know what dogs were derived from, and it might have made sense if we thought there were hard and fast reproductive barriers between dogs and wolves.

But it turns out that they really aren’t such distinct animals. We’ve learned this when we’ve performed more complete assays of domestic dog and wolf genomes. Since then, we’ve found that the majority of Eurasian wolves have some domestic dog ancestry, and black wolves in North America got their black coloration as the result of a single cross with a black dog that mated with a wolf thousands of years ago in the Yukon or Northwest territories.

A recent genome comparison study of wolves and dogs that attempted to put together a phylogeny of the species clearly states:

[W]ithin the Old World clade, wolf and dog represent sister taxa. Therefore, suggestions that the dog or dingo are a separate species (Canis familiaris) (e.g., Crowther et al. 2014) would cause gray wolves to be a polyphetic taxon; and consequently, our results support dogs as a divergent subspecies of the wolf. This result has societal significance as legislation in some countries and regional governments consider wolves and dogs as distinct species restricting the possession, interbreeding, or the use of vaccines and medications in wolves or dog–wolf hybrids if they have only been approved for use in dogs. In this sense, analysis of evolutionary history informs law and veterinary practice, as dog lineages are nearly as distinct from one another as wolves are from dogs, and the justification for treating dogs and wolves differently is questionable.

The monophyly of the species is one thing that I think everyone should agree is worth preserving in any taxonomic system, but the genomes clearly show that if we create a special species for the dog or the dingo, we wreck the monophyly of Canis lupus.

I would also contend, perhaps a bit more controversially, that in light of a similar study of North American wolf-like canids’ genomes, that the coyote is also part of Canis lupus. This study found that gray wolves and coyotes have exchanged genes across North America and that gray wolves and coyotes last shared a common ancestor only around 50,000 years ago. That ancestor was probably an ancient Eurasian gray wolf that came into North America and evolved for a more generalist, jackal-like niche in the mid-latitudes of North America.

When someone claims that dogs are not wolves, they can only mean it in the same way that pugs are not Siberian huskies or that Great Danes are not dingoes. They are not wild Canis lupus, but they clearly are within that species, if we wish to keep the species monophyletic.

The reason why people want to claim a special species for the dog is because of Raymond Coppinger’s ideas still hold a lot of sway with people who wish to be learned about dogs. It’s not that everything that Coppinger said was wrong. It is what he was wrong about seems to be all that people know.

Coppinger argued that domestic dogs were obligate scavengers and thus must be placed as their own ecological species. An ecological species is the best argument for Canis familiaris. But it has limits for our understanding of evolution, and it can be turned into an absurd concept. For example, there are two sharp-tailed grouse subspecies that live in slightly different but adjacent habitat but do not readily interbreed. If we were to adhere to the same sort of species concept, then these two subspecies would have to be distinct species, even if it busted up the entire monophyly of the sharp-tailed grouse species.

Coppinger is ultimately quite wrong about the obligate scavenger status for domestic dogs. In India, for example, predation by feral and free-roaming domestic dogs is a major conservation issue. And Italian wolves are big time dump denizens. So both dogs and wolves can be predators or scavengers based upon available prey and refuse resources.

Because the ecological species concept is muddled when comparing wolves to dogs and keeping an arbitrary Canis familiaris species destroys the monophyly of Canis lupus, it would make more sense to drop Canis familiaris entirely.

One could raise dogs to Canis lupus familiaris, but Raymond Pierotti and Brandy Fogg have argued in their book, called The First Domestication: How Wolves and Humans Coevolved, that there is no set of behavioral, physical, or physiological traits that define all dogs as a taxonomic entity. They instead argue that we should just call them “domestic Canis lupus,” in which they also group the dingo, which is “feral domestic Canis lupus.“

I remain agnostic about what we should call dogs, but Pierotti and Fogg’s quibbles are difficult to ignore. Perhaps we could have the subspecies for the dog, but there must be some acknowledgement that all we are doing is defining a domestic and feral population of a species.

If this blog post looks familiar, I wrote almost this exact same post in March, but I sometimes feel that I have to explain the very real scientific reasons why we don’t say that dogs are a unique species. It is not anti-science to do so, despite what Facebook dog experts tell you. If we want a monophyletic Canis lupus, then dogs have to be part of it.