Thursday, January 24, 2013

From wolves to dogs: a diet of domestication

I have two dogs, a mutt and a pure-bred Siberian Husky. The mutt---named Ranger, from the Latin Powerus Rangerus--is mostly Lab, though he might have some Boxer in him as well, along with who knows what else. We got him from a shelter some years ago (he's about 9 or 10 now, I think). He's lovable, but not particularly bright. The Husky--Shadow--we got from a Siberian Husky rescue org in Florida (people often buy Huskies as puppies, not knowing their needs as adult dogs). She's wicked smart and a stone cold killer, when it comes to animals--any animals--entering our property without permission. And she's still quite young (5 or 6).

My youngest one has decided, however, that we only have one dog (my wife would like us to have zero, by the way): the mutt, Ranger. For according to her--she's five--Shadow is not actually a dog. Shadow is a wolf. And of course, Shadow does look quite wolf-ish, being a Husky and all, because Huskies are one of the oldest breeds of dogs in the world. And they were bred as working dogs, for strength and stamina, so it's no wonder their wolf-like qualities have persisted, since we know that domestic dogs--all of them, every breed--are descended from wolves.

Still, the question of how exactly domestic dogs evolved from their wolf forbearers remains an open one. It's now a generally accepted fact that the modern dog traces back to a particular species of wolf, the Eurasian grey wolf (the similarities in appearance to dogs like the Husky are obvious, as can be seen with the above picture of my dog and the one of the grey to the left). The issues of where and when, however, are still disputed. Many geneticists argue that the original domestication of wolves occurred primarily in Southern East Asia, in the regions around and just South of the Yangtze river basin.

I'm no geneticist, but I've always found these arguments convincing, insofar as I am able to understand the data. They are based on the level of genetic diversity--along with specific genetic markers--being much higher among dogs in East Asia than in other parts of the world (note: appearance is not, in and of itself, indicative of diversity). Similar evidence--levels of genetic diversity--is used with regard to explaining the "races" of mankind by establishing the where and when of primitive man's initial exodus from Africa.

However, though the above theory continues to be dominant, it is not the only one being advanced. Recently, the idea of domestication occurring first--or at least independently--in Africa, not East Asia, has been gaining traction:
The team found genetic diversity among African village dogs is just as diverse as that of East Asian dogs, leading them to question the hypothesis of an East Asian origin for dog domestication.  
Dr Boyko told BBC News: "I think it means that the conclusion that was drawn before might have been premature. It's a consequence of having a lot of street dogs from East Asia that were sampled, compared to elsewhere. 
"The reason that East Asia looked more diverse than elsewhere was not because East Asia as a continent had more diverse dogs than elsewhere but because non breed street and village dogs are more diverse than breed dogs."
The issue of sampling strikes me as a fair one to raise and I can't help but notice a kind of researcher bias potentially also at play: Asian-based geneticists and researchers seem fixated on an Asian origin, African-based ones on an African origin, and European ones on an European origin. There is apparently a bit of pride in this regard, as unscientific as that may be.

The last--the theory that domestication occurred in Europe--is largely out of favor now, though. Genetic analysis does not support the hypothesis, though oddly enough archaeological evidence clearly does, as the first link above notes. But the author--in arguing for a Southeast Asian origin--then allows this is a result of geographical bias on the part of researchers focusing on Europe, which is exactly what those arguing for an African origin are saying about the Southeast Asia crowd.

It's a little comical, in some ways. But then it may very well point to a different truth also accepted by some researchers: domestication occurred in multiple places and at multiple times in history; there's no reason so suppose there was a single region--geographically speaking--that was primary in this regard. Of course, such diplomatic conclusions rarely pay the bills.

What all of the above theories tend to have in common, though, is the nature of domestication: it happened among people who were hunter-gatherers. Wolves--who are carnivores to be sure--found access to discarded scraps and bones around the camps of such people. From there, it is hypothesized that some were partly domesticated for use in guarding, hunting, and even as beasts of burden (this is exactly how the Husky was first used and is still used, by and large).

But a recent study--just published in Nature--calls the above narrative into question. The authors of the study argue that the key differentiating aspects of a domestic dog's DNA from that of a wolf are genes that allow the dog to better process and digest starches and sugars. Ultimately, modern dogs have come to rely on grains almost as much as proteins for a proper diet. What this means with reference to the evolution of the domestic dog is that such evolution would occur near human communities that were not hunter-gathering ones, but were instead settled agrarian ones. The earliest wolf-dogs simply adapted to the food source of these communities; evolution favored the genetic code better capable of processing starches and sugars, along with proteins.

This does not mean that the first domestic dogs appeared after the emergence of agrarian communities; far from it. What it does mean, though, is that at the very least there are multiple times and places for the evolutionary process of wolf to dog.

But personally, I'm struck by something else here, largely tangential to the question of how the domestic dog came to be: the role of diet with regard to fundamental natures. For there is one thing that is true, I think: the most heavily domesticated (and bred) breeds of dogs demonstrate the highest levels of a kind permanent adolescence, something that is theorized to be the basis of domestication in general.

For most domestic dogs never really change their day-to day behavior, as they move into adulthood. The ones that do are the serious working dogs still in use: various breeds used for shepherding and actual hunting (not just retrieving), along with those still used as beasts of burden. Like sled dogs. Anecdotally, I see this reality in my own two dogs. The older one--the mutt--is still looking to play, day in and day out. The younger, the Husky, expects to work, one way or the other.

Lacking something to pull, she has switched to outright protection. As I said, she is ready to kill any animal that enters our property. At night, I let her out into the yard and she sits motionless in the moonlight, waiting. She doesn't bark to scare things away or because another dog blocks away is barking. That's not work for her. She waits to kill, because much of her wolf-nature remains, because she is genetically closer to the wolf than is the other one, the mutt. Diet-wise, I suspect she would probably do fine on a more protein-heavy one.

So what about people? The expression "you are what you eat" is as old as the hills. But with regard to moving from a hunter-gatherer to an agrarian lifestyle, mankind's diet has changed in much the same way as the most domesticated dogs. Is it possible that our diets are slowly helping to establish a state of permanent adolescence, as well? Food for thought (pun intended).

Cheers, all.