Not the Discovery Channel

What we really know about the past

Human and Dog co-evolution

One of the great disappointments in my life is that I’m allergic to dogs. I love dogs, always have. So much so that I’m willing to put up with my allergies to interact with them as much as possible.  My favourite breed is an Australian Blue Healer. We had them on the farm where I worked in Belize and they were amazing. Easy to train, incredibly smart, playful, and loyal. They were also working dogs, with jobs to do. They seemed to know their jobs well and (for example) wouldn’t let you go riding off into the jungle by yourself-unless you were in a car, they didn’t really seem to care if you left in a car.

I loved those dogs. I haven’t been able to have one of my own, as my life tends towards the unstable and I don’t think it would be fair to the dog. I also tend to like the bigger breeds and they need a lot more room than I can currently offer. If I’m honest guess it’s not really the big breads I like, rather it’s breeds that started off as working dogs. I don’t get along so well with Companion Dogs. I guess it’s because my only real experience has been with Working Dogs and we tend to communicate better. Recently I have been introduced to a great Pitbull. Playing with him got me thinking about dogs. And because I’m an archaeology geek, it got me thinking about the first dog.

This is all a by way of introducing the topic of the domestication of dogs- a very interesting story.

I’m not going to get side tracked by other domestication events (I’ll write about cats later), or different breeds of dogs. Like how the bulldog was bread to kill or subdue bulls by biting their nose. Nope, not going to go off on a tangent and talk about how some people claim that the wrinkles helped channel the blood away from the eyes, while the mushed face allowed it to breath better while holding on with its teeth, or how the small hind-end also stopped it from breaking its spine while being thrashed around by the bull. I’m definitely not going to talk about how that’s not really the reason they look like they do now. With the Cruelty to Animals Act of 1835, bull-baiting was essentially finished, and bulldogs began to be promoted as pets, eventually being crossed with the pug to give them the short-faced wrinkly look common today. The older English bull-dogs looked more like an Alaunt, or Mastiff, but with greyhound mixed in. The greyhound mix was to make them faster, to help with the bull fighting. Nope. Not going to mention that.

A Bulldog from the 18th century. Less wrinkles, more bull fighting

 

A modern bulldog. Less bull fighting, more wrinkles

But enough about things I’m not going to talk about- things that are so fascinating to me that I could go on and on and on. Instead lets look at the actual origin of the domestic dog. I’m not going to spend too much time on the evolution of the canine linage , except maybe pointing out they share an order with bears, skunks, raccoons, seals and a bunch of other predators. Also the common ancestor of dogs and cats was the Miacidae, a line that died of about 35 million years ago- but not before creating new lineages that resulted in almost everything that can eat your head now a days. They were also called hypercarnivors, which isn’t as cool as it sounds. Like the Camel and Horse, the earliest canines evolved in North America, crossing the Bering land-bridge to spread out across the world.

Dogs, Wolves, Coyotes, and Jackals are all subspecies of Canis lupus. Dogs are domesticated versions of C.Lupus, while Coyotes and Jackals are sub-species that are basically too small to earn the name wolf.  There are also many other (now-extinct) sub-species of C.lupus, like the Dire Wolf– a species that died off with most of the other Pleistocene Megafuana about 10,000 or so years back. Other animals that went with the Dire Wolf into the annals of the fossil record were the Sabre-toothed cat, the American Cave Lion, a 200 pound Giant Beaver, and my person favourite, the Short-Faced Bear.

They were all very interested in shadows

The origin of the domesticated dog is still hotly contested by researchers. Though it is (fairly) well established that dogs were bread from Eurasian wolves, exactly where, when, and how is still up for debate. Dealing with each of those questions in order, here is what we know about our relationship with Canis lupus familiaris.

First the where question. One study on the DNA of wolves and dogs suggests that dogs went through four different domestication events, while another study suggests that modern dogs all share a common gene pool from a single East Asian population. Yet another study, this one from 2009, argues that all dogs descended from at least 51 female wolves located along the Yangtze River in China.  A much larger, and more recent study suggests that the genetic origin for modern dogs is in the Middle East, with inter-breading with local wolves populations occurring after  initial domestication and muddying up the gene pool. Getting at history through genetics is often difficult because of that kind of thing, but morphological data suggests an Middle Eastern or South Asian origin, so that backs up the last two theories.

The when is another complex story. The study that suggested the Yangtze river as an origin place for the domestic dog also suggests a date of less than 16, 300 years ago for the time, but that date has some problems. Early evidence of dogs have been dated to 31,700 years ago from sites in Eastern Europe. The remains from these caves look more dog-like than even modern wolves, though there is nothing in the data that points directly to dog-human interaction, so it is far from conclusive. Early humans may have interacted with wolves, perhaps unintentionally, or wolves may have become more dog-like as part of a natural adaptation to human behaviours.

The problem is that early canines and early humans shared a similar niche and its sometimes really hard to tell the difference between actual interaction and just crossing paths with each other.  Take Chauvet Cave in France as an example. The cave is littered with wolf, bear, and human footprints- all crossing each other. I doubt that this was some Scooby Doo inspired chase involving wolves and bears. That would be awesome, but it’s much more likely that different animals used the cave at different times. On the other hand, a set of small human footprints were found side-by-side with canine footprints. These prints had a shortened middle toe, a characteristic of dogs not wolves. Carbon dates from soot left by the child’s torch dates to around 26,000 years ago. Though I love the idea of some pre-historic cave Lassie and little Timmy exploring, it’s not exactly conclusive evidence.

It does let me use this picture though

Conclusive archaeological evidence of dogs interacting directly with humans doesn’t really appear until much later. In 1978 Israeli archaeologists found the bones of a clearly domesticated dog in a 12,000 year old grave. Another site in Germany has burials contain both dogs and humans.  The newest archaeological evidence was reported in July of last year. Researchers working at the Kesslerloch Cave in Switzerland found teeth and skull fragments from domesticated dogs in layers in the cave dated to 14,000 years ago. Although the very early dates (30,000 years ago) are somewhat suspect, we have definitely been interacting quite closely with dogs for quite some time now, living and dying with them for at least 14,000 years.

So then, a recap: We don’t know exactly where the first dogs were domesticated, but it was likely either southern China and/or the Middle East. We also don’t know when, but we’re pretty darn sure it happened before 14 thousand years ago, maybe even as far back as 30 thousand. And now, the how. I like the how questions, mainly because they tend towards the more confusing. And confusing is good. Almost nothing that happens is simple.

The wikipeadia article on dog domestication breaks down the various different explanations of  dog domestication quite well.So I’m going to copy their style and give you three different explanations. But with my less-than-scientific names for them. You know, because I think I’m clever.

1. The ‘awwww’ explanation

Basically this idea is that humans may have started interacting with wolves via the adoption of orphaned wolf cubs. These adopted cubs would have begun to socialized with humans, changing their behaviour and eventually breeding a new population. The key point to this is that the cubs had to be taken really early in life, either after the mother had been killed by a human hunter, or orphaned by some other means.

It’s not too far-fetched an idea. Humans have a disposition to want to care for cute things. Way back in the late 1940s a German zoologist named Konrad Lorenz suggested that animals with infant like features evoke a nurturing response in humans. Heck some studies suggest we even respond better to human babies we think are cuter. We also react quite favourably to animals who exhibit pedomorphosis (keeping a cute appearance even after reaching adulthood). we don’t just do this with our pets, almost all our domesticated animals have this in some way- we even do it with things we’re going to eat, like chickens and cows.  There may also be some instinctual response to the noises pups make, but I can’t find anything concrete about that.

We also tend to associate things we find cute with innocence. Stephan Jay Gould wrote about the increasingly infant-like appearance of Mickey Mouse as his character changed  from mischievous to innocent. So we may not see a cute wolf pup as anything other than innocent and in need of our care. Surly it would never bit our face off. It’s too cute.

awwwwwwwwww

Its not unreasonable to assume that after running into those guys in that picture, some people might pick them up and take them home. Domesticating them would not be easy however.We have a whole bunch of data on this. Apparently there are between 30,000 and 2,000,000 privately owned wolves in the U.S alone. Though I don’t know how wikipeadia got that number and I couldn’t find another source.

Wolf pups are very hard to socialize, especially after 3 weeks or so. Some studies suggest that if you don’t get them before they open their eyes (day 10) then you will have an even harder time. They also socialize differently than dog. For start they apparently only socialize to humans in the absence of any adult wolves. They also have a strong independent streak and will suddenly decide not to listen to commands. Wolves apparently respond better to hand signals that vocal ones, making it hard to direct them in a hunt.  Not saying it’s impossible to train a wolf, but its hard. On the other hand us humans do tend to form strong attachment to things we think of as ‘pets’ and that might be all the motivation we needed. They would also be useful animals to have around. The could help guard camps, hunt, and keep you warm at night. Which leads us into our second theory.

2. It wasn’t intentional

This particular theory suggests a process of ‘self-domestication‘. Proposed by Raymond Coppinger, this theory suggests that it was the wolves themselves that were responsible. This theory suggests that as humans began living together in larger groups, we created more opportunities for wolves to scavenge from us. This new food source (our leftovers) created a new ecological niche- one that favoured wolves with reduced flight distances. Flight distance is science-speak for how close an animal will let you get before they run away.

Yup, that's an accurate image of that idea

This meant that certain wolves, who were more adventurous (see last weeks post) got more food with less effort. These “village-oriented canids” would have self-selected for less freighted, friendlier behaviours. Essentially they would have tamed themselves.

Experiments with silver foxes, going on for the last 60 years (!) show that when selecting for ‘tame’ behaviours, the foxes simultaneously changed in appearance, retaining their puppy features longer and generally becoming more dog-like in their appearance.  They also changed their other behaviours, increasing the amount of whining, barking and submissiveness. So, if the ecological factors favoured a more tame wolf, its possible that wolves started to become dogs without our help at all. But why keep them around? I have mentioned hunting and guard duty already. Was this enough to put up with essentially wild animals at our doorstep?

3. Dogs get all the crap jobs

Basically the last two theories on the wikipedia page can be combined into one. These theories suggest that dogs were domesticated for fur, or for food, or as beasts of burden. I’ll be quick on these ones, because they are pretty self-explanatory.

it's also been awhile since we had a picture of a puppy

Taking the three points in reverse order; the beast of burden explanation makes a great deal of sense. Think about Huskies and Dog-sleds. It has even been suggested that dogs played a part in bringing humans to the New Wold. The Blackfoot people of Alberta also divide their history in two parts, the first being the time when dogs were used as beasts of burden, and latter when they switched to using horses (horses being re-introduced into North America by Europeans).

Dogs as food is a trickery topic, because we have such strong cultural taboos against it- but that’s not universal. It definitely shouldn’t be ruled out as a possibility. Dogs for fur is also not uncommon. Here on the Northwest Coast for example, dog-hair was used to make clothing and blankets. The Salish Wool Dog was bread for exactly that purpose– it was even sheared like you would a sheep.  The original Cowichan Sweater was made of dog wool. If you don’t know what that is, it’s alright I don’t blame you (much), but they’re famous on the Coast. People love them. Some people even dress their dogs in them.

oh sweet irony!

Okay, so that was the basic where, when, and how of our domesticated friends. No word yet on the role that tennis balls played in the domestication of dogs.

One final note- because I can’t help but get a little meta on y’all.

Those three explanations about the process of domestication are not exactly exclusive. We know wolf puppies are hard to train, and unpredictable even after you train them. A wolf could obey a command many, many times, and then suddenly decide to ignore it. (I know some dogs that have selective hearing as well. And people.)

It is more prevalent in wolves though. So maybe just grabbing random abandoned wolf pups might not be the smartest idea. However, if the pups you were grabbing were part of a line of wolves that had started to adapt to human presence already, then maybe training them would be so hard.

In this scenario (which is purely hypothetical) these less cautious wolves still have pups that are incredibly cute, but don’t have the genetic disposition to socialize exclusively with other wolves. Human’s start interacting more and more with- or even adopting the orphans of- these more dog-like, but still wild wolves (think about the 30,000 year old part-wolf, part-dog skull mentioned above). This interaction proves fruitful for both human and friendly wolf. Humans hang out with dogs more and more, realizing their usefulness for hunting, safety, companionship, even food and clothing. Eventually this relationship results in the creation of a brand new species-Canis lupus familiaris.

This speciation also results in wolves that have an increased cautionary behaviour to humans, since the split removed those with shorter flight distances from the wolf gene pool. They likely would also have to stay further away now that dogs are around eating all the left-overs. And Barking.  If this is the case, our experiments on captive wolves are skewed towards less trainable individuals than early wolves.

See now, not every theory has to compete with each other. We can all get along. That hypothetical combination also happens to satisfy one of my base-line observations on human culture- we rarely do anything for a single reason. I suspect dogs are similar.

Okay. One more picture of a cute dog. How about one of the dog that started this post?

awwwwww

Thanks to Mel for the picture. And letting me play with him.

 

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UPDATE– feb 15th, 2011

I just saw a blog post over at the Genealogy of Religion, which brought a new article to my attention. Not sure why I didn’t see it before I posted this, but let me correct the error. The article refers to Middle Epipaleolithic burials dating to between 13,5000- 12,500 years ago (aprox). The authors make a good argument for a spiritual/emotional connection between these early people and foxes, suggesting a similar relationship as early wolves and humans (read: flight distances above). Though you should remember that foxes were not domesticates, there presence in the grave does demonstrate a close human-canine interaction. Not the one that lead to Dogs, but maybe a simillar behavioural case?  It will be interesting to see what comes of this.

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