Wolves were domesticated twice

How did wolves turn into dogs? Humans and wolves have been interacting together for as long as both species have been on the planet, but the first evidence of dog-like characteristics appearing is about 15,000 years ago. But what caused this? Well, just last month a study uncovered a revelation about this domestication - it happened more than once! I spoke to Greger Larson from Oxford University to see what he had dug up...

Greger - The first big thing that we've just discovered is by sequencing a genome of a 4,800 year old dog from Ireland. From that we were then able to compare that very conclusively to all the modern genomes that have been sequenced and that then, through the analysis, through the phylogenetic trees and molecular clocks, and looking at the pattern of different genetic signatures in time and space made us think that perhaps dogs were domesticated not once as being previously suspected by a lot of geneticists, but twice.

Georgia - What are the implications of this domestication happening twice?

Greger - Well if it's happened twice that makes it go from being something like an accident - I mean anything can happen once. But as soon as it twice on several thousand miles, several thousand kilometers apart from each other, it seems like maybe it sort of lends an inevitability to this that makes it seem like there was a set of environmental circumstances that was the same over a very wide range wherein people and wolves started interacting in a way that they hadn't done for the last 150,000 years prior to that. And that interaction, and that sort of romantic dance, as it were, between the wolf population and the human population getting used to one another and partnering up in a way that they hadn't done before that led to what we now know as domestic dogs.

Georgia - Do we know about how this came about?

Greger - We don't really. What we can guess from looking at comparisons and using analogues from the rest of the natural world. So, one hypothesis that we've been talking about recently is this idea that there were potentially different wolf ecomorphs, and by that I mean different populations of wolves that were specialising based upon the kind of they that they were going after. In the same way that there are killer whales off the northwest coast of North America, some pods go after salmon, some pods go after seals, and they don't really like each other, they don't really talk to each other. When calves are born they're raised in either seal eating or salmon eating and they kind of know that the other killer whales are out there but they don't really talk to them that much, and we know that wolves are very capable of this. There are very well known wolves that are on the TV every week that hunt caribou, but there's other wolf populations that don't go anywhere near the caribou and subsist of completely different resources in forested environments.

So what we suspect might be happening is that about 15,000, maybe a few thousand years before that, maybe two independent wolf populations started following people rather than following anything else, or rather than trying to get resources in any other means, and getting used to that human niche. And in doing so would start to protect that human niche and that would initiate reduction in the gene flow between that wolf population and wolf populations that were doing other things. That may have activated this process of domestication very early on which wouldn't require any initiation from people who were acting intentionally in goal directed fashion to try and generate a chihuahua puppy from a wild wolf, which of course they couldn't have known about because there were no domestic animals.

Georgia - So while one group of wolves made its living from following humans, others did not and the two groups wouldn't have interbred so started to change. The wolves who hung around humans need different characteristics t do well: having low fear and low aggression. And, over time, this relationship became more and more entrenched and people started selecting which dogs would live and which would die, and selecting for tameness also changed the wolves in other ways...

Greger - There was an experiment in the '50s in Siberia, where they were just selecting for foxes solely on the basis of how a lack of fear and a lack of aggression that the demonstrated when someone put a hand into a cage. And they only selected those animals that had the least amount of fear, or the most curious, and the most friendly and within a couple of dozen generations, those foxes started looking like a lot of the characteristics that domestic dogs have. They started getting smaller overall, they had differences in their shapes, and their coat colours, and their snouts, and they started barking. So it was a very clear demonstration that simply by selecting for a tame behaviour you can get all of these changes that we recognise as what we call the domestication syndrome.

Georgia - And so wolves started to become dogs. But why did humans tolerate these animals being around in the first place?

Greger - You are much better able to exact resources and to get calories out of an environment when you've got a wolf partner. And here are many instances where from Japan to Southern Scandinavia to even the southeast corner of the U.S in the mesolithic, prior to the advent of agriculture or at least prior to agriculture arriving in those areas, where people are burying their dogs with more grave goods than they're burying with a lot of people. I mean seriously, these dogs are being revered as very hugely important members of society - as equals, or in some cases even better than some of the people.

So there was a clear partnership there and you would only do that if those dogs were very important to your well being in those environments . There's lots of speculation about how they were used in hunting and clearly they have much better olfactory capabilities than we do.  And if you were able to cut an animal with a microblade on a long stick and then the animal runs, it's hard for us to find if it runs in a dense forest but dogs have an amazing sense of smell and would be able track them down and that would lead the humans to them and boom... you've got dinner!

Georgia - Man's best friend indeed! And dog's were the very first domestication in human history. It was the start of a trend which led to life as we know it.

Greger - So until you have domestication you certainly don't have the capability of humans expanding their population sizes to afford the kinds of technological advances that we've seen over the last 10,000 years.