Wednesday, October 3, 2007

Dogs and DNA

I saw two fascinating programs about dogs on Nature this week. If you have a chance to see them, I highly recommend them.

Dogs were domesticated in a very short time. The transition from wolf to dog happened possibly within one human lifetime about 15,000 years ago. And when I say 'from wolf to dog', I'm actually talking about physical changes to the animals' skeleton and teeth, as well as behavioral changes. This seems impossible according to classic Darwinian theory, although there is a lot of recent evidence that species can evolve very fast to adapt to changing enviornments.

For example, in the 1950's some Russians were trying to breed foxes for their fur. The problem was they were too wild to breed in captivity and had to be kept in separate cages. So a geneticist was brought in to try to create foxes that would breed in captivity. He decided to breed just the least aggressive foxes. He chose the foxes by putting a heavily gloved hand into the cage. The ones that just sniffed at it curiously were chosen to breed, the ones that responded aggressively were not.

In just 10 years, there was a completely different breed of animal. Their facial structure changed so they didn't have huge crushing jaws, their teeth shortened, even the coloration of their coats changed and they began to act like affectionate dogs. In fact, their skeletal changes were the same as those found in what's called the 'proto-dog', and kind of post-wolf, pre-dog breed as we know them, found in archaeological sites. The program showed films of the changed foxes, and of them wild and aggressive, then different looking and playing happily with children a few years later -- just a few dog generations later.

So now, there is a theory that what happened to domesticate dogs is this: About 15,000 years ago people began to live in permanent settlemens, the problem of garbage was created. When they moved around in a nomadic lifestyle, they just left the garbage behind and it disappeared before they returned, but once they were settled in one place, they had to have some kind of rubbish dump where they took bits of waste, the skeletons of animals they were done with etc.

These dumps would have attracted animals, including wolves. The wolves that stayed closest to the dumps had a better chance of survival, because they were simply closest to the food. It's called 'flight distance' - how far a creature flees when he feels endangered. Short flight distance = increased survival (in this case). Imagine the humans bringing out the remaining bits of carcasses and dumping them, and the wolves that stayed very near by were the most likely to get the food.

They didn't say this in the program, but I'm speculating that this would have been the marginal wolves, the young males who were without a pack, the lowest on the totem pole. The most desperate ones. The hungriest ones. Maybe even the loneliest ones, as they definitely like company. The strongest, the alphas, would have had other, better, resources for food and could afford to retreat farther.

Anyway, as demonstrated in the Russian experiments, when you select for curiosity and lack of aggression (which is pretty much the same thing as flight distance), you also select other genes inadvertently and thus, you can change very quickly the actual species itself.

Isn't that amazing?

The DNA part is that a Swedish geneticist is looking at the matrilineal DNA of dogs. He started out doing forensic work with dog hairs and that led to a huge international experiment of over 3000 dogs from all over the world. Basically, it looks like they all came from East Asia somewhere, maybe China. But that's still in progress.

And based on Bryan Sykes studies of patrilineal DNA in people, the story is incomplete without looking at that, too. So there will be more to come on that.

One more note is that dogs may actually have had a great impact on human civilization. There was some speculation about whether it would have been possible to domesticate other animals without dogs (dogs were the first domesticated animal). It showed border collies in a very hilly part of Cumbria herding sheep (2,000 sheep in 2,000 mostly vertical acres) in ways and in places that humans simply couldn't do. One of the scientists interviewed pointed out that herding is exactly like hunting, except that the dogs stop before killing. Since this is the kind of terrain that is the natural terrain of sheep and goats, man couldn't have herded them without dogs ever. He actually said that without dogs, it's possible we'd still be hunter gatherers. Though I think that overstated the case.

Whatever the case is, it's pretty remarkable to see working herding dogs at work -- the kinds of signals that they have to understand are very complex. things like -- hey you left one behind, and no, get that other group over there.

Also, the served an important protective function just as watch and guard dogs in early times, making villages more secure and secluded farms more secure. Changing the kinds of settlements people were safe in.

Finally they interviewes an interesting Inuit man, who said that without the dog his people would not have survived in the Arctic circle. They depend on them to find seal holes, protect them from Polar Bears (yes, they can get rid of bears), get them home in whiteout conditions when humans can't tell where they are. And to keep humans from falling through the ice. Dogs will stop short because they can sense in their feet the changes below the snow.

I watched the second show after I wrote this, and it was also fascinating. I'll just note one thing. Dogs are the most varied species in the world -- 500 different breeds recognized. And in the mid-19th century, there were only 40. The proliferation since then of pet dogs -- lap dogs -- has caused the variety.

So much I'm not saying from these fascinating programs, but this is already too long.

3 comments:

Kate said...

Sounds like a really fascinating program. If I knew how to turn on the TV, maybe I could also learn how to find the Nature channel. I would love to see it.

I love the DNA studies. Dogs seem to have originated in East Asia? That is fascinating.

That study you mention, the blue fox one, it took, iirc, 34 generations (30 or 40 years) to evolve through selection from savage beast to charming pet. The scientists involved, I have heard, were tasked with breeding animals that could be killed for their fur without savaging the executioners, but as the animals grew more petlike, their fur also became mottled, and less desireable as pelts. And the scientists fell in love with them and began to protect them.

I wonder why these have not become the fashion pet of the century. Can you imagine the market for a loving pet with soft, soft fur? It must be poor distribution--from scientists in Russia to pet lovers in NYC.

SybBrig said...

Just a word for the feline community -- all this talk of dogs makes me nervous and I must counterbalance.

There may be more breeds of dog, but cats communicate more. In a study I saw last spring (in the newspaper, so reliability is perhaps suspect) dogs have about 10 different howls/barks that they make (with different "intention", such as Feed Me, Stay Away, Puppy Where Are You, Mommy I'm Over Here), but cats have about 100 (if you count purring, too).

I can't attest to having heard more than 10 different sounds from the cats, and actually I can't find any indication of the discrepancy on the internet. But at least I've given equal air space to the felines as the canines.

The Bride said...

You need a TiVo, the best invention of recent years.

They don't know exactly where in East Asia, possibly China. The dogs were widely disseminated very rapidly after that. Possibly female dogs then inter-bred with local males as they moved Eastward around the globe.

The clue to the origin is that there is greater variety in the mDNA in East Asia. Just like 7 daughters of eve.

Buddhist monks intentionally bred the Pekinese, the 'lion look-alike dogs' a long long time ago for political reasons and at one time they could only be owned by the Emperor. Then when the Forbidden City was sacked at the end of the Boxer Rebellion, most of the dogs were slaughtered by the British, but 4 or 5 (those tender hearted Brits) were found alive amidst the rubble. One was taken back to Queen Victoria and that started the fad of lap dogs.

According to the tv show, the Russian experiment changed the dogs in 10 years not 30 or 40 -- which would have made it the 1990s, because it started in the 1950s. If foxes can breed at 6 months, as dogs can, that's nearly 20 generations in 10 years, though.

The problem as described on the program is that they wouldn't breed -- had to be kept in separate cages because they are essentially solitary animals, not pack animals. They wanted them to breed for fur for money, that's why they brought in the geneticist.

Yes, the fur wasn't so nice afterwards-- instead of pure black to silver blue, it had white spots on it. Actually they were really cute. You're right that it was a marketing failure.

Interesting that the fur gene is apparently linked to the aggression gene.

An other interesting thing is that the fashion in designer breeds -- cockapoos, labradoodles and maybe even Frenchies -- is seen by some as a really highly desirable fashion because many 'pure bred' dogs are just much too interbred, causing all the health problems and behavioural problems of some breeds

Was Bruce part Yorkshire Terrier and something else? What else, do you remember? He was bigger than the Chorkies. Maybe Jack Russell? Although they are famous for being aggressive.