Dog Emotion and Cognition will introduce you to the exciting new study of dog psychology, what the latest discoveries tell us about how dogs think and feel about us, and how we can use this new knowledge to further strengthen our relationship with our best friends.
Discovering Domestication, Part 2
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来自 Duke University 的课程
狗的情感与认知
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从本节课中
Evolutionary Accidents and Survival of the Friendliest
In this module, Dr. Hare explores three of his research studies he's done with foxes, New Guinea Singing Dogs, as well as research on wolves. He describes how early dog-wolves may actually be a product of natural selection rather than artificial selection, contrary to popular belief. He introduces a hypothesis called Survival of the Friendliest, which may explain how dogs, bonobos, and modern species evolved in contrast to close relatives, such as wolves and chimpanzees. Last, he relates the high level of social tolerance of these species to human by looking at human self-domestication.
与讲师见面
Brian HareAssociate Professor
Evolutionary Anthropology
Now all of those findings rely
on being able to compare the experimental population to the control population.
If Dmitry Belyaev had not, in the very beginning, the foresight
to have the control population, we wouldn't know if the selection for
friendliness and aggression actually caused the changes that we're seeing.
It could be that you see curly tails and floppy ears and
all these other things because the foxes lived in cages or
because where they lived or what they ate.
But we know because the control line was kept in absolutely identical conditions.
That it had to be the selection against aggression and interest that caused
the morphological changes, even though they were only selecting for behavior.
That's amazing.
So they also, when they measured the physiology of the experimental foxes.
They found that the serotonergic system had changed In the experimental line
versus control, the serotonin is actually higher in the experimental line.
And that is basically a way to sort of put a break on risky behavior or
aggressive behavior.
And the corticosteroid response to stress is much lower in the experimental line,
so your adrenal glands are on top of your kidneys, and they produce
things like cortisol which is associated with the fight or flight response.
And that was down regulated.
It was reduced in the experimental foxes, relative to the control.
So not only do you see morphological changes, but
you see physiological changes that are involved with aggression and stress, and
finally of course you saw a lot of behavioral changes.
But the neat thing is, the behavioral changes weren't just things that they have
selected for, like approaching and being friendly.
It was things like tail wagging and barking and crying into adulthood.
And so there's much higher levels of barking, and crying, and
tail wagging in the experimental line than in the control population.
And having worked with these foxes,
I can tell you that they are absolutely adorable.
Because when you see them, they cry and whine, and they really,
really want you to come touch them and interact with them.
Whereas the control line that has not been bread for this,
they tend to sort of stay away and not want to approach.
And they certainly don't bark and cry if you don't touch them.
So it's incredible that they selected for one thing.
They selected for interest in humans and
approach behavior, and you get all these changes.
This has huge impact on how we think about how evolution actually works.
Remember, evolution being a change in allele frequency over time, but
it It means that genes are busy.
They do multiple things, and the genes that must have changed in the population,
the allele frequency that changed in the population to cause a reduction and
aggression towards people, and also interest and approach towards people.
They also must be involved in producing the morphological traits and
the physiological traits that we see also change.
So there are accidental byproducts of selection against aggression
that tend to show up again and again, and that's what's suggested by the foxes.
Because it's obviously not just the foxes that have floppy ears.
It's all sorts of domesticated animals.
It's not just the foxes that have curly tales, or
piebald coats, or the star mutation.
And so really what the implications of the fox experiment is that
Dimitri Balaif had discovered what domestication is.
If you want to define it very quickly, domestication is selection against
aggression and it is selection for interest In people and
the willingness and even desire to be with people.
As a result,
you see all the changes that we see across lots of different domesticated animals.
So Dmitri Balayev really had solved a mystery, here.
For our question, though, the question of why is it that Dogs are so
good at using human gestures?
And our hypothesis that maybe it's something that occurred during
domestication, that those dogs that could really communicate better,
were at an advantage during domestication.
And that's why dogs are so good at using human gestures.
Well, this sets up the ultimate test, because the experimental population of
foxes, they are essentially domesticated, so what about them?
Are they gonna be really good at using human gestures since essentially
the experimental line looks so much like domesticated animals?
And then the second thing that was interesting is, there was no selection by
the Russian scientist on the communicative ability of these foxes.
They weren't playing the gesture game.
They weren't playing communicative intention games with the foxes over
the 50 years.
In fact, none of those games had even been invented.
When Dmitri Belyaev began doing these studies.
So, clearly the foxes hadn't been selected to do this.
They had only been selected for interest in people.
So our question was, if it really was domestication that has made dogs so
remarkable using gestures, what will the foxes do?
And what we found when we went and played our game and we hid food in one of two
places, and you can see my collaborator pointing to one cup over another, and
we compared fox kits from the experimental line and the control line.
And what we saw was that
the experimental line was really good at using the human gestures.
And the control line was not so good.
Now the important thing that we did hear is we actually spent a lot of
time getting the control pups who are really young and
didn't quite have their adult fear system online yet.
We spent a lot of time playing with them, practicing them,
having them make choices to get them ready.
We actually spent five weeks exposing them to people.
Sort of socializing them.
Where as the experimental fox kits,
when it was time to play the test game with them, we literally just went and
got them from their home cage and we went and played the games with them.
And they had almost no exposure to people relative to the control kits.
So, even the control kits had much more exposure to people, what we see is
the experimental population they actually, this is a comparison to dog puppies,
the 18 repetitions we gave them got right about 15 times when we pointed.
Where as dog puppies were about at that same level, but
when we look at the control line,
the control line was significantly below the performance of the experimental line.
Now the interesting thing is that the control line did use the human cues,
just at a lower level.
So that five weeks of exposure actually helped the foxes
that were in the control line.
Sort of get used to humans and show some proficiency.
And that's really interesting when we think about the origin of the ability
of dogs, or in this case the experimental foxes, to use human gestures.
It's not that it's probably not the case.
That the dogs just have a completely new ability to use gestures.
It's probably that wolves, or
in the case of the control foxes, that if you give them a lot of socialization and
you give them a significant amount of practice, they can use gestures, too.
And it's that ability that then when you domesticate
an animal then increases and becomes even more extreme and allows for
the remarkable skill we see in dogs and, of course, in the experimental foxes here.
Now I wasn't convinced yet.
I wanted to make sure that we measured this in a couple ways, because it was so
interesting and important for
understanding the origin of dogs' remarkable abilities.
