> Domestication shaped wolves into dogs and transformed both their behavior and their anatomy. Here we show that, in only 33,000 y, domestication transformed the facial muscle anatomy of dogs specifically for facial communication with humans. Based on dissections of dog and wolf heads, we show that the levator anguli oculi medialis, a muscle responsible for raising the inner eyebrow intensely, is uniformly present in dogs but not in wolves. Behavioral data, collected from dogs and wolves, show that dogs produce the eyebrow movement significantly more often and with higher intensity than wolves do, with highest-intensity movements produced exclusively by dogs. Interestingly, this movement increases paedomorphism and resembles an expression that humans produce when sad, so its production in dogs may trigger a nurturing response in humans. We hypothesize that dogs with expressive eyebrows had a selection advantage and that “puppy dog eyes” are the result of selection based on humans’ preferences.
Perhaps relatedly, you can often see the sclerae of dog eyes, which you can't with wolf eyes. I think there was selection pressure there too: it was evolutionarily advantageous for a humans to be able to signal to each other where they were looking without speech or a gesture, and the same is probably true of, say, canine hunting companions.
I can't really back this up, but it's something I've noticed.
That’s an interesting idea for why you can see the human sclera! (And so clearly as well — its one of the defining features of the human face, except in Anime). It otherwise seems like an evolutionary disadvantage.
What I like about your surmise is that, AFAIK, canis familiaris is the only animal other than the great apes that understand gestural ostention (if you point at something a cat will look at your finger while a dog will look at the thing you Re pointing at). As a pack-hunting animal this silent communication is pretty important for dogs and you can see how it could have adapted to humans.
I just did a quick search and there is a recent paper alleging that house cats have some ability to recognize gaze but not gesture, which also suggests this mechanism might be at work.
I forget where I read this but apparently dogs have evolved to understand human body language as well.
For example, if a dog goes into a room with a stranger and the stranger then points to one of several buckets, the dog will generally go over to that bucket. This is without any prior training or experience to pointing on the dog's part.
This apparently doesn't work with children so the theory was that over time, the dogs that responded best to human body language were more likely to survive due to getting more treats etc.
Our neighbour had a golden retriever who I would feed the odd treat to (because who doesn't like dogs?). One day he saw me and came up to me and looked at my face to see if I was looking at him, and then with his eyebrows gestured to my pocket (where I normally kept treats for him) and then looked at my face again.
Yeah dogs get really good at a few things, especially when it comes to food. They are really good manipulators too, generally to get food.
My dog only needs to be given a treat once by a shop owner and every walk afterwards he’ll go up to the door of that shop.
I took him with me to pick up a framed picture once and the shop owner had a few treats for him. We don’t often go by this shop and this was awhile ago. And now when do walk past he pulls a bit to suggest we go inside.
Or if they find some food under a bush or something - they’ll check quite a few times later to see if it magically restocked.
They also try things out to see if it works in getting them food. Which is why it’s important to not fall for their tricks. Easier said than done as they know how to use their facial expressions to get what they want.
When it comes down to it, dogs simply have a lot of time on their hands. They get good at figuring out which sounds and actions mean what at certain times. And they figure out how to manipulate that. Almost like inmates that have nothing to do all day but think up schemes.
I unfortunately know more than I would like about dog eyes, because my 4 year old GSD had cataracts. Some of the differences the vet told me are interesting.
Dogs vision is about 20/200 in general, and they can only use their lens to focus 1-2 diopters (compared to about 6 for people).
Dogs can track movement and see in low light better than we can. The way that he did an eye test was simply to drop a cotton ball, the difference before surgery and 2 days after surgery was stark. He would ignore it before, and afterwards his head followed it.
> Dogs can track movement and see in low light better than we can.
This goes against my experience. When I was dog sitting my mother's dog a few years ago and we were going for the final walk of the night, she'd regularly get surprised by people passing us from the opposite direction. She'd notice them 1-2 meters away and would jump back and bark, while I was easily able to see them 5-10m away. I've had similar experiences with another dog.
Would they notice them better if they were moving side to side instead of slowly becoming bigger while walking towards us?
I'd be careful with this one. I thought the same when I got a puppy, I'd heard similar repeated (often 20/75 is mentioned as well), and especially that they're not supposed to see well in the dark. After his adolescence my Texas Heeler seems to have excellent vision. He regularly spots small birds, piglets, humans, etc at a distance of 1/4 mile through our window (that's as far as the view goes, but many of the objects he sees rival in size what a human can see at a similar distance). Nighttime does not seem to effect this much. I'm sure his vision is at least 20/40, probably even better than 20/30.
He also seems to have more aggressive pattern recognition through partially obscured sightlines. e.g. seeing a deer or human from just a tiny visual sample viewable through dense trees/brush. However, while this seems to have higher sensitivity than humans (sees the deer when humans dont) it also seems to have somewhat lower specificity (occasionally he thinks something is there when it really isn't).
While this could be due to some Dingo genetics not found in other dogs (unique to Australian Cattle Dogs), it's worth noting that Icelandic Sheepdogs were bred partly to defend unusually small icelandic sheep/goats from unusually large birds of prey that eat them (the white-tailed eagle). Therefore they bark at everything that flies, and some owners have noted that they sometimes bark at birds or airplanes that are quite difficult for humans to see.
My personal hypothesis is that there is wider individual variation in canine sight acuity than is acknowledged by the typical rules of thumb.
I use that fact quite a bit when training my labrador; when in the woods, if she ranges too far, I'll just stop and stay completely motionless. She'll fail to see me at about 15-20 meters from me, especially if I'm against a tree or something. Even if I'm not obscured at all.
Soon tho, her nose will pick me and I can then see her eyes 'click' on me eventually. I use that trick to keep her "worried" she'll lose me, so she keeps checking on me at shorter intervals and control her urge to follow a yummy smell.
The interesting thing is that on the other hand, she has no problem tracking a moving object in flight at 100m, like a pigeon. Once I was shooting clay pigeons, and missed one overhead, and a few minutes later she came back all happy with my unbroken clay target, she had tracked it, marked it, and retreived it!
I wonder if perhaps in addition to bigger eyes being cuter and therefore preferable, we're able to form bonds with animals more easily as a result of larger eyes- or perhaps more broadly that large eyes can be advantageous for social bonding. Dogs and their owners engaging in mutual gazing causes similar Oxycontin release to mother-infant gazing. I think ideas like the eyes being a "window into the soul" are related, and we're more likely to be able to determine if someone is trustworthy and genuine as indicators like pupil size are involuntary.
Humans have had a very large hand in this evolution.
Dogs are probably the most heavily bred animal in the last 300-400 years. Many (most?) breeds of dogs only exist because humans specifically bred for certain traits.
When breeding for behavioral traits, a dog with expressive eyes who can make humans feel a connection has gotta be a winner over ol wolf eyes over there.
While I agree with your general point, I think livestock is more heavily bred. Chicken, cows, poultry and pigs that "live" in factory farms nowadays can't even survive out in the wild, nor do they have particularly long life-spans.
Reminds me of the Russian experiment that worked to prove that a selection process for behavior could produce domesticated foxes. An unanticipated side effect of the experiment after six or seven generations was that the foxes facial phenotype began to resemble dogs:
I don't know if this is true but I've heard that at fox farms they kill the aggressive foxes. Resulting in the foxes getting more and more tame. So they are basically killing dogs for their furs.
There has definitely been experimentation on the domestication of foxes, and if I recall correctly they would sell the foxes furs when funding ran dry. Though I don't know to what extent this applies to commercial fur farms. I actually was not even aware that fox fur farms are a thing.
U know what is cool, human eye's sclera is white making it easier to know where a person is looking and to trust them. As opposed to gorillas you never know if they eying u to maul ur head.
A small percentage of gorillas do have a human like white sclera. Linked article includes pictures.
> Out of the 60 western lowland gorillas they considered, only 30% had completely dark scleras. The remaining 70% had some degree of white in their eyes. Of these, a small sample of 7% had all white, human-like sclera.
I started reading this expecting it to be about dogs' optics but instead it's all about them having developed the ability to use their eyebrows for human-style emotional expression.
[+] [-] EndXA|5 years ago|reply
Abstract:
> Domestication shaped wolves into dogs and transformed both their behavior and their anatomy. Here we show that, in only 33,000 y, domestication transformed the facial muscle anatomy of dogs specifically for facial communication with humans. Based on dissections of dog and wolf heads, we show that the levator anguli oculi medialis, a muscle responsible for raising the inner eyebrow intensely, is uniformly present in dogs but not in wolves. Behavioral data, collected from dogs and wolves, show that dogs produce the eyebrow movement significantly more often and with higher intensity than wolves do, with highest-intensity movements produced exclusively by dogs. Interestingly, this movement increases paedomorphism and resembles an expression that humans produce when sad, so its production in dogs may trigger a nurturing response in humans. We hypothesize that dogs with expressive eyebrows had a selection advantage and that “puppy dog eyes” are the result of selection based on humans’ preferences.
[+] [-] archi42|5 years ago|reply
[+] [-] bitwize|5 years ago|reply
I can't really back this up, but it's something I've noticed.
[+] [-] gumby|5 years ago|reply
What I like about your surmise is that, AFAIK, canis familiaris is the only animal other than the great apes that understand gestural ostention (if you point at something a cat will look at your finger while a dog will look at the thing you Re pointing at). As a pack-hunting animal this silent communication is pretty important for dogs and you can see how it could have adapted to humans.
I just did a quick search and there is a recent paper alleging that house cats have some ability to recognize gaze but not gesture, which also suggests this mechanism might be at work.
[+] [-] alexpotato|5 years ago|reply
For example, if a dog goes into a room with a stranger and the stranger then points to one of several buckets, the dog will generally go over to that bucket. This is without any prior training or experience to pointing on the dog's part.
This apparently doesn't work with children so the theory was that over time, the dogs that responded best to human body language were more likely to survive due to getting more treats etc.
[+] [-] gadders|5 years ago|reply
Smart dog.
[+] [-] nemo44x|5 years ago|reply
My dog only needs to be given a treat once by a shop owner and every walk afterwards he’ll go up to the door of that shop.
I took him with me to pick up a framed picture once and the shop owner had a few treats for him. We don’t often go by this shop and this was awhile ago. And now when do walk past he pulls a bit to suggest we go inside.
Or if they find some food under a bush or something - they’ll check quite a few times later to see if it magically restocked.
They also try things out to see if it works in getting them food. Which is why it’s important to not fall for their tricks. Easier said than done as they know how to use their facial expressions to get what they want.
When it comes down to it, dogs simply have a lot of time on their hands. They get good at figuring out which sounds and actions mean what at certain times. And they figure out how to manipulate that. Almost like inmates that have nothing to do all day but think up schemes.
They’ll get away with whatever they can.
[+] [-] cpwright|5 years ago|reply
Dogs vision is about 20/200 in general, and they can only use their lens to focus 1-2 diopters (compared to about 6 for people).
Dogs can track movement and see in low light better than we can. The way that he did an eye test was simply to drop a cotton ball, the difference before surgery and 2 days after surgery was stark. He would ignore it before, and afterwards his head followed it.
[+] [-] luckylion|5 years ago|reply
This goes against my experience. When I was dog sitting my mother's dog a few years ago and we were going for the final walk of the night, she'd regularly get surprised by people passing us from the opposite direction. She'd notice them 1-2 meters away and would jump back and bark, while I was easily able to see them 5-10m away. I've had similar experiences with another dog.
Would they notice them better if they were moving side to side instead of slowly becoming bigger while walking towards us?
[+] [-] rckoepke|5 years ago|reply
I'd be careful with this one. I thought the same when I got a puppy, I'd heard similar repeated (often 20/75 is mentioned as well), and especially that they're not supposed to see well in the dark. After his adolescence my Texas Heeler seems to have excellent vision. He regularly spots small birds, piglets, humans, etc at a distance of 1/4 mile through our window (that's as far as the view goes, but many of the objects he sees rival in size what a human can see at a similar distance). Nighttime does not seem to effect this much. I'm sure his vision is at least 20/40, probably even better than 20/30.
He also seems to have more aggressive pattern recognition through partially obscured sightlines. e.g. seeing a deer or human from just a tiny visual sample viewable through dense trees/brush. However, while this seems to have higher sensitivity than humans (sees the deer when humans dont) it also seems to have somewhat lower specificity (occasionally he thinks something is there when it really isn't).
While this could be due to some Dingo genetics not found in other dogs (unique to Australian Cattle Dogs), it's worth noting that Icelandic Sheepdogs were bred partly to defend unusually small icelandic sheep/goats from unusually large birds of prey that eat them (the white-tailed eagle). Therefore they bark at everything that flies, and some owners have noted that they sometimes bark at birds or airplanes that are quite difficult for humans to see.
My personal hypothesis is that there is wider individual variation in canine sight acuity than is acknowledged by the typical rules of thumb.
[+] [-] buserror|5 years ago|reply
Soon tho, her nose will pick me and I can then see her eyes 'click' on me eventually. I use that trick to keep her "worried" she'll lose me, so she keeps checking on me at shorter intervals and control her urge to follow a yummy smell.
The interesting thing is that on the other hand, she has no problem tracking a moving object in flight at 100m, like a pigeon. Once I was shooting clay pigeons, and missed one overhead, and a few minutes later she came back all happy with my unbroken clay target, she had tracked it, marked it, and retreived it!
[+] [-] AdmiralAsshat|5 years ago|reply
https://en.wikipedia.org/wiki/Neoteny#In_domestic_animals
We breed animals for bigger eyes and other features to make them cuter--to make them look more like babies.
[+] [-] kipchak|5 years ago|reply
https://www.scientificamerican.com/article/is-the-gaze-from-...
[+] [-] war1025|5 years ago|reply
[1] https://en.wikipedia.org/wiki/Neoteny_in_humans
[+] [-] annamargot|5 years ago|reply
Dogs are probably the most heavily bred animal in the last 300-400 years. Many (most?) breeds of dogs only exist because humans specifically bred for certain traits.
When breeding for behavioral traits, a dog with expressive eyes who can make humans feel a connection has gotta be a winner over ol wolf eyes over there.
[+] [-] teraku|5 years ago|reply
[+] [-] kingkawn|5 years ago|reply
https://en.wikipedia.org/wiki/Domesticated_red_fox
https://en.wikipedia.org/wiki/Dmitry_Belyayev_(zoologist)#Be...
[+] [-] tsdlts|5 years ago|reply
[+] [-] kipchak|5 years ago|reply
[+] [-] z3t4|5 years ago|reply
[+] [-] throwawayffffas|5 years ago|reply
See https://en.wikipedia.org/wiki/Domesticated_red_fox#Experimen...
[+] [-] akeck|5 years ago|reply
[+] [-] wrnr|5 years ago|reply
[+] [-] lowdose|5 years ago|reply
> Out of the 60 western lowland gorillas they considered, only 30% had completely dark scleras. The remaining 70% had some degree of white in their eyes. Of these, a small sample of 7% had all white, human-like sclera.
http://www.bbc.com/earth/story/20150808-gorillas-with-human-...
[+] [-] wrnr|5 years ago|reply
[+] [-] mrlonglong|5 years ago|reply
[+] [-] taneq|5 years ago|reply