Dogs' Eyes Have Changed Since Humans Befriended Them (2019)(theatlantic.com)
theatlantic.com
Dogs' Eyes Have Changed Since Humans Befriended Them (2019)
https://www.theatlantic.com/science/archive/2019/06/domestication-gave-dogs-two-new-eye-muscles/591868/
43 comments
Was already posted in 2019 (251 points), but afaict the original study wasn't linked back then: https://news.ycombinator.com/item?id=20209569
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.
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.
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.
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.
Smart dog.
Smart dog.
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.
They’ll get away with whatever they can.
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.
At my Starbucks (and presumably others), dogs riding in a car in the drive-through regularly receive "puppercinos," a cup of whipped cream. I noticed how the dogs immediately go to the driver-side window and begin making eyes at the baristas.
Dairy Queen does something similar. Our dog does the same thing with the pup cups of soft serve they hand out.
The way you described your experiences gave rise to a question: are well-loved dogs already living a post-scarcity reality?
Yeah, seems like it. My dog lives a really easy life.
But it wouldn’t be a good life for a human or even a wild animal. My dog has no freedom or agency and is 100% reliant on me for food, exercise, entertainment, etc.
He can do what he wants within the limits of what I’ve trained him as acceptable (can go in the bed, but not the couch for example) but he isn’t free to leave. He is 100% subject to what I feel is best for him.
Now of course this relationship is mutually beneficial (I assume he’s happy - he gets healthy food, lots of exercise, and treats and toys as well as affection when he asks for it) but even if we had a true post scarcity world I would not want to live his life within the context that I’m a human.
But it wouldn’t be a good life for a human or even a wild animal. My dog has no freedom or agency and is 100% reliant on me for food, exercise, entertainment, etc.
He can do what he wants within the limits of what I’ve trained him as acceptable (can go in the bed, but not the couch for example) but he isn’t free to leave. He is 100% subject to what I feel is best for him.
Now of course this relationship is mutually beneficial (I assume he’s happy - he gets healthy food, lots of exercise, and treats and toys as well as affection when he asks for it) but even if we had a true post scarcity world I would not want to live his life within the context that I’m a human.
Yeah drive-throughs are required to have dog treats now because one drive-through had dog treats. Or at least that's what my dogs think.
Also they have a mental map of every single squirrel they've seen in town.
Also they have a mental map of every single squirrel they've seen in town.
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 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?
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?
Difficult to judge: Better sight doesn't mean "better human-like sight". Maybe dogs are better at seeing fast moving gradients (e.g. when racing prey), but have difficulties with slow changes (e.g. predator slowly closing in).
Also, maybe the dogs just assumed that /you/ would be looking out for any "enemies", and were then just surprised because you didn't warn them about the impeding "attack" while they had other things in mind ;-)
Also, maybe the dogs just assumed that /you/ would be looking out for any "enemies", and were then just surprised because you didn't warn them about the impeding "attack" while they had other things in mind ;-)
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I notice when I take my pup out to pee in the early morning that I'm much better at spotting wildlife than she is. We live in a pretty wooded area, so there are plenty of animals about. A deer staring at us, an owl looking down, a stray coyote heading home after a night's prowl, a fisher slinking back to the swamp... she won't notice any of them unless they're either very close, make a lot of noise, or if she can smell their trail. When she does notice them she gets very interested, so I don't think it's her not caring. It may well just be my higher line of sight.
Did your mother's dog have reflective eyeballs? If so, that's called a Tapetum Lucidum[0], and most dogs breeds have it. It's what make animals' eyes appear to glow in the dark. Light reflects off the back of the eye so the retina can absorb more of it, allowing for improved vision at night.
[0]https://en.wikipedia.org/wiki/Tapetum_lucidum
[0]https://en.wikipedia.org/wiki/Tapetum_lucidum
> Dogs vision is about 20/200 in general
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'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!
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!
Your comment about fetching led me to remember a Reddit post from the other day, where a dog (apparently also a Labrador or Lab mix) was able to fetch a single wood chip tossed a few meters away: https://www.reddit.com/r/videos/comments/h8dkjv/yogi_got_a_l...
This particular change is getting attention, but the trend is well-known:
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.
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.
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.
https://www.scientificamerican.com/article/is-the-gaze-from-...
https://www.scientificamerican.com/article/is-the-gaze-from-...
Entirely possible. I was taught the concept admittedly in a humanities course about Middle Eastern archaeology, and it was boiled down by the professor to, "We made our pets look cuter, more like babies. This made us feel more paternal towards them."
Related, humans have a bunch of neotenous features. There is even a Wikipedia article on it [1].
[1] https://en.wikipedia.org/wiki/Neoteny_in_humans
[1] https://en.wikipedia.org/wiki/Neoteny_in_humans
One theory is that humans self-domesticated while selecting for those who were more agreeable to living in civilization, similar Bonobos which also retain additional neotenous features.
https://www.scientificamerican.com/article/tame-theory-did-b...
https://www.scientificamerican.com/article/tame-theory-did-b...
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.
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:
https://en.wikipedia.org/wiki/Domesticated_red_fox
https://en.wikipedia.org/wiki/Dmitry_Belyayev_(zoologist)#Be...
https://en.wikipedia.org/wiki/Domesticated_red_fox
https://en.wikipedia.org/wiki/Dmitry_Belyayev_(zoologist)#Be...
This is really interesting. Does anyone know of any other instances of behavioral traits having a direct link to an animal's appearance?
Figure 2. Representatives of different families and orders show the most specific morphological markers of domestication, white spotting on the head (top row) and floppy ears (bottom row):
Horse, cow, pig, sheep, dog, and rabbit.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763232/
Horse, cow, pig, sheep, dog, and rabbit.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763232/
All behavioral traits have a direct relationship to phenotype.
What other at all reasonable way could it work?
What other at all reasonable way could it work?
One fox, Pushinka, even allegedly barked at an intruder like a guard dog.
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.
See https://en.wikipedia.org/wiki/Domesticated_red_fox#Experimen...
See https://en.wikipedia.org/wiki/Domesticated_red_fox#Experimen...
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.
http://www.bbc.com/earth/story/20150808-gorillas-with-human-...
> 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-...
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Yikes, I'd rather stair in the eyes of Darth Maul on a killing rampage
Y'all ignorant gorillas https://en.wikipedia.org/wiki/Cooperative_eye_hypothesis
Fascinating to see what my old university has been up to!
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.
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.