7 ms·

Dogs' Eyes Have Changed Since Humans Befriended Them (2019)

81 points by EndXA 6y ago

wrnr 6y ago
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.
- wrnr 6y ago
  Y'all ignorant gorillas https://en.wikipedia.org/wiki/Cooperative_eye_hypothesis https://en.wikipedia.org/wiki/Cooperative_eye_hypothesis
- lowdose 6y ago
  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-eyes http://www.bbc.com/earth/story/20150808-gorillas-with-human-...
  - wrnr 6y ago
    Yikes, I'd rather stair in the eyes of Darth Maul on a killing rampage
  - deleted 6y ago
    [deleted]
cpwright 6y ago
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.
- luckylion 6y ago
  > 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?
  - deleted 6y ago
    [deleted]
  - archi42 6y ago
    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 ;-)
  - technothrasher 6y ago
    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.
  - fingerlocks 6y ago
    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 https://en.wikipedia.org/wiki/Tapetum_lucidum
taneq 6y ago
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.
annamargot 6y ago
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.
- teraku 6y ago
  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.
EndXA 6y ago
The original study can be read here: https://www.pnas.org/content/116/29/14677 https://www.pnas.org/content/116/29/14677 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 6y ago
  Was already posted in 2019 (251 points), but afaict the original study wasn't linked back then: https://news.ycombinator.com/item?id=20209569 https://news.ycombinator.com/item?id=20209569
gadders 6y ago
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.
- nemo44x 6y ago
  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.
  - yourapostasy 6y ago
    The way you described your experiences gave rise to a question: are well-loved dogs already living a post-scarcity reality?
    - nemo44x 6y ago
      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.
kingkawn 6y ago
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/Domesticated_red_fox https://en.wikipedia.org/wiki/Dmitry_Belyayev_(zoologist)#Belyayev's_fox_experiment https://en.wikipedia.org/wiki/Dmitry_Belyayev_(zoologist)#Be...
- tsdlts 6y ago
  This is really interesting. Does anyone know of any other instances of behavioral traits having a direct link to an animal's appearance?
  - Cactus2018 6y ago
    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/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763232/
  - kingkawn 6y ago
    All behavioral traits have a direct relationship to phenotype. What other at all reasonable way could it work?
- kipchak 6y ago
  One fox, Pushinka, even allegedly barked at an intruder like a guard dog.
z3t4 6y ago
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.
- akeck 6y ago
  More info: https://blogs.scientificamerican.com/guest-blog/mans-new-best-friend-a-forgotten-russian-experiment-in-fox-domestication/ https://blogs.scientificamerican.com/guest-blog/mans-new-bes...
- throwawayffffas 6y ago
  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#Experimentation https://en.wikipedia.org/wiki/Domesticated_red_fox#Experimen...
alexpotato 6y ago
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.
AdmiralAsshat 6y ago
This particular change is getting attention, but the trend is well-known: https://en.wikipedia.org/wiki/Neoteny#In_domestic_animals 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.
- war1025 6y ago
  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 https://en.wikipedia.org/wiki/Neoteny_in_humans
  - kipchak 6y ago
    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-bonobos/ https://www.scientificamerican.com/article/tame-theory-did-b...
- kipchak 6y ago
  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-those-big-puppy-eyes-the-look-of-your-doggie-s-love/ https://www.scientificamerican.com/article/is-the-gaze-from-...
  - AdmiralAsshat 6y ago
    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."
bitwize 6y ago
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.
- gumby 6y ago
  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.
mrlonglong 6y ago
Fascinating to see what my old university has been up to!

81 points by EndXA 6y ago

wrnr 6y ago

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.

wrnr 6y ago
Y'all ignorant gorillas https://en.wikipedia.org/wiki/Cooperative_eye_hypothesis https://en.wikipedia.org/wiki/Cooperative_eye_hypothesis
lowdose 6y ago
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-eyes http://www.bbc.com/earth/story/20150808-gorillas-with-human-...
- wrnr 6y ago
  Yikes, I'd rather stair in the eyes of Darth Maul on a killing rampage
- deleted 6y ago
  [deleted]

cpwright 6y ago

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.

luckylion 6y ago
> 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?
- deleted 6y ago
  [deleted]
- archi42 6y ago
  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 ;-)
- technothrasher 6y ago
  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.
- fingerlocks 6y ago
  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 https://en.wikipedia.org/wiki/Tapetum_lucidum

taneq 6y ago

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.

annamargot 6y ago

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.

teraku 6y ago
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.

EndXA 6y ago

The original study can be read here: https://www.pnas.org/content/116/29/14677 https://www.pnas.org/content/116/29/14677 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 6y ago
Was already posted in 2019 (251 points), but afaict the original study wasn't linked back then: https://news.ycombinator.com/item?id=20209569 https://news.ycombinator.com/item?id=20209569

gadders 6y ago

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.

nemo44x 6y ago
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.
- yourapostasy 6y ago
  The way you described your experiences gave rise to a question: are well-loved dogs already living a post-scarcity reality?
  - nemo44x 6y ago
    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.

kingkawn 6y ago

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/Domesticated_red_fox https://en.wikipedia.org/wiki/Dmitry_Belyayev_(zoologist)#Belyayev's_fox_experiment https://en.wikipedia.org/wiki/Dmitry_Belyayev_(zoologist)#Be...

tsdlts 6y ago
This is really interesting. Does anyone know of any other instances of behavioral traits having a direct link to an animal's appearance?
- Cactus2018 6y ago
  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/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763232/
- kingkawn 6y ago
  All behavioral traits have a direct relationship to phenotype. What other at all reasonable way could it work?
kipchak 6y ago
One fox, Pushinka, even allegedly barked at an intruder like a guard dog.

z3t4 6y ago

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.

akeck 6y ago
More info: https://blogs.scientificamerican.com/guest-blog/mans-new-best-friend-a-forgotten-russian-experiment-in-fox-domestication/ https://blogs.scientificamerican.com/guest-blog/mans-new-bes...
throwawayffffas 6y ago
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#Experimentation https://en.wikipedia.org/wiki/Domesticated_red_fox#Experimen...

alexpotato 6y ago

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.

AdmiralAsshat 6y ago

This particular change is getting attention, but the trend is well-known: https://en.wikipedia.org/wiki/Neoteny#In_domestic_animals 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.

war1025 6y ago
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 https://en.wikipedia.org/wiki/Neoteny_in_humans
- kipchak 6y ago
  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-bonobos/ https://www.scientificamerican.com/article/tame-theory-did-b...
kipchak 6y ago
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-those-big-puppy-eyes-the-look-of-your-doggie-s-love/ https://www.scientificamerican.com/article/is-the-gaze-from-...
- AdmiralAsshat 6y ago
  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."

bitwize 6y ago

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.

gumby 6y ago
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.

mrlonglong 6y ago

Fascinating to see what my old university has been up to!