Dogs evolved to be cute

Dogs were one of the earliest animals to be domesticated, resulting in changes to their behaviour. But it also seems to have changed their appearance too.


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A 33,000 year old proto-dog skull from Beligum

A 33,000 year old proto-dog skull from Beligum

Wolves were one of the first animals to be domesticated, with genetic data indicating it may have occurred as early as 33,000 years ago. That’s over 20,000 years earlier than the domestication of wheat, sheep, cows and all the other classic creatures. This super-early domestication was believed to have been made possible by the fact wolves effectively domesticated themselves. Humans, being inherently messy animals, provided a great source waste and scraps for an animal to live off. The tamer and less aggressive an animal was, the more likely their scrounging was to be tolerated around the campsite. Thus evolution pushed them in that direction until we got the delightful, less bitey dog who we’re happy to feed scraps to.

But some researchers wondered whether evolution was being a bit more cynical than that. Dogs are highly paedomorphic, meaning that they retain child-like traits well into adulthood. Their face (and facial expression) in particular are more similar to wolf pups than to adult wolves. The researchers wondered whether this might be the result of an evolutionary push to make early dogs more appealing to hunter-gatherers, playing on their heart-strings by tapping into our love for big eyes and cute faces.

So these scientists went to an animal shelter and quantified how paedomorphic the facial expressions of various dogs were. They then looked to see which dogs were adopted by the easily manipulated humans. And sure enough, they found a fairly strong correlation between one paedomorphic trait in particular and a dogs’ chances of being adopted. The more likely the dog was to raise their inner eyebrows when being observed by potential owners, the more likely those humans were to become actual owners.

A dog being normal, then raising up the inner eyebrow.

A dog being normal, then raising up the inner eyebrow.

Several other puppy-like traits were linked to chance of adoption, and some were actually negatively correlated. Perhaps most surprisingly, the more a dog wagged its tail the less likely it was to be adopted! But none of these had an effect as significant as the inner eyebrow raising. So if you ever find yourself reincarnated as a dog and want to please humans, start doing that.

Based on all this the researchers concluded that the domestication of dogs was not just about them loosing aggression so they would be tolerated by humans; but actively becoming appealing to hunter-gatherers through paedomorphic characteristics. This is the first piece of evidence that suggests this (although you could’ve probably guessed it may have been involved). Of course, there may be other factors at work. The researchers point out that the movements of the inner eyebrow are often associated with sadness, and that might be what the adopters were picking up on rather than an inherent preference for paedomorphism. And there’s the obvious one: this study wasn’t conducted on hunter-gatherers deciding if they should let a wolf hang around their camp because it looks cute.

Still, this study is dealing with real actions: people adopting dogs. It’s all to easy to say “I like this” on a survey and for researchers to extrapolate out some grand evolutionary conclusions for all this. The fact people are willing to invest time and effort in animals based on these characteristics suggests that there is a real effect there, although I doubt we’ll ever know for sure just how strong a role it played in the domestication of dogs. But then, that’s science for you: a finicky, uncertain mistress. Kinda like my girlfriend.

As an aside, one of the researchers involved in the study works from Mars; the company that owns Pedigree. So if you start seeing dogfood commercials involving a lot of eyebrow raising, this is why. They’re trying to replicate the evolutionary success of the domestic dog.

References

Thalmann O, Shapiro B, Cui P, Schuenemann VJ, Sawyer SK, Greenfield DL, Germonpré MB, Sablin MV, López-Giráldez F, Domingo-Roura X et al. . 2013. Complete mitochondrial genomes of ancient canids suggest a European origin of domestic dogs. Science 342(6160):871-874.

Waller BM, Peirce K, Caeiro CC, Scheider L, Burrows AM, et al. (2013) Paedomorphic Facial Expressions Give Dogs a Selective Advantage. PLoS ONE 8(12): e82686. doi:10.1371/journal.pone.0082686

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17 thoughts on “Dogs evolved to be cute”

  1. Jim Birch says:

    Cats – who were domesticated much later, to protect grain stores – also seem to have departed from wild cat looks and developed features that resemble human babies: the big eyes and the round face (albeit hairy.) And, of course, the meow, which sounds rather like a wailing child. Interestingly, cats only deploy the meow on humans, not on each other.

    1. Adam Benton says:

      Whilst I’m not sure about how paedomorphic cats are (although it seems likely they are quite a bit) the dog article does cite the cat meow thing as an example of how animals have evolved/developed some ingenious strategies to ingraciate themselves with humans

      1. mgm75 says:

        Certainly a dog’s facial expression is more animated than a cat’s I feel that cats are capable of only two faces: derision and slyness 😛

        Very good article, and it certainly shows once again the appeal of dogs throughout their and our evolution. It’s an interesting and perhaps accidental co-dependency in suggesting that the tamer dogs were effectively “permitted” around the camp sites of hunter-gatherer societies.

        1. Adam Benton says:

          Cynthia raises a good point in some other comments I missed here; in that it need not have been around camps. Both wolves and humans are hunters, so learning to tolerate each other out in the wild may have had made the hunting process easier for both

  2. Mados says:

    Hm… I would hardly call it “evidence”, more like a case of correlation = causation (except where it counters the hypothesis) assumptions.. and plenty of other unstated assumptions too.

    Shelter adopters in highly anthropormophised and urbanised society in the 2010s = small hunter-gather camps 30.000+ years ago? Raising inner eye brows = looks like a human baby? Traits that get shelter dogs adopted = traits that evolved because they made volves more adoptable, except e.g. tail wagging, because that doesn’t count?

    There have been many studies about dog’s paedomorphic traits… a well known dog-fact, and many of them thorough and interesting and there is a lot more to it than cuteness.

    And what about ourselves? Humans are paedomorphic too (retain primate childlike characteristics)… that’s something we have in common with dogs… so is our evolutionary success also due to being cute? Although some individual may do well on that basis thus have had a better chance to pass on their genes, there is obviously a lot more to it than just how we look.

    Same with dogs, although whether dogs look pleasing to humans has obviously had a dramatic impact on the evolution of pedigree dogs the last few hundred years… but probably not that much on, let’s say, Indian stray village dogs. The topic is way too complex for such simplistic conclusions.

  3. john zande says:

    One of my rescue dogs has perfected the Oliver Twist, “Please sir, may I have some more” posture when asking for dinner left-overs. It’s astonishing. She wants for nothing, is as healthy as a finely tuned German engine, but damn can she turn it on! She can even turn her hinds paws in, pigeon-toed, to enhance the pathetic look she’s aiming for. That’s of course behavioural, not genetic, but it leaves me astounded every time.

    1. Adam Benton says:

      Perhaps the story needs a bit of revision. We didn’t begin to tolerate dogs, they figured out how to exploit us

      1. john zande says:

        That’s probably a little closer to the truth… Certainly true of cats.

        1. Adam Benton says:

          Are they even domesticated yet? 😛

        2. john zande says:

          The one presently sitting on my desk is sure pretending to be, but i can see through his ways 😉

        3. Jim Birch says:

          Evolution is all about exploitation. We exploited cats to kill vermin, they exploited us for shelter and supplementary food.

          Some animals, particularly mammals, developed even more powerful exploitation opportunities, paradoxically, through the addition of cooperative strategies to the toolbox. Humans are in a league of their own: our cooperative urges have been so mythologised that we are surprised to find that cats are exploiting us. We though we were all just being nice. 🙂

        4. Adam Benton says:

          True. People talk about symbiotic relationships; but these are really just cases where two groups can exploit each other without either suffering too much

  4. Cynthia Echterling says:

    The big-eyed begging look works for children and adult supplicants as well as dogs and cats. But I have a feeling the relationship between canid and homo goes way back long before domestication. Wolves had better tracking skills and we could kill game they couldn’t take on such as woolly mammoths and rhinos. So it may have been expedient for the two diurnal pack hunters to keep an eye out for what the other was hunting. There may have been a symbiotic relationship similar to that between ravens and wolves. Ravens find prey or carcasses, let the wolves know, then move in once the animal has been ripped open by the wolves. This could have been going on a long time without any genetic change. Perhaps later, in times of scarcity, the wolves began coming closer to feed of our rubbish as pariah dogs do today. Then the domestication began. Based on the Russian experiments with foxes, it took eight generations of controlled breeding for tameness to produce foxes that sought the attention of humans and with that came physical changes that we see in dogs such as shortened faces, white markings, floppy ears and curly tails.

    1. Adam Benton says:

      The fox study is fascinating because of the speed at which it happened. If a time of scarcity was the driver towards dog self-domestication; then it need not have been a hugely long period.

      1. Wyrd Smythe says:

        Also fascinating for how they reversed it, breeding for wild traits, and had feral foxes again in a similarly short time span.

  5. Jim Birch says:

    The physical changes suggest that some of the maturation genes are knocked out. It would also be interesting to know what happened to testosterone levels too. I guess domesticated animals have lower levels.

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