Sleeping with wolves: The evolution of human relationships with dogs

Contrary to popular belief, dogs may not be direct descendants of any wolf species alive today. Recent DNA analysis raises the possibility that both dogs and existing wolves may have descended from a common wolf or wolf-like ancestor. However, dogs and wolves are closely related due to this shared genetic heritage. The earliest evidence of domestication of dogs is dated at around 14,000 years ago, though it may have begun earlier than this. There is evidence of ritual burying of dogs (as if they were family members) dating from 12,000 to 14,000 years ago. Complex behavioural changes take a very long time to evolve, and in some ways, the dogs who live in our houses and sleep in our beds are still quite similar to their wolf-like ancestors and wolf cousins in that they are very territorial pack animals. Dogs and wolves remain similar enough for breeding to be possible, resulting in wolf-dog hybrids. However, humans have selectively bred many types of dogs to be less aggressive than wolves.Keeping pets appears to be almost unique to humans. There are some wonderful examples of cross-species ‘friendships’ (my favourite being ‘The Cat and the Crow’). There are even occasional examples of what appears to be pet-keeping in great apes and monkeys, but often they end badly as a result of less than gentle handling! However, Herzog argues that these examples usually involve human agency and are rare in the wild.

Yet keeping dogs as pets is now a near universal aspect of human culture.  Humans often form extremely strong attachments to dogs. We love them deeply, often as if they were our own children. In one study, almost half of the dog owning participants said they saw their dog as a member of their family. Many of us even let our dogs sleep in our beds, and almost three quarters of the participants in the study said that their dogs slept in their bedrooms. It was also common to celebrate birthdays – forty per cent of participants reported this. Here is my friend’s dog, Brody, enjoying his birthday cake, specially made for his second birthday: For dogs, there are clear fitness benefits to living with humans: they are protected, housed, fed and entertained. They no longer have to fend for themselves in the wild. But explaining why humans keep dogs is challenging for evolutionary psychology. If I asked you why you have a dog, you might say that you just like dogs, that your dog is fun to be with, that you love your dog… you might give me any number of reasons. However, from an evolutionary perspective, these answers don’t help because part of what requires explanation is the enjoyment we find in taking care of dogs and spending time with them.

Dogs in particular require a lot of financial investment, needing food, toys, and medical care. They also require a lot of time, needing walks (whatever the weather) and attention, and they cannot be left alone for long periods of time. Some owners pay for the equivalent of childcare for their dogs while they are at work, and ‘doggy daycare’ isn’t a whole lot cheaper than human childcare. This is puzzling behaviour because we humans have evolved to invest in our own genetic offspring, so that they in turn reproduce, and our genes are replicated. This tendency to help relatives who share our genes is called kin altruism. Clearly, diverting some of this investment to members of another species seems counter-productive. John Archer argues, from an evolutionary perspective, that pet ownership is detrimental to our reproductive success because of the costs associated with their attachment and the investment needed. He suggests that we keep pets because they manipulate adaptive responses which were selected to enable care-giving, particularly to our children. Animals achieve this through several mechanisms. We tend to respond most strongly to animals with neotenous features, i.e. those that are similar to the features of a human baby’s face – large eyes, chubby cheeks, and a large forehead. The animals we most commonly keep as pets often have these features. We respond strongly to these features with the desire to care because we evolved to respond to our own offspring with care-giving behaviour since they require it to survive and reproduce themselves. Disney’s Bolt provides, I think, the ultimate illustration of how dogs use neoteny to manipulate humans – this is my favourite part of what is, for me, Disney’s most underrated and best film:

Humans have unconsciously bred dogs to have these neotenous features because they are attractive to us. Paradoxically, these features allow dogs to better exploit us. Archer argues that pet owners often treat their pets just as if they were children, citing research showing that pet owners often cuddle their pets as if they were children, talk to them in motherese (the form of language that we use to talk to infants) and call them baby. I confess I often call my cat ‘baby girl’, to rebukes from my son who correctly reminds that she is in fact a middle-aged adult!

My cat – Minerva

Dogs have some additional qualities that allow them to exploit our care-giving tendencies. Their evolutionary history as social pack animals has endowed them with a keen ability to be attentive to different individuals, and to understand and respond to them. Dogs tend to know who everyone is and where they are at all times. Dogs also appear to show emotional responses. They seem to understand when their owners are sad or annoyed. They also appear to show guilt when they have done something wrong. These responses delight us because they are so like our own, and they allow us to feel a deep connection to our dogs, I have to admit that looking at photos and videos of ‘guilty dogs’ is one of my favourite ways to waste time and never ceases to amuse me. Here is my favourite – Denver, The Guilty Dog! This never gets old…

Dogs also show reciprocal attachment to their owners and their love often seems unconditional. These human-like – sometimes super-human in the case of unconditional love – features help us to anthropomorphise dogs, and this further enhances our attachment to them. What could be better than the ecstatic welcome of a dog who loves you?

Dogs really do seem to love us. Research is starting to reveal the biological underpinnings of their attachment to us. The neurohormone oxytocin facilitates attachment in humans. For example, it is released when mothers and babies gaze at one another, and during breastfeeding. Oxytocin and gaze also appear to be important in human-canine attachment. In one study, researchers measured the effect of gaze on oxytocin levels by measuring levels of the hormone in urine. They found that gazing for longer resulted in more oxytocin in the urine of both the dogs and their owners, but no such relationship was found for wolves raised by humans. The researchers also examined the effect of oxytocin on gazing, finding that dogs who had been administered oxytocin nasally spent longer gazing at their owners, and this led to an oxytocin rise in their owners. This shows the reciprocal nature of the attachment process in dogs and humans (the researchers didn’t administer oxytocin to the wolves though – would you want to try getting a wolf to inhale hormones?!).

The extent of a dog’s attachment to a human is partly explained by the particular version of an oxytocin receptor gene the dog has. Researchers extracted DNA from border collies and German shepherds and found three different versions of the gene. The extent of friendliness towards humans depended on the version of the gene the dogs had. So, some dogs do love more intensely than others.

The research on oxytocin and gaze suggests that the attachment process between humans and dogs operates in the same way as mother-infant attachment, which also depends on gaze and oxytocin. Dogs appear to have hijacked this attachment system, and this has allowed them to form loving relationships with humans, providing them with food and protection. Despite the endless love shown by our dogs, Archer concludes that pets are ‘social parasites’ and do not provide mutual benefit. This is not as bad as it sounds. What Archer means is that having dogs as pets is detrimental to our ability to pass on our genes. This is because dogs divert investment that could be made in our human offspring, Look at this this way: The money someone spends on keeping a dog could be spent on their own children instead. This might improve their children’s health or their education and these things would be beneficial to their reproductive success. Even when economic resources are not an issue, dogs take up a lot of time, which also could have been invested in children. Some people even choose to own dogs instead of having children.

From an evolutionary perspective, such behaviour seems maladaptive. Archer is not arguing that that we do not get pleasure from pet ownership, quite the contrary. But he is arguing that we get pleasure from it because pets parasitise adaptive mechanisms designed to help us to care for our offspring. He compares pets to cuckoo chicks who are raised by mothers of a different species because their parents left their eggs in her nest. The adoptive mother does not realise that she is raising the offspring of another bird (despite its often comparatively enormous size), and so investment is diverted away from her own offspring, into a baby who cannot help her to pass on her genes. Yet she happily takes care of the baby cuckoo because it has hijacked the brain mechanisms which evolved to ensure that she cares for her own babies. Of course we do know that dogs are not our own babies, but that does not stop our evolved attachment mechanisms from responding to them as if they were.

A reed warbler raising an enormous cuckoo chick

Archer also acknowledges the growing body of research which demonstrates health benefits of pet ownership, but he argues that generally the benefits are relatively small compared to the costs, and so overall there is still a fitness loss at the genetic level. I am partly convinced by Archer’s argument. However, he is discussing pet ownership more generally (though he mainly focusses on dogs and cats). I think most people will find his argument more convincing in relation to cats. Although often affectionate, cats are typically viewed as more solitary and selfish creatures, and rarely show the same exuberance of emotion as dogs.

But not everyone agrees with Archer about the nature of human-canine relationships. When dogs first began living with humans, they may have provided some significant fitness benefits. Groves has made the case for a more symbiotic rather than parasitic relationship. He argues that dogs would have provided significant advantages to our hunter-gatherer ancestors in terms of things like of hunting ability, detecting danger, and providing protection and warmth. He sees the domestication process as a mutual one, whereby dogs domesticated us as we domesticated them. Even today, we use dogs for a variety of things that humans are less effective at. Dogs act as security guards, protectors, guide dogs, drug detectors, herders, and even entertainers and therapists. Just this week there were reports in the press about an NHS trial using dogs to detect cancer. However, there are some less noble reasons for dog ownership, which also have an evolutionary basis. In a study addressing the darker side of pet ownership, Beverland and colleagues argue that expensive designer dogs and rare breeds may serve as symbols of conspicuous consumption, a term coined by Thorstein Veblen in his book The Theory of The Leisure Class in 1879. Veblen argued that wealthy people do not buy expensive, luxury goods to directly increase their happiness, but as a means of displaying their wealth to others.

From the perspective of modern evolutionary psychology, conspicuous consumption serves as an honest indicator of wealth and is likely to be attractive to a potential mate. In addition, the type of dog a person chooses may be a signal to potential mates of their personality. Beverland and colleagues interviewed dog owners about their reasons for choosing their dog. Some dog owners did value their dogs as individuals, saw them as family members, and wanted them for the pleasure they gave. However, others saw their dogs as part of their own identity and valued them more for their ability to signal aspects of their personal identity to others.

A Tibetan mastiff – one of these sold for over one million pounds

Another manifestation of the tendency to use dogs as status symbols is the phenomenon of dangerous dog owning amongst young men. For low status men living in deprived socioeconomic areas, dangerous dogs are sometimes an important part of culture. These dogs are the antithesis of the cute, neotenous pets that invoke our parental instincts. They are mastiffs and dobermans, pit bull terriers and rottweilers. Sometimes they are bred for viciousness, and some owners even view them as being ‘made out of death‘. Some of the more exotic crossbreeds can cost thousands, and therefore they do signal status via conspicuous consumption. But more than that, they can offer their owners protection, and enhance status further as a display of threat and strength. The dogs sometimes act as proxies for their owners as they fight to the death to settle status disputes on their behalf.  As I discussed in my posts on the evolutionary basis of gangs, status acquisition is essential for young men seeking to attract women. High status is one of the primary aspects of mate quality that women seek in a partner because it indicates good genes, and  the ability to protect and provide for offspring. For men born into poor socioeconomic areas, the routes to higher status are often limited, and sometimes involve aggression and physical domination of others. Owning dangerous dogs is an extension of this.

However, some research may indicate that men who own dangerous dogs are ‘barking up the wrong tree’ (sorry!). It has been suggested that caring for a pet can serve as an indicator of parental ability, and may therefore enhance attractiveness. Some researchers in France provided support for this argument. They found that a man was three times more successful in obtaining the phone numbers of women when he had a dog with him! This may be less effective with a more dangerous (and therefore less neotenous) dog; one study found that people with labradors were approached more often than those with rottweilers.

When dogs and humans first teamed up then, there may well have been reproductive benefits for both species. In the modern world, however, we no longer benefit much from the hunting abilities and predator detection offered by dogs. Whilst dogs can still offer some protection and status benefits, these are not a priority for most of us. The majority of dogs are not working dogs or status symbols, but beloved family pets. For most people then, in pure biological fitness terms, dogs may impose more costs than benefits in the modern world. However, the research on caring for dogs as an indicator of parenting ability is an interesting new avenue of research, and indicates potential fitness benefits.

But even if dogs have just hijacked our evolved mechanisms for parental care, does it matter when they are as cute as this?

Hamish

And given the extent of castration and neutering practices now, there are rarely fitness benefits for them either!