Why Dogs Chose Man: It's All About the Love Hormone

By Ken Tudor, DVM on Apr. 7, 2015

When you hear the word “oxytocin” you probably think of moms nursing and bonding with their babies. This hormone, oxytocin, is also known as the “bonding hormone.” But its power is not limited to human bonding.

A new study from Australia suggests that the hormone of love may have played a role in leading wild dogs to man’s fires and eventual domestication.

What is “Oxytocin”?

Oxytocin is a hormone produced in the hypothalamus of the brain and released from the back half (posterior) of a pea sized pituitary gland. Oxytocin is important for sexual arousal in both sexes for orgasm and sexual reproduction. It is particularly important for its effect on the cervix and uterus during childbirth and breast nipple stimulation that causes milk “letdown” for nursing.

The effects of oxytocin on other parts of the brain during these activities are thought to bring about positive pair bonding, maternal bonding, and positive social recognition bonds. A PhD researcher at Monash University in Melbourne, Australia, has found that oxytocin plays a role in the interactions between dogs and humans.

Why Oxytocin May be Important in the Domestication of Dogs

Previous studies have shown that just three minutes of petting and talking to a dog increases blood oxytocin levels in both dogs and humans. Other studies have shown that humans who are particularly close to their dogs have more oxytocin in their urine. This data lead Jessica Oliva to conduct her PhD thesis experiment.

62 dogs, 31 male and 31 female, were tested to see if oxytocin increased their ability to read cues from humans to the whereabouts of bowls with hidden treats. The dogs were scored on their abilities after receiving either a nasal administration of oxytocin or a saline placebo. Nasal spray was used because it ensures the direct passage of oxytocin to the brain in order to eliminate other factors that could cloud the response results.

Not only did the dogs respond more accurately when given oxytocin, but the enhanced performance lasted 15 days after administration of the oxytocin. Oxytocin in some way aids a dog’s ability to read human cues. This far exceeds the ability of wolves to do the same. Oliva cited research that has shown dogs were far better at using non-verbal cues from humans than even wolves that were highly socialized and hand-reared by humans.

This research only demonstrates the role of oxytocin in man’s relationship to dogs but does not explain the exact brain interactions involved. Oliva wants to conduct the same experiment on wolves to see if there is a different result. That would really help clarify the evolutionary separation of the wild dog from wolves and their eventual domestication.

She also suggests that the identification of a genetic sensitivity to oxytocin in modern dogs may lead to better performing dogs. This could have an impact on breeding dogs that may be better suited as guide or service dogs, military dogs, or customs dogs.

Maybe the dog-human bond boils down to a famous song lyric, “All you need is love.” Thanks oxytocin.

Dr. Ken Tudor

Image: Mat Hayward / Shutterstock


Ken Tudor, DVM


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