Dear Science,
Why does my dog’s tail wag? When I was a kid, I was told dogs wag
their tails when they’re happy, but she really wags it a lot and all
the time. No one can be that happy, not even a dog. Can they?
Barking
The answer lies in why there is a dog in your house at all. The
genetic evidence tells us that dogs were the first domesticated
creatures, around the time modern humans evolved. How did that happen? Trash. According to the in-vogue theory, dogs started as
wolves with a hankering for the piles of refuse surrounding human
settlements. Only after wolves tamed themselves could primitive
humans selectively breed or train dogs. It’s a beautiful idea, but
difficult to prove. (A colleague sardonically quipped, upon hearing
this theory, “Those primitive hominids sure took good notes,
didn’t they?”)
Luckily for us, Siberian winters are long. Russian geneticist Dr.
Dmitry Belyaev, presumably tired of being bit and bored, started a
long-running breeding experiment with wild foxes. In the experimental
group, only the foxes least afraid of or most likely to approach humans
were allowed to breed. In the control, breeding was random. No big
surprise, the selectively bred population became increasingly tame
toward humans. More unexpectedly, the foxes also gained mottled
hair, floppy ears, and curly tails—similar to dogs. The biggest
treat: The tame foxes started to understand human social cues.
Dogs are the most humanlike creature, at least when it comes to
social skills—closer than our genetic cousins chimpanzees and
bonobos. Try to direct your dog to some hidden toy in your apartment
just by looking or pointing. She’ll have no trouble. Fourteen-month-old
human children, well before language develops, also find the game easy.
Chimps—smarter than dogs in most ways, but more
volatile—fail miserably. Dogs come preprogrammed to recognize
where a human is pointing, gazing, or nodding; a chimp must first learn
each of these tricks. Such abilities require the temperament of a dog,
something a chimp or a wolf lacks. Take a litter of wolf or dog pups
and raise them the same way. The dogs will inherently respond to humans
with much more grace than the wolves, even with the same training. One
of the biggest differences: Wolves rarely wag their tails, doing
it only when they’re actively submitting; dogs cheerfully wag their
tails all the time.
So why does your dog wag her tail? To show a deeply selected
trait for benign temperament—a rare, socially lubricating
spirit shared by humans and dogs. It makes Science wonder how our
dispositions—relatively agreeable compared to those of chimps,
and required for human-to-human interaction—were pulled by our
canine companions.
Evolutionarily Yours, Science
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