Science
17 April 2015:
Vol. 348 no. 6232 p. 277
DOI: 10.1126/science.348.6232.277
Vol. 348 no. 6232 p. 277
DOI: 10.1126/science.348.6232.277
- Feature
In
Science Magazine
A gray wolf.
PHOTO: © MARC MORITSCH/NATIONAL GEOGRAPHIC CREATIVE/CORBIS
Scientists who study canine origins seem to fight about everything: where dogs arose, when this happened, and even the best
way to find these answers. But there's one thing most of them agree on: how dogs became domesticated. Still, it's taken almost a century to get here, and the details are still emerging.
In 1907, the English scientist Francis
Galton suggested that dogs first entered our lives when our ancestors
nabbed some wolf
pups, brought them back to camp, and raised them as
pets. If you've ever seen a baby wolf, with its big eyes and oversized
ears, the idea doesn't seem so far-fetched—and,
indeed, Galton's hypothesis reigned for decades. But scientists
eventually
realized that domestication is a long, messy
process that can take hundreds or even thousands of years. These early
humans
may have started with a cute pup, but they would
have ended up with a wild animal.
So what did happen? Most experts now think
dogs domesticated themselves. Early humans left piles of discarded
carcasses at
the edges of their campsites—a veritable feast, the
thinking goes, for wolves that dared get close to people. Those wolves
survived longer and produced more pups—a process
that, generation by generation, yielded ever-bolder animals, until
finally
a wolf was eating out of a person's hand. Once our
ancestors realized the utility of these animals, they initiated a
second,
more active phase of domestication, breeding early
canines to be better hunters, herders, and guardians.
A massive collaboration that's trying to figure out where and when dogs emerged (see main story, p. 274)
has found some intriguing insights into the second phase of dog
domestication. A comparison of thousands of ancient dog
and wolf skeletons, for example, has revealed
flattening of the dorsal tips of ancient dog vertebrae, suggesting that
the
animals hauled heavy packs on their backs. The team
has also spotted missing pairs of molars near the rear of the jaw in
ancient
dogs, which may indicate that the animals wore some
sort of bridle to pull carts. These services, in addition to dogs'
hunting
prowess, may have proved critical for human
survival, potentially allowing modern humans to outcompete our
Neandertal rivals
and even eventually settle down and become farmers.
Now, a study on page 333
helps explains how man and dog took the next step to become best
friends. Takefumi Kikusui, an animal behaviorist at Azabu
University in Sagamihara, Japan, and his colleagues
have found that when dogs and humans gaze into each other's eyes, both
experience a rise in oxytocin—a hormone that has
been linked to trust and maternal bonding. The same rise in oxytocin
occurs
when human mothers and infants stare at each other,
suggesting that early dogs may have hijacked this response to better
bond
with their new human family.
The oxytocin study and the skeletal data
from the new collaboration go beyond clarifying the origin of the family
pet, says
collaboration leader Greger Larson, an evolutionary
biologist at the University of Oxford in the United Kingdom. “The more
that we know about the process of how dogs became
associated with people, the more we learn about the origins of
civilization.”
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