YA-PING ZHANG
Blueblood. This Chinese working dog may represent one of the oldest
lineages of dogs, as new data suggest wolves were domesticated first in
China.
Study Reasserts East Asian Origin
for Dogs
By Elizabeth Pennisi 1 September 2009
The latest "made in China" item isn't a plastic widget or a pair of
shoes. It's a dog. A new study suggests that wolves were first
domesticated in Southeast Asia some 16,000 years ago. The
work is the latest volley in a long-standing debate about just
where canine companionship got its start.
Most researchers agree that dogs descended from wolves, but
when and where has been hard to pin down because
archaeologists have trouble telling wolf remains from dog
remains. So in the past decade, geneticists have started to look
at DNA for clues. In 2002, geneticist Peter Savolainen of the
KTH-Royal Institute of Technology in Stockholm and colleagues
analyzed mitochondrial DNA from 38 wolves and more than
500 dogs around the world. They found the most genetic
diversity--a marker of a species' origin--in East Asia and
concluded that dogs were domesticated there, and just once.
But last month, a study of African village dogs called that
conclusion into question. Computational biologists Adam
Boyko and Carlos Bustamante of Cornell University and their
colleagues sampled more than 300 village dogs from Egypt,
Namibia, and Uganda. The genetic diversity of the African
village dogs was on par with that seen in East Asian dogs, they
reported online 3 August in the Proceedings of the National
Academy of Sciences. Boyko and Bustamante don't think that
dogs originated in Africa, however, because gray wolves, the
dog's likely predecessor, are not found on that continent. But
the work did seem to argue that Savolainen's genetic diversity
data weren't strong enough to support his conclusions for an
East Asian origin.
Now Savolainen, Ya-Ping Zhang of the Chinese Academy of
Sciences' Kunming Institute of Zoology, and their colleagues
have done an even more extensive survey of dog DNA. They
looked at a small piece of mitochondrial DNA from more than
1500 dogs distributed across Europe, Africa, and Asia, with an
emphasis on East Asia. Some were breeds with known
geographic origins; others were working dogs in rural areas.
The researchers also looked at 40 wolves. They then sequenced
almost all of the mitochondrial genome from eight wolves and
from 169 dogs representing the range of diversity identified in
the initial 1500-plus animals.
The data reaffirm a single site for domestication and pinpoint
the origin of the domesticated dog to a region south of the
Yangtze River, where wolf taming was quite common,
Savolainen's team reports today in Molecular Biology and
Evolution. That's where the largest number of similar groupings
of DNA, called haplogroups, is found. As the researchers looked
at dogs farther from this region, they saw fewer haplogroups;
Europe had only four, for example. "The gene pool we are
finding in Europe and Africa are a subset of the South Chinese
gene pool," says Savolainen.
Savolainen's critics have noted that low diversity in European
dogs might be the result of intense selective breeding, and thus
it may not reflect the ancient diversity of dogs there. But the
European dogs all lack the same six haplogroups, regardless of
breed, indicating that the lower diversity preceded the
development of purebred strains, Savolainen says.
The study "is the most compelling evidence for the origin of the
dogs published to date," says Hannes Lohi, a veterinary
molecular geneticist at the University of Helsinki. "The data here
[are] very much similar to corresponding human data for the
out of Africa evidence. It looks like dogs were 'created' in
China."
Bustamante is impressed, albeit cautious. "It's a solid study and
an important study," he says. "But the conclusion that there was
one and only one center of domestication is premature." He
and others point out that researchers need to see if the pattern
of diversity holds up in nuclear genes, which might tell a
different story. More wolves need to be analyzed as well to
correlate their haplogroups with those seen in dogs.
Carles Vilà of the Biology Station of Doñana-CSIC in Seville,
Spain, is even more cautious. He points out that other genetic
studies suggest dogs date back at least 20,000 years and that
archaeological remains of dogs in Europe are almost as old. He
also worries about bias that might have arisen in Savolainen's
study if the dogs were not sampled the same way in all
locations. "I'm not convinced by the results," he says, "and I do
not think this is the last that we will hear about the time and
place of the domestication of dogs."