Did it all start with 10 types of dog?

Genealogical map reveals 10 top dogs

NewScientist.com news service

All of the hundreds of breeds of modern domestic dog, from the Afghan hound to the chihuahua, can be traced back to just 10 "progenitor" breeds, say US scientists.

Deborah Lynch of the Canine Studies Institute in Ohio, and Jenny Madeoy, of the Fred Hutchinson Cancer Research Institute in Washington State, studied canine physiology and behaviour, historical records and the available genetic information.

"It's a new way of thinking about purebred dogs," said Lynch. "For the first time we have identified progenitor breeds for each type."

Humans first domesticated wolves about 15,000 years ago, most probably to help them hunt. Domestication involves selectively breeding a species so that they can be controlled more easily. The latest genetic information suggests that the domestication of wolves first occurred in Asia.

Top 10

The researchers believe that by 10,000 to 12,000 years later, 10 "progenitor breeds" of dog had been created to fulfill different roles alongside their masters. It took a further 5000 to 3000 years for people to create the 300 or so pure breeds known today.

Retracing this breeding process is not a simple task, as the modern dog breeds show more physiological variation than is seen for any other species of mammal.

The 10 progenitors identified by the researchers are: sight hounds, scent hounds, working and guard dogs, northern breeds, flushing spaniels, water spaniels and retrievers, pointers, terriers, herding dogs and toy and companion dogs.

The sight hound, specialised for coursing game, is thought to have emerged in Mesopotamia around 4000 to 5000 BC. Modern breeds such as the greyhound and Afghan hound are found at the end of this branch of the canine family tree.

The scent hound meanwhile appeared around 3000 BC, characterised by a highly sensitised sense of smell and a body suited to warm weather. The bloodhound, foxhound, and dachshund are all thought to have descended from this dog.

Working and guard dogs probably emerged in Tibet around 3000 BC, with modern descendents including the rottweiler, the St Bernard's and the bulldog. At roughly the same time, toy and companion breeds apparently emerged in Malta. Modern descendents include the poodle and pug.


Genetic tree

"It's always interesting" to have this sort of family tree, says Gordon Lark, who is studying canine genetics at the University of Utah. But he says developing a genetic map, rather than a genealogical one will be more useful for understanding canine evolution, behaviour and health.

Scientists are expected to finish sequencing the dog genome within a year. This genetic data could be used to identify and treat dog illnesses, especially those common among purebreds.

And Lynch believes similarities between canine and human genetic code could enable scientists to use this information to study the genetic causes of some human diseases as well.

The study was presented at the annual meeting of the American Association for the Advancement of Science in Seattle, Washington.

Will Knight, Seattle