Man’s proverbial first best friend was probably a grey wolf that may have made contact with the first human companions about 33,000 years ago, somewhere in south-east Asia.
About 15,000 years ago, a small pack of domesticated dogs began trotting towards the Middle East and Africa. Canis lupus familiaris made it to Europe about 10,000 years ago, and when civilisation began in the Fertile Crescent, and humans began to build farmsteads and villages with walls, dogs were already there to help keep guard, herd the first flocks, and demand to be taken for a walk.
The details of the story – the characters, the action and the precise locations – are unknowable. But the outlines of the great adventure are written in DNA.
Scientists from China, Canada, Finland, Singapore, Sweden and the US report in the journal Cell Research that they compared the genomes, or genetic inheritances, of 58 canids. These included 12 grey wolves, 12 indigenous dogs from the north Chinese countryside, 11 from south-east Asia, four village dogs from Nigeria and 19 specimens of selective breeding from Asia, Europe and the Americas, including the Afghan hound, the Siberian husky, the Tibetan mastiff, the chihuahua and the German shepherd.
Because each genome is a text copied (with regular misspellings, or mutations) through the generations, and every genome is related to every other genome, any comparison begins to tell a story of family connections and separations long ago. The more “texts” that can be compared, the more certain the story they start to tell.
“After evolving for several thousand years in east Asia, a subgroup of dogs radiated out of southern East Asia about 15,000 years ago to the Middle East, Africa as well as Europe. One of these out-of-Asia lineages then migrated back to northern China and made a series of admixtures with endemic east Asian lineages, before travelling to the Americas,” the scientists say.
“Our study, for the first time, reveals the extraordinary journey that the domestic dog has travelled on this planet during the past 33,000 years.”
The grey wolf connection has been made before, along with the link with East Asia. The scientists, led by Guo-Dong Wang, a molecular biologist at the Kunming Institute of Zoology, have once more confirmed it. The indigenous Chinese dogs revealed closer links to their wolf ancestors, and retained the greatest genetic variety, another indicator that the domestic canine began somewhere in East Asia. The modern European specialist breeds showed less genetic diversity, suggesting that they descended from a subset of the first dogs, and the DNA of village dogs of Africa showed even less diversity, implying that they owed their origins to an even smaller set of migrant ancestors.
But the same genetic evidence suggests that at least some dogs from Europe and western Asia may have travelled back into China to interbreed, complicating the story. The ancestral dog and wolf may have continued to interbreed for a while, but the scientists are confident enough of their findings not only to put a date for the emergence of what became the domestic dog – around 33,000 years ago – but even to guess at an original or founder population of about 4,600 individuals.
Whether these joined forces with Ice Age human hunter gatherers, or whether they stayed as wild as the wolves, scavenging on human kills, and subsequently joined up with human companions as part of the civilisation package about 15,000 years ago on the journey to the west, is still uncertain.
“Our study, for the first time, begins to reveal a large and complex landscape upon which a cascade of positive selective sweeps occurred during the domestication of dogs,” the scientists write. “The domestic dog represents one of the most beautiful genetic sculptures shaped by nature and man.”
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