GenomeWeb News – Dog domestication from a still-to-be-determined group of wild wolf ancestors likely occurred through a series of dynamic processes that began before the advent of widespread agriculture by humans, according to a new PLOS Genetics study.
“Dog domestication is more complex than we originally thought,” University of Chicago geneticist John Novembre said in a statement. “It makes the field of dog domestication very intriguing going forward.”
Novembre and University of California at Los Angeles researcher Robert Wayne led a group of researchers who did genome sequencing on gray wolves from China, Croatia, and Israel — geographical regions representing locales previously proposed as potential centers for dog domestication.
Golden Jackal (Canis aureus)
The team also sequenced an Australian Dingo and an indigenous Basenji dog, believed to represent breeds from the base of the domestic dog tree, as well as the genome of a golden jackal, which belongs to a canine lineage that diverged prior to the dog-wolf split.
By analyzing the newly sequenced genomes, together with existing wolf and dog data, the researchers found that domestic dogs tend to cluster more closely with one another than with wolves, forming a single phylogenetic group with an apparent history of mixing with wolves.
Somewhat unexpectedly, they estimated that that domestication event took place as far back as 34,000-years-ago, probably preceding the advent of widespread human agriculture. But from patterns in the genomes, the study’s authors argued that the source population of the domestic dog lineage was probably not any one of the wolf lineages currently found in the Middle East, Europe, or Asia.
“One possibility is there may have been other wolf lineages that these dogs diverged from that then went extinct,” Novembre said in a statement.
“So now when you ask which wolves are dogs most closely related to, it’s none of these three because these are wolves that diverged in the recent past,” he explained. “It’s something more ancient that isn’t well represented by today’s wolves.”
A male dingo
Novembre, Wayne, and their colleagues used SOLiD and Illumina HiSeq sequencing, to generate high-quality genome sequences for six canines: three gray wolves, a Basenji, a Dingo, and a golden jackal.
The wolves selected for the study came from Israel, China, and Croatia, making it possible to test several dog domestication theories, including the so-called “regional domestication” hypothesis, which suggests dogs became domesticated independently in different parts of the world.
Under the regional domestication scheme, for example, the Basenji (an African breed) is expected to share closer ancestry with wolves from Israel, while sequences from the Dingo and Boxer breed (used to generate the dog reference genome) would theoretically show genetic ties to wolves from China and Croatia, respectively.
In contrast, though, the researchers’ analysis of more than 10 million SNPs in the canine genomes indicated that domestic dogs cluster together in a group that’s genetically separate from the wolves, which form their own genetic cluster.
A red basenji with white markings
Such findings are consistent with a single dog phylogeny, the researchers noted, though none of the modern-day wolves tested for the study appear to be descendants of the domestic dog source population.
The sequences held signs of earlier-than-anticipated dog domestication, too. Whereas past studies have argued that dogs became cozy with human populations after a shift to more agricultural lifestyles, the new analysis hints that domesticated dogs may have been around back when a hunting and gathering lifestyle was still more widespread amongst humans.
In conjunction with the estimated timing of dog origins, these results provide additional support to archaeological finds,” researchers wrote, “suggesting the earliest dogs arose alongside hunter-gatherers rather than agriculturists.” Full Story On GenomeWeb News