May 22, 2012
Cross-breeding Has Muddled Genetic Link Between Modern And Ancient Dogs
Brett Smith for RedOrbit.com
The breeding of domestic dogs over thousands of years has made it extremely difficult to trace the genetic roots of man´s best friend, according to a new study led by researchers at Durham University in the U.K.
The research team set out to trace the origins of canine domestication, hoping to find a genetic link back to those animals pictured on the walls of Egyptian tombs or Roman ruins. Unfortunately, the genetic pool has been so muddled that they were unable to properly identify an “ancient” breed, according to their report published in the Proceedings of the National Academy of Sciences USA (PNAS).
"We really love our dogs and they have accompanied us across every continent,” said Greger Larson, an evolutionary biologist in Durham University's Department of Archaeology. "Ironically, the ubiquity of dogs combined with their deep history has obscured their origins and made it difficult for us to know how dogs became man's best friend.”
Scientists from a number of organizations including Uppsala University in Sweden and the Broad Institute in the U.S. analyzed genetic data from 1,375 dogs representing 35 breeds. They also looked at data culled from the genetic samples of wolves, as recent genetic studies have suggested that dogs are exclusively descended from the grey wolf.
After combing through the genetic data, researchers determined that previously thought "ancient" breeds such as the Akita, Afghan Hound and Chinese Shar-Pei, are no closer to the first domestic dogs than any other breeds due to the effects of cross-breeding. They did find that six breeds, the Basenji, Shar-Pei, Saluki, Akita, Finnish Spitz, and Eurasier, were less genetically mixed than others.
The study also suggested that the history of dog domestication is extremely short in comparison with the history of civilization, with humans keeping dogs as pets for about 2,000 years. The vast majority of these dogs were originally bred to do specific jobs.
“Both the appearance and behavior of modern breeds would be deeply strange to our ancestors who lived just a few hundred years ago,” Larson said. “And so far, anyway, studying modern breeds hasn't yet allowed us to understand how, where and when dogs and humans first started this wonderful relationship.”
Scientists indicated that they are currently pursuing genetic information within the canine fossil record, but this avenue is not without its pitfalls. The first major problem is that it is difficult to accurately discriminate between the earliest domesticated dog fossils and those of wolves or other similar wild animals. Modern wolves exist in pockets around the world but thousands of years ago they inhabited the entire Northern Hemisphere.
Other problems with analyzing the fossil record include taxonomic issues with vertebrate and complications associated radioactive dating of the bones.
In concluding their report, the researchers noted that the advent of rapid and inexpensive DNA sequencing technology would only deepen their understanding of the story of dog domestication. They said such technology has allowed geneticists to uncover history of human interspecies breeding and expect to do the same with man´s furry counterpart.