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Tuesday, May 24, 2011

Dog History

Beuty Of Animlas | Dog History  | Dog history is really the history of the partnership between dogs (Canis lupus familiaris) and humans. That partnership is based on human needs for help with herding and hunting, an early alarm system, and a source of food in addition to the companionship many of us today know and love. Dogs get companionship, protection and shelter, and a reliable food source out of the deal. But when this partnership first occurred is at the moment under some controversy.

Dog history has been studied recently using mitochondrial DNA, which suggests that wolves and dogs split into different species around 100,000 years ago; but whether humans had anything to do with that, no one really knows. Recent mtDNA analysis (Boyko et al.), suggests that the origin and location of dog domestication, long thought to be in east Asia, is in some doubt.

Dog History and Archaeological Data

The oldest dog skull discovered to date is from Goyet Cave, Belgium. The Goyet cave collections (the site was excavated in the mid-19th century) were examined recently (Germonpré and colleagues, cited below) and a fossil canid skull was discovered among them. Although there is some confusion as to which level the skull came from, it has been direct-dated by AMS at 31,700 BP. The skull most closely represents prehistoric dogs, rather than wolves. The study examining the Goyet cave also identified what appears to be prehistoric dogs at Chauvet Cave (~26,000 bp) and Mezhirich in the Ukraine (ca 15,000 years BP), among others.

However, I am told that what the Goyet Cave skull represents is not a "domesticated dog" but rather a wolf in transition to a dog, and that the physical changes seen in the skulls (consisting primarily of the shortening of the snout) may have been driven by changes in diet, rather than specific selection of traits by humans. That transition in diet could well have been partly due to the beginnings of a relationship between humans and dogs, although the relationship might have been as tenuous as animals following human hunters to scavenge, rather like the behavior that is believed to have existed between humans and cats. You could argue that cats never have been domesticated, they just take advantage of the mice we attract.

Evidence of a "Real" Domestication Partnership

A burial site in Germany called Bonn-Oberkassel has joint human and dog interments dated to 14,000 years ago. The earliest domesticated dog found in China is at the early Neolithic (7000-5800 BC) Jiahu site in Henan Province. European Mesolithic sites like Skateholm (5250-3700 BC) in Sweden have dog burials, proving the value of the furry beasts to hunter-gatherer settlements. Danger Cave in Utah is the earliest case of dog burial in the Americas, at about 11,000 years ago.

Dogs as Persons

A reanalysis (Losey et al. 2011 cited below) of dog burials dated to the Late Mesolithic-Early Neolithic Kitoi period in the Cis-Baikal region of Siberia suggests that in some cases, dogs were awarded "person-hood" and treated equal to fellow humans. A dog burial at the Shamanaka site was of a male, middle-aged dog (probably a husky) which had suffered injuries to its spine, injuries from which it recovered. The burial, radio-carbon dated to ~6200 years ago (cal BP), was interred in a formal cemetery, and in a similar manner to the humans within that cemetery. Losey and colleagues believe the dog may have lived with its human family at Shamanaka.

A wolf burial at the Lokomotiv-Raisovet cemetery (~7300 cal BP) was also an older adult male. The wolf's diet (from stable isotope analysis) was ungulates, and although its teeth were worn, there is no direct evidence that this wolf was part of the community. Nevertheless, it too was buried in a formal cemetery.

These burials are exceptions, but not that rare: there are others, but there is also is evidence that Kitoi culture consumed dogs and wolves, as their burned and fragmented bones appear in refuse pits. Losey and associates suggest that these are indications that Kitoi hunter-gatherers considered that at least these individual dogs were "persons".
Haplotypes and Grey Wolves

A recent study led by Robert Wayne (vonHoldt et al., below) at UCLA and appearing in Nature in March 2010 reported that dogs appear to have a higher proportion of wolf haplotypes from grey wolves native to the Middle East. That suggests, contrary to earlier studies, that the middle east was the original location of domestication. What also showed up in this report was evidence for either a second Asian domestication or a later admixture with Chinese wolves.

Dog History: When Were Dogs Domesticated?

It seems clear that dog domestication was a long process, which started far longer ago than was believed even as recently as 2008. Based on evidence from Goyet and Chauvet caves in Europe, the dog domestication process probably began as long ago as 30,000 years, although the oldest evidence for a broader relationship, a working relationship, is at the Bonn-Oberkassel site, 14,000 years ago. The story of dog domestication is still in transition itself.