By Holly Dickinson-Smith
Historically, it was assumed that the domestication of dogs took place in a single genetic divergence event around 15,000 years ago. Now, new research has found that domestication (in which gray wolves genetically diverged into dogs) could have originally taken place independently on two occasions in Eastern and Western Eurasia. These two populations later merged to eventually become the loyal mammals we know and love today.
A research team led by Anders Bergström recently gathered and sequenced ancient wolf genomes in Europe, Siberia, and North America. They then localized gene flow to detect wolf migration and breeding in specific regions of the world over the past 100,000 years. Results showed the possibility of two domestication events in separate locations, where admixing (interbreeding between these populations) was the basis for the rise of the dog lineage present today. These events would have taken place in Eastern and Western Eurasia, respectively, followed by admixture in southwestern Eurasia. Not only were dogs the only large carnivorous species to ever be domesticated, but they were also the first species to ever undergo this domestication.
Domestication is a process that can be defined in two ways. Whereas a scientific definition focuses on the divergence of wolves into dogs, anthropologists define it as the process of taming an animal for human companionship or use. Domestication created a symbiotic companionship between dog and hunter-gatherer for foraging. Humans received support in hunting and herding, while dogs received a reliable source of food, shelter, and protection.
The proximity of these isolated wolves to human contact contributed to inbreeding that led to the development of the characteristics associated with dogs today. With recent research proposing that this event could have taken place more than once, this implies that wolves were particularly susceptible to domestication. This makes sense considering their reputation for staying within a pack. But why, if wolves were cared for in packs, would they require an extra layer of care amongst humans? It is suggested that human care added an additional safety blanket, reduced energy consumption for finding meals, and provided the security for food sources that wolves in packs could not.
Althoughs have recently been made using genotyping techniques, there is substantial information still unknown about domestication due to complications in pinpointing the phylogenetic relationships between wolves and dogs. As the divergence of wolves into dogs took place over a short period, the evolutionary tree of each type of wolf and dog is difficult to organize and date. Also, since domestication took place, breeding continued between dog and wolf, further complicating this evolutionary tree through the creation of hybrid species. Ancient wolf genomes from outside the regions Europe, North America, Asia, Siberia, and Eurasia are necessary for further identification of the wolf lineage. However, studies such as Bergström’s are unable to utilize foreign DNA due to a lack of preservation.
While Bergström’s team confidently determined two independent domestication events were likely to have taken place to stimulate the wolves’ divergence into dogs, they also stipulated these results could have been produced due to individual domestication of wolves within eastern Eurasia, followed by admixture from western wolves later. where the dog genes became more prevalent in wolf DNA. This reveals the difficulty in analyzing DNA to organize the whereabouts and bloodline of these mammals, and how important well-preserved DNA is for proper analysis. As a result, scientists such as Bergström’s team are forced to make predictions on the evolution of wolves based on limited evidence.
Given that evidence has shown that in two regions wolves were domesticated before hybridisation, this research gives rise to a key question: if this process took place independently more than once, was the destiny of the wolf always to become a human companion, or was the basis of this due to humans’ successful survival rates, making being their companion the best mode of their own survival? Further research into the wolf diversification into dog could reveal more information about this, as well as the nature of humanity’s relationship to their ‘best friends.’
Image: Thomas Bonometti via Unsplash