Researchers analyzing the DNA of over 5,000 purebreds and mixed breeds alike say dogs were domesticated in Central Asia – likely near modern-day Nepal or Mongolia – and then they spread from there to East Asia and elsewhere. The findings are published in Proceedings of the National Academy of Sciences this week.
Archaeologists and geneticists agree that dogs evolved from Eurasian gray wolves at least 15,000 years ago. And while Canis lupus familiaris might be the world’s first domesticated species, exactly when and where that happened is still hotly debated.
Most of the dogs we have today aren’t actually purebred or even mixes of modern breeds. Rather, most are “village dogs” belonging to a free-ranging, free-breeding population with some relationship with humans. Village dogs are more genetically diverse and geographically widespread partly because bottlenecks and artificial selection have drastically skewed genetic diversity within breeds. That, in addition to their large population sizes, make village dogs a good reflection of the genetic structure of dogs from before modern times. And they can help supplement genetic analyses of ancient DNA to figure out where and where dog domestication occurred.
So, Cornell’s Adam Boyko and colleagues analyzed more than 185,800 genetic markers in blood samples taken from 4,676 purebred dogs (from 161 breeds), 167 mixed-breed dogs, and 549 village dogs from 38 countries. They focused on mitochondrial, Y chromosome and autosomal diversity. (Autosomes are chromosomes that aren’t the X or Y sex chromosomes.)
Both isolation and gene flow, the team found, shaped genetic diversity in dogs. Neotropical and South Pacific populations are almost exclusively descended from European stock, even though large dog populations lived in these regions before European contact. That suggests they were largely replaced by European dogs. Meanwhile, other dogs including those in Africa are the result of mixing between European and indigenous dogs.
Importantly, many populations – including those of Vietnam, India, and Egypt – show little evidence of European admixture. Instead, they exhibit a Central Asian domestication origin. Dogs in nearby East Asia and Southwest Asia show high levels of genetic diversity due to their proximity to Central Asia.
Gray wolves were present in the area during the Mesolithic, and they were exploiting large mammals at the same time as human hunter-gatherers. However, increasing human population density, combined with our hunting technology, may have altered prey numbers – forcing some wolves to become scavengers. Adaptations to scavenging, such as tameness and smaller body sizes, may have further reduced their hunting skills.