When the first Americans arrived in theNew World at least 12,000 years ago, these hunter-gatherers brought domesticated dogs with them, UCLAevolutionary biologists and colleagues reported in the Nov. 22 issue of thejournal Science.
The international team of scientists used molecular genetictechniques to analyze mitochondrial DNA from ancient bones of dogs fromarchaeological sites across Latin America and Alaska pre-dating Columbus'journey to America.
A former graduate student in the lab of UCLA biology professorRobert K. Wayne, Jennifer A. Leonard — currently a postdoctoral fellow at theSmithsonian Institution's National Museum of Natural History — extracted DNAfrom bones of dogs from archaeological sites in Peru, Bolivia and Mexico, andcompared the DNA with DNA from modern dogs and modern wolves. Much of the DNA was well preserved, Leonardsaid.
The hunter-gatherers brought the dogs enormous distances, whichshows that the dogs were regarded as very valuable.
"Dogs are expensive traveling companions, who require food andcare," said Wayne, a co-author of the research. "They must have served animportant function in ancient societies, and have been thoroughly domesticatedto move great distances without wandering off into the countryside. We believethey were a fundamental part of ancient societies. Dogs may have been valuedfor their hunting skills, security, transport, warmth, perhaps even helpingearly travelers to move great distances.
"Dogs are the only domesticated animal that had a New World andOld World distribution before the arrival of Columbus to North America," Waynesaid.
"Our results show that ancient American dogs were more similar todogs from the Old World than to gray wolves of North America," Leonard said."This implies that when nomadic hunter-gatherers migrated across the BeringStrait from Asia into North America, at least
12–14,000 years ago, they already had dogs with them. Thediversity observed in the ancient American dogs indicates that multiplelineages of dogs were taken in to the New World."
What characteristics of dogs caused them to have such high valuein ancient societies and why were they domesticated thousands of years beforeother animals and plants? The answers to these questions are obscured by thelong unwritten history of dogs and by the dramatic difference between the roleof dogs in ancient and modern societies, Wayne said.
"Did dogs contribute to the rapid expansion of humans into the NewWorld?" Wayne asked. "At this point we can only speculate about the way dogschanged early human societies, but our new findings suggest that the effect mayhave been profound."
When did the association between humans and dogs begin? By the timehumans arrived in the New World, the diversity of dogs was already substantialand dogs were spread acrossEurasia, Wayne said.
"This suggests a very long coexistence of humans and dogs," Waynesaid. "Previous genetic analyses support this conclusion and have suggestedthat this association could have lasted tens of thousands of years. Dogs havebeen living in close association with humans much longer than any otherdomestic animal or plant species."
Although New and Old World dogs are descended from the same OldWorld wolf ancestor, the DNA sequences from ancient American dogs are slightlydifferent from their modern counterparts.
"Consequently, these data suggest Native American dogs have notgenetically contributed to modern dog breeds," Wayne said. "DNA sequences fromhundreds of dogs from dozens of modern breeds from throughout the world do notshow traces of American ancestry. Native dogs may still have living descendantsin some unsampled New World population, but their absence for a large sample ofmodern dogs reinforces the dramatic impact that the arrival of Europeans had onnative cultures."
The new molecular genetic analysis suggests that the majority ofthe living dog gene pool does not contain any ancestry from these long isolatedNative American dogs, Wayne said.
"This implies selective breeding, either intentional — whereEuropean colonists forcefully discouraged the breeding of native dogs, as theydid with other aspects of native culture — or dogs of European origin maysimply have been considered more desirable; both scenarios may have occurred indifferent regions. There was not wide-scale interbreeding of European andnative American dogs; native American breeds did not persist into the moderndog gene pool."
The scientists on the study also include evolutionary biologistCarles Vila from Uppsala University,Sweden, and zooarchaeologists from Mexico and Peru: Jane Wheeler, RaulValadez and Sonia Guillen.
Wayne's research was partially funded by the National ScienceFoundation.