Science News reports recent analysis proves dogs have lived with humans in North America longer than previously supposed and that the genetics of some dogs kept by early inhabitants of North America have not survived to the present day.

A trio of dogs buried at two ancient human sites in Illinois lived around 10,000 years ago, making them the oldest known domesticated canines in the Americas.

Radiocarbon dating of the dogs’ bones shows they were 1,500 years older than thought, zooarchaeologist Angela Perri said April 13 at the annual meeting of the Society for American Archaeology. The previous age estimate was based on a radiocarbon analysis of burned wood found in one of the animals’ graves. Until now, nearly 9,300-year-old remains of dogs eaten by humans at a Texas site were the oldest physical evidence of American canines.

Ancient dogs at the Midwestern locations also represent the oldest known burials of individual dogs in the world, said Perri, of Durham University in England. A dog buried at Germany’s Bonn-Oberkassel site around 14,000 years ago was included in a two-person grave. Placement of the Americas dogs in their own graves indicates that these animals were held in high regard by ancient people.

An absence of stone tool incisions on the three ancient dogs’ skeletons indicates that they were not killed by people, but died of natural causes before being buried, Perri said. …

She and her colleagues studied two of three dogs excavated at the Koster site in the 1970s and a dog unearthed at Stilwell II in 1960. These sites lie about 30 kilometers apart in west-central Illinois.

Perri’s team found that the lower jaws and teeth of the Stilwell II dog and one Koster dog displayed some similarities to those of modern wolves. Another Koster dog’s jaw shared some traits with present-day coyotes, possibly reflecting some ancient interbreeding.

A new genetic analysis positions the 10,000-year-old Illinois dogs in a single lineage that initially populated North America. Dog origins are controversial, but may date to more than 20,000 years ago (SN Online: 7/18/17). Ancient American dogs, including the Koster and Stilwell II animals, shared a common genetic ancestor, cell biologist Kelsey Witt Dillon of the University of California, Merced reported April 13 at the SAA meeting. That ancestor originated roughly 15,000 years ago after diverging from a closely related Siberian dog population about 1,000 years earlier, she said.

Dillon’s team, which includes Perri, studied 71 complete mitochondrial genomes and seven nuclear genomes of dogs from more than 20 North American sites, ranging in age from 10,000 to 800 years ago. Mitochondrial DNA is typically inherited from the mother, whereas nuclear DNA comes from both parents.

Much of the genetic blueprint of those ancient dogs is absent in present-day canines, Dillon said. Only a small number of U.S. and Asian dogs share maternal ancestry with ancient American dogs, suggesting the arrival of European breeds starting at least several hundred years ago reshaped dog DNA in the Americas, she proposed.

RTWT