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Ancient bond between humans and dogs revealed in isotopic signatures of their bones

Analyzing the signatures of stable isotopes from bones is a new and important tool by which scientists are learning about the diets of people and animals that lived hundreds and even thousands of years ago. Now, stable isotope data is illuminating the strong bond that has existed between humans and dogs for millennia.

SRI-2 dog burial exposed on Santa Rosa Island, California. Research by Torben Rick, National Museum of Natural History anthropologist

Dog remains from a burial on Santa Rosa Island. (Photos courtesy Torben Rick)

In recent research on Santa Rosa Island off the coast of Southern California, isotope readings of carbon and nitrogen found in the bones of Chumash Indians and domestic dogs excavated from archaeological sites (dating from the Late Holocene–130AD-1830) show that both humans and dogs have nearly identical signatures of stable isotopes. The discovery illustrates that the Chumash and their dogs shared virtually the same diet of food from the sea—finfish, shellfish, marine mammals and sea birds. By contrast, isotope analysis of fox remains from the same period, also from Santa Rosa Island, shows the foxes ate a diet of terrestrial foods, such as insects and mice. The study was conducted by a scientific team led by Torben Rick of the Department of Anthropology at the Smithsonian’s National Museum of Natural History.

Image left: An island fox (Photo by Rene Vellanoweth, Cal State University Los Angeles)

An island fox (Photo by Rene Vellanoweth, Cal State University Los Angeles)

The data show that domestic dogs and humans were living in close proximity and the dogs were either fed scraps and leftovers from human meals, or they were scavenging in kitchen middens and refuse heaps and consuming human feces. The Santa Rosa Island findings confirm what archaeologists have discovered elsewhere in North America–that the isotopic signatures of the bones of humans and their dogs are extremely similar.

Torben Rick excavating an archaeological site on Santa Rosa Island.

In some situations where the destruction of human remains for isotope analysis is objectionable or banned, the researchers say, dog remains might easily be substituted for human remains to help reveal the diets of the humans. A paper on this research “Stable isotope analysis of dog, fox and human diets at a Late Holocene Chumash village on Santa Rosa Island, California,” was recently published in the Journal of Archaeological Science.

–John Barrat


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