Salmon, aquatic animals and even dogs part of ancient human diets, archaeological evidence shows

Ancient people in Alaska regularly ate salmon, just as their dogs did — and sometimes the dogs wound up on the menu, new archaeological evidence shows.

Studies of two sites separated by thousands of years and hundreds of miles show that salmon were a part of the diet, sometimes an important part.

The famous Upward Sun River site in Interior Alaska has yielded evidence that salmon consumption in the ice age was a lot more common in that part of Alaska than previously believed.

Isotope analysis of charred samples from several fire pits that date back to 11,800 years ago contains residue of salmon oil, according to a new study published in Proceedings of the National Academy of Sciences.

The discovery comes from analyses by University of Alaska Fairbanks scientists of 17 ancient hearths at the Upward Sun River archaeological site. The site, near the confluence of the Tanana and Little Delta rivers, has already produced other important discoveries — burial sites for two infants and a young child who showed a surprising genetic diversity, along with evidence of ancient salmon consumption that dated back to 11,500 years.

What sets the new findings apart from a previous discovery showing evidence of the earliest known North American salmon fishing, said one of the scientists involved in both studies, is the recurrent nature of the salmon use — signs of salmon at multiple sites in different periods of time.

The discovery announced last year, identifying the food source as chum salmon, might have indicated only limited consumption of the fish, said Ben Potter of UAF's Department of Anthropology. "That could be an opportunistic thing — they caught one and they ate it and that was that," said Potter, a co-author of both studies and a specialist in Arctic and sub-Arctic archaeology.

The new discoveries, in addition to showing even earlier use of salmon, is evidence of much more reliance on the salmon that are still pulled from the Tanana River, he said.

"The fact that we've found people recurrently using salmon at multiple areas in multiple occupations suggests to me it was important enough to be reflected in their mobility and their movements," he said.

A separate site, the permafrost-preserved Nunalleq site in Southwest Alaska, has produced evidence of a salmon-heavy diet for both people and dogs. The site dates to a period before European contact, the years 1300 to 1750, and holds signs of an "abundance" of dogs kept by the Yup'ik people who lived there.

The study, published online in the Journal of Archaeological Science: Reports, analyzed dog fur and claw remains. Stable isotope analysis found a heavy reliance on salmon, with short-term use of marine-mammal meat. That matches results from human hair found at the same site, the study said.

The dog remains also show signs of butchery, "suggesting that they were processed for meat," the study says.

Dogs were the only domesticated animals kept by the Yup'ik people of that era, and they occupied  a position between the domestic and wild worlds, the study said.

"The fate of dogs was probably a delicate balance between their usefulness for transportation and hunting and the nutritional demands they put on the community," the study said.

For the ice age site at Upward Sun River, the key evidence showing that the ancient dwellers ate salmon is in the chemical fingerprint of the charred residue, which held a sign of the sea. The Upward Sun River site is at least 200 miles from saltwater, but salmon are anadromous — swimming from ocean to rivers, streams and lakes.

There is evidence from the hearths of even earlier use of aquatic-based food sources. Isotope analysis of samples dating back to 13,200 years ago showed a freshwater source — indicating freshwater fish or birds like ducks and geese, the study said.

The methodology itself was an important breakthrough in the new study, Potter said.

Up to now, archaeologists have relied on bones or analysis of pottery to reconstruct ancient diets, he said. But bones, especially fish bones, can be fragile and disappear over the millennia — or disappear in uneven patterns, leaving an incomplete picture of food sources. And many ancient peoples, including the Upper Sun River inhabitants, lacked pottery, he said. The analysis of hearth samples allows scientists to work around such limitations, he said.

The more modern Nunalleq site, subject of an ongoing program conducted by scientists from University of Aberdeen in Scotland, offers another way to reconstruct ancient diets. Dogs, the study concludes, can be good proxies for humans in high-latitude regions.