Researchers from Alaska and Washington state have found the earliest known evidence that Ice Age humans in North America used salmon as a food source, according to a paper published this week in the Proceedings of the National Academy of Sciences.

“Salmon fishing has deep roots, and we now know that salmon have been consumed by North American humans at least 11,500 years ago”, Carrin Halffman, lead author and a University of Alaska Fairbanks (UAF) anthropologist who helped analyze the fish bones, said in a news release.

Dr. Ben Potter, UAF professor of anthropology and project director at the Upward Sun River site, said the findings also have broader implications toward understanding the technology, economy and settlement patterns of early Alaskans.

The use of salmon at this early age suggests that humans in the area weren’t only big game hunters, as traditionally portrayed.

“We used ancient DNA analysis to identify the fish specimens as chum salmon (Oncorhynchus keta), and stable isotope analysis to confirm that the salmon were anadromous (sea-run), the researchers wrote in their study”.

Known as Beringians, the population reached North America from Siberia from land bridges that formed during Ice Ages.

The same site, as discovered by researchers at the University of Alaska Fairbanks, yielded animal bones and human bones. The Pleistocene ended 11,700 years ago. Fish bones are also often under-represented in the archaeological record because of the fragility of their skeletal elements and small size. Researchers said the two separate burial events suggest a longer-term residential occupation of the site than previously expected, and the presence of fish indicating they lived there between June and August.

But he said at the Upward Sun River site, the bones were backfilled into the hearth, leading to less exposure. Potter added that, “This suggests salmon fishing may have played a role in the early human colonization of North America”.

According to The New York Times, a team of researchers discovered salmon remains dating back about 11,500 years, but the fish were found in what was apparently a cooking hearth.

She said while there’s no direct evidence supporting such a theory, in Interior Alaska there were no significant barriers – such as ice blocking rivers – that would have blocked salmon from migrating during that time period.