Early human use of anadromous salmon in North America at 11,500 y ago Carrin M. Halffmana,1, Ben A. Pottera, Holly J. McKinneya, Bruce P. Finneyb, Antonia T. Rodriguesc, Dongya Y. Yangc, and Brian M. Kempd,e aDepartment of Anthropology, University of Alaska Fairbanks, Fairbanks, AK 99775; bDepartments of Biological Sciences and Geosciences, Idaho State University, Pocatello, ID 83209; cDepartment of Archaeology, Simon Fraser University, Burnaby, BC, Canada V5A 1S6; dDepartment of Anthropology, Washington State University, Pullman, WA 99164; and eSchool of Biological Sciences, Washington State University, Pullman, WA 99164 Edited by Eske Willerslev, University of Copenhagen, Copenhagen, Denmark, and approved August 19, 2015 (received for review May 18, 2015) Salmon represented a critical resource for prehistoric foragers contexts. This scarcity is related in part to the spawning habitat of along the North Pacific Rim, and continue to be economically and most salmon species, leading to death in river gravels where re- culturally important; however, the origins of salmon exploitation mains are unlikely to be preserved (9) and to the fragility of fish remain unresolved. Here we report 11,500-y-old salmon associated skeletal elements and their small size (inhibiting recovery), resulting with a cooking hearth and human burials from the Upward Sun in their underrepresentation in the archaeological record (10). Pa- River Site, near the modern extreme edge of salmon habitat in leontological specimens of Pacific salmon have been recovered from central Alaska. This represents the earliest known human use of middle Pleistocene sediments in the Skokomish Valley, Washington salmon in North America. Ancient DNA analyses establish the (United States) (9), and from late Pleistocene sediments at Kam- species as Oncorhynchus keta (chum salmon), and stable isotope loops Lake, British Columbia (Canada) (11). Although the remains analyses indicate anadromy, suggesting that salmon runs were from both of these locales were morphologically identified as established by at least the terminal Pleistocene. The early use of O. nerka, carbon stable isotope analysis of specimens from Kamloops this resource has important implications for Paleoindian land use, Lake suggests that the fish were likely the landlocked form of economy, and expansions into northwest North America. O. nerka, known as kokanee (11). Other late Pleistocene paleonto- logical fish remains assigned to Pacific salmon derive from two ad- salmon | Paleoindians | Beringia | ancient DNA | stable isotopes ditional sites in British Columbia, including Courtenay (Vancouver ANTHROPOLOGY Island) and Gaadu Din 1 cave (Haida Gwaii) (12, 13). Specimens ach year along the Pacific coast of North America, millions of from the latter site were genetically identified as “salmon,” but the Esalmon migrate from the ocean to spawn and die in their details of the aDNA analysis were not reported (13). natal rivers and lakes; however, during the last Ice Age, many of The only report of Oncorhynchus remains from a Pleistocene-age the rivers that today support salmon were blocked by glacial ice, archaeological site in North America comes from Upward Sun severely restricting salmon ranges (1). A potential glacial refugium River, located adjacent to the Tanana River (a major tributary of for salmon was Beringia, the mostly ice-free landmass that bridged the Yukon River) in central Alaska (14) (see also SI Text)(Fig.1). northeast Asia and Alaska (1–3). Evidence for such a refugium Here, 308 Oncorhynchus specimens were recovered from the central comes from studies of present-day diversity and distributions of hearth of a residential feature, also associated with a cremated Pacific salmon (1, 2), but there is little direct evidence of the an- 3-y-old child (15). A double infant burial with associated grave goods tiquity of salmon spawning runs in North America. Here we con- was located directly below (40 cm) this hearth. Radiocarbon and firm the presence of an anadromous salmon species, Oncorhynchus contextual data suggest near contemporaneity between the hearth keta (chum salmon) through ancient DNA (aDNA) and stable isotope analyses of fish remains at the Upward Sun River site lo- Significance cated deep in the interior of Alaska, about 50 km downstream from the modern limit of major spawning areas (Fig. 1). These speci- Fish bones from the 11,500-y-old Upward Sun River site in interior mens, dating to the terminal Pleistocene, represent the oldest ge- Alaska represent the oldest evidence for salmon fishing in North netically confirmed Pacific salmon species in an archaeological America. We used ancient DNA analysis to identify the fish context in North America. These data are important for testing specimens as chum salmon (Oncorhynchus keta), and stable iso- competing models of subsistence strategies and diet breadths of tope analysis to confirm that the salmon were anadromous (sea- Paleoindian populations in the New World (4, 5), as well as for run). The exploitation of salmon at this early date is noteworthy understanding Beringian ecosystem biodiversity. because Paleoindians are traditionally portrayed as big-game Oncorhynchus is a salmonid genus that includes several Pacific hunting specialists. Furthermore, the presence of salmon at Up- salmon and Pacific trout species; some species of this genus occur ward Sun River over 1,400 km upriver from the coast shows that as both freshwater resident and anadromous forms, migrating from spawning runs had been established by the end of the last Ice the sea to freshwater to spawn (6). The spawning behavior of Age. The early availability and use of anadromous salmon has anadromous Pacific salmon results in massive and predictable runs important implications for understanding Paleoindian economies in freshwater streams over a short period, making these fish a and expansion into North America. potentially valuable human food resource (7). Salmon are also ecologically important because they transport rich marine-derived Author contributions: C.M.H., B.A.P., and B.M.K. designed research; C.M.H., B.A.P., H.J.M., B.P.F., A.T.R., D.Y.Y., and B.M.K. performed research; C.M.H., B.A.P., H.J.M., B.P.F., A.T.R., nutrients into relatively unproductive interior riparian areas (8). D.Y.Y., and B.M.K. analyzed data; and C.M.H., B.A.P., H.J.M., B.P.F., A.T.R., D.Y.Y., and B.M.K. Five species of Pacific salmon and one species of Pacific trout wrote the paper. presently occur in central Alaskan waters, including Chinook The authors declare no conflict of interest. (Oncorhynchus tshawytscha), coho (Oncorhynchus kisutch), chum This article is a PNAS Direct Submission. (O. keta), sockeye (Oncorhynchus nerka), pink salmon (Onco- Data deposition: The sequences reported in this paper have been deposited in the Gen- rhynchus gorbuscha), and rainbow/steelhead trout (Oncorhynchus Bank database (accession nos. KT693031, KT693032, KT725810, and KT725811). mykiss)(1). 1To whom correspondence should be addressed. Email: [email protected]. Pleistocene-aged remains of Pacific salmon from North America This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. are extremely rare in both paleontological and archaeological 1073/pnas.1509747112/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1509747112 PNAS Early Edition | 1of5 Downloaded by guest on September 30, 2021 To address the questions of taxonomic identification and life history of the Upward Sun River Oncorhynchus specimens, we subjected two unburned vertebral specimens (58-18 and 58-30) to aDNA analysis, one of which (58-18) was also subjected to carbon and nitrogen stable isotope analysis (SI Text and Table S1). An unsuccessful attempt was also made to analyze DNA from a third specimen (H-5446), a nearly complete but calcined vertebra. The three specimens shared the distinctive morpho- logical and overall size characteristics of the larger number of burned and fragmented Oncorhynchus specimens. Results and Discussion DNA was extracted from the specimens following established methods (SI Text). The extracts for the unburned specimens were successfully PCR-amplified and sequenced for a region of the mitochondrial 12S gene that is useful for discriminating among Pacific salmonids and other fishes (31) (SI Text). Repeated se- quence analysis demonstrated the samples to be Oncorhynchus keta (chum salmon) (Table S2). Additionally, one sample (58-18) was analyzed at an independent aDNA laboratory using discriminating fragments of the d-loop and cytochrome b regions of the salmonid mitochondrial genome (22), confirming the identification made with 12S (SI Text, Figs. S2–S4,andTable S3). Thus, repeatable and independent analyses of mitochondrial DNA (mtDNA) demon- Fig. 1. Location of Upward Sun River Site, course of the Tanana-Yukon strate that both samples are chum salmon. River and possible course across the Bering Shelf during lower sea level, and Stable isotope analysis of bone collagen extracted from one of modern chum salmon fall spawning limit along the Tanana River. Details are δ13 δ15 provided in SI Text. the confirmed O. keta vertebra produced Cand N values of −15.1‰ and 12.6‰, respectively (SI Text). These values are consistent with previously reported isotope values for ancient and and the burial pit, with a mean pooled age of 9,970 ± 30 B.P. modern salmon from Alaska, and are elevated over those for (11,600–11,270 cal B.P.); thus, these represent the oldest known ancient and modern freshwater fishes (Fig. 3 and Tables S4 and human remains in the North American Arctic/Subarctic (Fig. 2 and S5). These data indicate that the Upward Sun River chum salmon SI Text). A total of 29 additional Oncorhynchus specimens were specimen was anadromous. found within the pit fill. The fish remains were mostly fragmentary The confirmed presence of an anadromous Pacific salmon spe- and over 90% were burned and calcined. The component and cies, O. keta, at the terminal Pleistocene Upward Sun River site burials are culturally affiliated with the Denali Complex, which was provides the earliest evidence for human use of salmon in North widespread in Eastern Beringia from ∼12,700 cal B.P.