Paleoeconomy more than demography determined prehistoric human impact in Arctic Norway

Abstract

Population size has increasingly been taken as the driver of past human environmental impact worldwide, and particularly in the Arctic. However, sedimentary ancient DNA (sedaDNA), pollen and archaeological data show that over the last 12,000 years, paleoeconomy and culture determined human impacts on the terrestrial ecology of Arctic Norway. The large Mortensnes site complex (Ceavccageađgi, 70°N) has yielded the most comprehensive multiproxy record in the Arctic to date. The site saw occupation from the Pioneer period (c. 10,000 cal. years BP) with more intensive use from c. 4,200 to 2,000 cal. years BP and after 1,600 cal. years BP. Here, we combine on-site environmental archaeology with a near-site lake record of plant and animal sedaDNA. The rich animal sedaDNA data (42 taxa) and on-site faunal analyses reveal switches in human dietary composition from early-Holocene fish + marine mammals, to mixed marine + reindeer, then finally to marine + reindeer + domesticates (sheep, cattle, pigs), with highest reindeer concentrations in the last millennium. Archaeological evidence suggests these changes are not directly driven by climate or variation in population densities at the site or in the region, but rather are the result of changing socio-economic activities and culture, probably reflecting settlers' origins. This large settlement only had discernable effects on its hinterland in the last 3,600 years (grazing) and more markedly in the last 1,000 years through reindeer keeping/herding and, possibly domestic stock. Near-site sedaDNA can be linked to and validate the faunal record from archaeological excavations, demonstrating that environmental impacts can be assessed at a landscape scale.

Keywords: Arctic ecology; climate human impact; hunter–gatherers–fishers; sedimentary ancient DNA; sustainability.

Fig. 1.

Maps of the area and site. (a) The Arctic circle with principal ocean currents, areas of Arctic vegetation (dark yellow) from (34), and the best known early human colonization sites (various sources), (b) Varanger Fjord with the Mortnesness site area indicated (red rectangle), (c) the vegetation survey around Nordvivannet using types from the Norwegian Vegetation Classification system, and (d) the Mortensnes site complex plan with areas and house areas indicated (yellow dots). Data from Havsforskningsinstituttet (b), Google Earth https://earth.google.com/web/@70.129263,29.00124749,0.07289727a,7700.32164842d,35y,-0h,0t,0r, (c), site data from Kulturminnesøk on Lidar data from Høyedata (d), and from ref. (33) and a survey by Rijal in 2020 (33).

Fig. 2.

Nordvivatnet: selected XRF elements, LOI, sedaDNA-based plant functional groups based on proportion of reads divided into zones (N1 to N5a, b), and pollen proportion of functional groups divided into pollen assemblage zones (N_po1 to N_po6). Gray silhouettes are ×10. Note the variable scales (incl. ×10) and the high “synanthrope” (taxa associated with humans) values in the Early Holocene—see text for discussion. The vegetation zones with lower broken-stick support are indicated by double-dashed red lines. Graminoid in the pollen excludes Cyperaceae, which is shown separately.

Fig. 3.

(a) Detection of animal sedaDNA from 45 samples throughout the Nordvivatnet record with sedaDNA plant zones. Background colors delineate habitat categories. The taxa with a gray background could not be assigned to a habitat category, whereas those with a red background are assumed contaminants. Full taxonomic information is in Dataset S2 and Dataset S3. The same data plotted by depth and including the negative controls are in the Supplementary Material Appendix Fig. S5. Silhouette credits are in the Supplementary Material Appendix Text (c). M/FW: Marine/Freshwater. (b) Temporal trends of terrestrial plant species (a) composition and (b) richness, and pattern of (c) species composition along a proxy for climate (NGRIP δ18O) and pattern of both the (d) richness and (e) composition along a proxy for relative human population density. All the fitted lines are based on generalized additive models and colored envelopes represent 95% CIs of estimates.

Fig. 4.

(a) Barents Sea margin sea temperatures inferred from foraminifera from ref. (50) with typical Arctic fish (Arctic cod) and Atlantic fish (Atlantic cod). (b) The summary of faunal data from three houses, (c) the summary of faunal data from three houses at Mortensnes with their date ranges calculated from ref. (35) and Supplementary Material Appendix Table S1, (c) Mortensnes archaeology superimposed on the Varanger Fjord relative mean sea level curve (msl) from ref. (51) with the house height data from ref. (36) (gray circles) adjusted in age to fit with the msl curve (broken line) and a summary of key faunal data from Nordvivatnet and the SPD area curve from ref. (8) for northern Norway. The size of the reindeer icons reflects the number of sedaDNA repeats (0 to 4).