Claire Alix

The transformation of the Birnirk culture into the Thule culture is essential in reconstructing the emergence of modern Inuit across Alaska and the larger Bering Strait. To this end, two adjacent semi-subterranean houses of late Birnirk and early Thule affiliation, respectively, at the Rising Whale (KTZ-304) site at Cape Espenberg were recently excavated and dated by radiocarbon and tree-ring measurements. We present the Bayesian analysis of the resulting large series of dates, demonstrating the lack of contemporaneity between the two features: the Birnirk house was occupied in the late twelfth to early thirteenth centuries AD, whereas the occupation of the Thule house occurred in the second half of the thirteenth into the early fourteenth century. With the increased precision made possible by coupling dendrochronology with radiocarbon, our results place the Birnirk-Thule transition more that 200 years later than the generally accepted date of AD 1000. A transition in the second half of the thirteenth century has major implications for the timing of Thule presence along the coast of Alaska and for their migration into the Alaska interior. It aligns with a thirteenth-century migration into the western Canadian Arctic and farther east and a brief early or “initial” Thule period.

Along the coast of northwestern Alaska, architectural wood remains are well preserved in the Birnirk and Thule coastal sites of the early 2nd millennium CE. These structural wood elements are unique archives for documenting climatic variations and cultural transformations during this key development period of Inuit culture. Along this treeless Arctic coast, driftwood accumulates from the subarctic forests of interior Alaska. Except for northwestern Alaska, regional tree-ring chronologies are too short (at best 350–400 years) to successfully date archaeological wood remains from Birnirk and Thule coastal sites using conventional dendrochronology. This paper examines the potential of tree-ring derived δ¹⁸O signal to annually date eight architectural wood samples from the Rising Whale (KTZ-304) site at Cape Espenberg, northwestern Alaska. We developed a δ¹⁸O master chronology, covering the period 935–1157 CE, using five wood samples from the KTZ-304 site. Blind isotope cross-dating of individual series belonging to this δ¹⁸O master chronology (one against the other four) showed conclusive dating and a very strong coherence of the isotopic signal. We, then, used the δ¹⁸O master chronology to cross-date three other wood samples for which we knew, from previous ¹⁴C wiggle-matching procedure, the first measured ring to be in this time interval, within a ± 18 to 30-year precision. Oxygen isotope dendrochronology provided a plausible date for one of the samples (the first measured ring at 1073 CE). This preliminary study encourages us to acquire additional data to extend in time and strengthen the δ¹⁸O master chronology of northwestern Alaska (NWAK_18O) and help refine our understanding of climate and culture change during the 2nd millennium CE.

Archaeological evidence indicates that Birnirk peoples (AD 650 – 1300) are the proposed genetic ancestors of the Thule Inuit (AD 950 – 1400) and are potentially an intermediary population between the Thule Inuit and earlier Old Bering Sea people (AD 1 – 1000). We sequenced the first hypervariable region of the mitochondrial DNA of 22 clearly associated Birnirk individuals from the Piġniq (Birnirk), Kugok, Kugusugaruk, and Nunavak sites on the North Slope of Alaska. Haplotypes A2a, A2a1, A2a3, A2b1, and D4b1a2a1a were identified in this population, demonstrating an expansion of Birnirk maternal genetic diversity. Maternal lineages from these individuals were evaluated with other past and contemporary Inuit populations from the Chukotka Peninsula to eastern Greenland. Our findings confirm Birnirk Inuit as probable maternal ancestors to Thule Inuit and may be among the first peoples possessing these lineages to have moved into the western North American Arctic from the Bering Strait region.