The human colonization of Beringia during the Late Glacial (14,500-11,700 years ago) is one of the most remarkable events in human history, as people coming from northeastern Eurasia permanently settled the subarctic for the first time and opened the way for the initial colonization of the New World, coincident with the extinction of mammalian megafauna. This dissertation uses an interdisciplinary methodological and theoretical framework to investigate the trophic ecology of past Beringian hunter-gatherers, their place in predator guilds and in the broader mammal community. Methods of study include faunal and spatial analyses of existing archaeological collections, analyzing the function of the sites as well as their spatial relationship to resources, and documenting new sites in the region through excavations. In support of the archaeological work I conducted isotopic analyses (δ13C and δ15N) of fossil megafauna from contemporaneous paleontological and archaeological sites in order to study habitat partitioning within the herbivore and predator guilds. Results show that resources targeted by early Beringian people were concentrated in high biomass patches and that people exploited these patches through highly specialized, logistical sites. Specifically, the occupation at Swan Point CZ4b is interpreted as a specialized workshop dedicated to the production and maintenance of organic-based tools, providing evidence that Beringian people relied on animals not only for food but also to a large extent for technological purposes. Isotopic data suggest that Beringian people are unlikely to have had profound negative effects on populations of large herbivores through their economic choices. On the other hand, humans do seem to have contributed to the extinction of Beringian large carnivores by competing with and ultimately displacing them at high trophic levels. This dissertation provides new evidence of the impact that the integration of early Beringian people within predator communities had on material culture and economy as well as on larger-scale ecosystem processes.

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Le climat continental et froid de la Béringie lors de la glaciation du Wisconsinien a conduit à la formation d’une forme relique de pergélisol syngénétique nommé yedoma. Ces dépôts ont permis la préservation d’indicateurs environnementaux très diversifiés qui peuvent être employés pour reconstituer la dynamique climatique et écologique de la Béringie avant le dernier maximum glaciaire. À ce jour, peu d’études ont été réalisées au nord de la chaîne de montagnes Brooks (Alaska) et l’hétérogénéité écologique régionale de la Béringie Est lors de la glaciation du Wisonsinien reste mal définie. Ce mémoire porte sur une reconstitution paléoenvironnementale de plus de 39 ka du nord de l’Alaska réalisée à partir de sédiments provenant du Yedoma de la rivière Itkillik. Les objectifs sont (1) de reconstituer l’histoire de la végétation avec l’analyse pollinique; (2) de reconstituer les températures de juillet, le contraste de température saisonnier et l’ensoleillement de juillet avec la technique des analogues modernes et (3) de mettre les données biogéochimiques et glaciologiques du site en lien avec le climat reconstitué. L’étude montre que vers 35 ka BP (Interstade du Wisconsinien Moyen), des conditions climatiques semblables à l’actuel ont favorisé l’accumulation de tourbe riche en carbone organique. À partir de 29,7 ka BP, les températures de juillet reconstituées diminuent, alors que la continentalité du climat semble augmenter. Le contenu en glace des sédiments est plus alors plus faible et la pluie pollinique devient dominée par Poaceae, Artemisia et autres herbacés non graminoïdes. Ces indicateurs suggèrent des conditions environnementales plus xériques qu’aujourd’hui. Les anomalies isotopiques de 18O, 2H et l’excès de deutérium confirment un épisode d’avancée glaciaire (Wisconsinien Tardif). Après 17,9 ka BP (Tardiglaciaire), les températures de juillet et le contraste saisonnier augmentent. Les valeurs de contenu en carbone organique des sédiments sont plus élevées et la plus grande disponibilité en eau favorise l’établissement d’un couvert herbacé moderne dominé par les Cyperaceae. / The cold-arid climate associated with the Wisconsinan glaciation in Beringia has led to the formation of a relict form of syngenetic permafrost, termed yedoma. These deposits contain various environmental proxies that can be used to reconstruct the climatic and ecological dynamics across Beringia prior to the Last Glacial Maximum (LGM). To date, only a few studies have attempted to reconstruct LGM climate north of the Brooks Range and the regional ecological heterogeneity of eastern Beringia is still poorly understood. The present thesis focuses on paleoenvironmental reconstructions of northern Alaska spanning about 39 ka, based on sediments from the Itkillik river Yedoma. The objectives are (1) to reconstruct the regional vegetation history from pollen analysis; (2) to reconstruct the July temperatures, seasonal temperature contrast and July sunshine based on the modern analogue technique applied to pollen and (3) to link the biogeochemical and glaciological records to the reconstructed climate. The study shows that around 35 ka BP (Middle Wisconsinan), climate conditions were similar than modern and favored the accumulation of peat and organic carbon. From 29.7 ka BP, July temperature decreased as continentality increased. Ice content was low and the vegetation was dominated by Poaceae, Artemisia and other non-graminoid indicators of xeric environmental conditions. Isotopic anomalies of 18O, 2H and deuterium excess indicate a glacial advance (Late Wisconsinan). Improving climate and ecological conditions is recorded after 17.9 ka BP (Late Glacial). Overall, the results are more similar to reconstructions of other sites located in northern and interior Alaska than those from interior Yukon or western Beringia.

The concept of biodiversity – the phenotypic and genotypic variation among organisms – is central to conservation biology. There is growing recognition that biodiversity does not exist in isolation, but rather is intrinsically and evolutionarily linked to cultural diversity and indigenous knowledge systems. In Canada, caribou (Rangifer tarandus) occupy a central place in the livelihoods and identities of indigenous people and display substantial variation across their distribution. However, quantifying caribou intraspecific variation has proven challenging. Interdisciplinary approaches are necessary to produce effective species characterizations and conservation strategies that acknowledge the interdependent relationships between people and nature in complex social-ecological systems. In this dissertation I use multiple disciplinary traditions to develop comprehensive and united representations of caribou variation through an exploration of population genetics, phylogenetics, traditional knowledge, language, and visual approaches in the Sahtú region of the Northwest Territories, Canada. First, I examine caribou variation through analysis of population genetics and the relationships Dene and Métis people establish with animals within bioculturally diverse systems. Next, I focus on how the Pleistocene glacial-interglacial cycles have shaped the current patterns of caribou phylogeographic lineage diversification. Finally, I explore how art can be used to facilitate cross-cultural collaboration and externalize the unique heterogeneity of biocultural diversity. The results demonstrate a broad scale understanding of the distribution, spatial organization, and the degree of differentiation of caribou populations in the region. I found evidence for caribou population differentiation that corresponds to the caribou types recognized by Dene people: tǫdzı “boreal woodland caribou,” ɂekwę́ “barren-ground caribou,” and shúhta ɂepę́ “mountain caribou.” Phylogenetic results reveal that in their northern margin the boreal ecotype of woodland caribou evolved independently from the northern Beringian lineage in contrast with southern boreal caribou which belong to the sub-Laurentide refugia lineage. In addition, I demonstrate how art can be used improve communication, participation, and knowledge production among interdisciplinary research collaborations and across language and knowledge systems. A collaborative process of research that facilitates łeghágots'enetę “learning together” has the potential to produce sustainable conservation solutions, develop efficient and effective wildlife management policies, and ensure caribou remain an important part of the landscape. / February 2017

La Béringie, un vaste territoire qui s’étend de la Sibérie orientale au Territoire du Yukon, est perçue comme le point d’entrée des populations humaines en Amérique. A la fin du Pléistocène, ce territoire déglacé aurait constitué un refuge aux premières populations préhistoriques se dispersant hors d’Asie. Selon les données génétiques et paléo-génétiques, la Béringie fut occupée au cours du Dernier Maximum Glaciaire (19 000-23 000 cal BP, années calibrées Before Present) par une population humaine qui demeura génétiquement isolée durant près de 8000 à 9000 ans, donnant ainsi naissance à la lignée des Natifs Américains qui allaient se disperser, plus tard, au sud des masses glaciaires nordaméricaines et jusqu’en Amérique du Sud. Cette « Beringian standstill hypothesis », toutefois, ne trouva aucun soutien dans le registre archéologique : en Sibérie orientale, le plus ancien site est daté à 32 000 cal BP, tandis qu’en Alaska et au Yukon, la présence humaine ne remonte pas au-delà de 14 000 cal BP. Dans les années 70-80’s, le site des Grottes du Poisson-Bleu (Yukon) livra des outils en pierre et des ossements supposés modifiés par les humains, enfouis dans un dépôt loessique pléistocène ; les découvertes encouragèrent les archéologues J. Cinq-Mars et R. Morlan à évoquer l’hypothèse d’une occupation humaine sporadique dans le nord du Yukon entre 11 000 et 30 000 cal BP environ. La nature anthropogénique des échantillons osseux soumis aux datations radiocarbones ainsi que l’intégrité de la stratigraphie furent toutefois remises en question par une majorité d’archéologues. La présente dissertation propose une analyse archéozoologique et taphonomique rigoureuse et systématique des assemblages fauniques de mammifères des Grottes I et II dans le but d’appréhender les facteurs responsables de l’accumulation et de la modification du matériel osseux. De nouvelles datations radiocarbones effectuées par le laboratoire Oxford Radiocarbon Accelerator Unit sur des ossements portant des traces indéniablement culturelles permettent une datation précise de l’occupation humaine du site. Les résultats illustrent plusieurs traces de découpe sur des os de cheval, caribou, wapiti et possiblement bison et mouflon, tandis que des ossements de mammouth pourraient avoir été collectés pour l’industrie osseuse. Les nouvelles datations AMS suggèrent que les Grottes du Poisson-Bleu étaient occupées de façon sporadique entre 12 000 et 24 000 cal BP, soit pendant et après le Dernier Maximum Glaciaire. Le site offre ainsi un soutien archéologique à l’hypothèse de l’isolation génétique des populations béringiennes à l’origine des premières dispersions en Amérique. L’histoire taphonomique des Grottes du Poisson-Bleu rejoint celle des sites karstiques béringiens qui illustrent des occupations interspécifiques alternées entre carnivores et des fréquentations humaines de courte durée pour des activités de chasse. En outre, les altérations anthropiques sur des os de cheval des Grottes I et II ravivent le débat sur les extinctions de la mégafaune à la fin du Pléistocène (ca. 14 000 cal BP). Le site souligne l’incomplétude du registre archéologique et invite à multiplier les efforts de recherche en Béringie si l’on veut être à même de comprendre la préhistoire du peuplement des Amériques. / Beringia, a vast landscape stretching from eastern Siberia to the Yukon Territory, is thought to be the initial entry point of humans into North and South America. At the end of the Pleistocene, this unglaciated region constituted a refugium for the first prehistoric populations dispersing out of Asia. According to genetic and palaeogenetic data, Beringia was occupied during the Last Glacial Maximum (19 000-23 000 cal BP, calibrated years before present) by a human population that remained genetically isolated for about 8000 to 9000 years, leading to the divergence of the Native American lineage that would eventually disperse south of the ice-sheets into North and South America. The « Beringian standstill hypothesis » is not well supported in the archaeological record, however: in eastern Siberia, the oldest archaeological site is dated to 32 000 cal BP while in Alaska and the Yukon, evidence for a human presence doesn’t exceed 14 000 cal BP. Excavated in the 70s-80s, the Bluefish Caves site (Yukon) yielded stone tools and bone remains thought to have been culturally modified, buried in a Pleistocene loess deposit; the discovery encouraged archaeologists J. Cinq-Mars and R. Morlan to propose that humans occupied the caves sporadically between about 11 000 and 30 000 cal BP. The anthropogenic nature of the bone samples submitted for radiocarbon analysis and the stratigraphic integrity of the site didn’t convince the scientific community, however. The current dissertation proposes a rigorous archaeozoological and taphonomic analysis of the mammal bone assemblages of Caves I and II in order to identify the agents responsible for the accumulation and modification of the bone material. The results show several cut marks on bone specimens belonging to horse, caribou, wapiti and possibly bison and Dall sheep, while mammoth skeletal remains may have been collected for bone industry. New radiocarbon dates obtained by an Oxford laboratory (Oxford Radiocarbon Accelerator Unit) on bone bearing indisputable evidence of cultural modification allow the precise dating of the human occupation at the site. The AMS dates suggest that the Bluefish Caves were occupied sporadically between 12 000 to 24 000 cal BP, i.e., during and after the Last Glacial Maximum. The site, therefore, offers archaeological support for the Beringian standstill hypothesis. The taphonomic history of the Bluefish Caves, as well as other Beringian karstic sites, shows use of the caves by various carnivores and short-term human occupations for hunting activities. Moreover, cultural modifications on horse bone from Caves I and II enhance the debate surrounding the megafaunal extinctions at the end of the Pleistocene (ca. 14 000 cal BP). The site underlines the incompleteness of the archaeological record and invites us to expand research efforts in Beringia if we are to understand the prehistory of the first people of the Americas.

Humans evolved in a world of giant creatures. Current evidence suggests that most ice age megafauna went extinct around the transition to our current Holocene epoch. The ecological reverberations associated with the loss of over 65% of Earth’s largest terrestrial animals transformed ecosystems and human lifeways forever thereafter. However, there is still substantial debate as to the cause of this mass extinction. Evidence variously supports climate change and anthropogenic factors as primary drivers in the restructuring of the terrestrial biosphere. Much of the ongoing debate is driven by the insufficient resolution accessible via macro-remains. To help fill in the gaps in our understandings of the Pleistocene-Holocene transition, I utilized the growing power of sedimentary ancient DNA (sedaDNA) to reconstruct shifting signals of plants and animals in central Yukon. To date, sedaDNA has typically been analyzed by amplifying small, taxonomically informative regions. However, this approach is not ideally suited to the degraded characteristics of sedaDNA and ignores most of the potential data. Means of isolating sedaDNA have also suffered from the use of overly aggressive purification techniques resulting in substantial loss. To address these limitations, I first experimentally developed a novel means of releasing and isolating sedaDNA. Secondly, I developed a novel environmental bait-set designed to simultaneously capture DNA informative of macro-scale ecosystems. When combined, we identify a substantial improvement in the quantity and breadth of biomolecules recovered. These optimizations facilitated the unexpected discovery of horse and mammoth surviving thousands of years after their supposed extirpation. I followed up these results by extracting DNA from multiple permafrost cores where we confirm the late survival signal and identify a far more complex and high-resolution dataset beyond those identifiable by complementary methods. I was also able to reconstruct mitochondrial genomes from multiple megafauna simultaneously solely from sediment, demonstrating the information potential of sedaDNA. / Dissertation / Doctor of Philosophy (PhD) / A new addition to the rapidly growing field of palaeogenetics is environmental DNA (eDNA) with its immense wealth of biomolecules preserved over millennia outside of biological tissues. Organisms are constantly shedding cells, and while most of this DNA is metabolized or otherwise degraded, some small fraction is preserved through sedimentary mineral-binding. I experimentally developed new ancient eDNA methods for recovery, isolation, and analysis to maximize our access to these biomolecules and demonstrate that this novel approach outperforms alternative protocols. Thereafter, I used these methods to extract DNA from ice age permafrost samples dating between 30,000–6,000 years before present. These data demonstrate the power of ancient eDNA for reconstructing ecosystem change through time, as well as identifying evidence for the Holocene survival of caballine horse and woolly mammoth in continental North America. This late persistence of Pleistocene fauna has implications for understanding the human ecological and climatological factors involved in the Late Pleistocene mass extinction event. This effort is paralleled with megafaunal mitogenomic assembly and phylogenetics solely from sediment. This thesis demonstrates that environmental DNA can significantly augment macro-scale buried records in palaeoecology.