The archaeological literature warns against trusting the context of artifacts found within a vertisol due to the constant mixing of sediments caused by the shrink/swell properties of clays. These churning processes were thought to be the defining characteristic of vertisols until only the past few decades. It is now apparent that vertisols vary drastically based on a wide spectrum of variables and are fully capable of forming without churning processes. The Buttermilk Creek Site, Block A represents a prime example of a minimally developed vertisol. In addition, the site itself is a heavily occupied lithic quarry that has been almost continuously inhabited since Clovis and possibly Pre-Clovis times. This thesis takes a detailed look at the sediments and distribution of lithic artifacts from Block A of the Buttermilk Creek site to address the two following research objectives: 1) to determine if the archaeological context within the floodplain sediments at Block A has been disturbed by post-depositional processes, and 2) to identify discrete occupation surfaces within the vertic floodplain sediments at the site. These objectives are addressed using a variety of methods, including: 1) plotting the stratigraphic position of diagnostic artifacts, 2) determining the size distribution of debitage and artifact quantities throughout the floodplain deposits, 3) examining the distribution of cultural versus non-cultural lithic material, 4) recording the presence or absence of heat alteration in the deposits, 5) creating maps showing the degree of fissuring across the site, 6) analyzing differences in patination on artifacts, and 7) analyzing the presence of calcium carbonate on artifacts from all levels. Results from these analyses show that, despite the classification of sediments at Block A as a vertisol, vertical displacement of artifacts is largely absent. Chronologically ordered diagnostic points, consistently size sorted artifacts, and a lack of constant mixing of calcium carbonate throughout the profile suggest that artifacts found as deep as 20 cm below the Clovis-aged horizon represent intact cultural horizons. These oldest components found in Block A may represent some of the earliest known evidence of people in the New World.

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.