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Genetic analyses are an important contribution to wildlife reintroductions, particularly in the modern context of extirpations and ecological destruction. To address the complex historical ecology of the sea otter ( Enhydra lutris ) and its failed 1970s reintroduction to coastal Oregon, we compared mitochondrial genomes of pre-extirpation Oregon sea otters to extant and historical populations across the range. We sequenced, to our knowledge, the first complete ancient mitogenomes from archaeological Oregon sea otter dentine and historical sea otter dental calculus. Archaeological Oregon sea otters ( n = 20) represent 10 haplotypes, which cluster with haplotypes from Alaska, Washington and British Columbia, and exhibit a clear division from California haplotypes. Our results suggest that extant northern populations are appropriate for future reintroduction efforts. This project demonstrates the feasibility of mitogenome capture and sequencing from non-human dental calculus and the diverse applications of ancient DNA analyses to pressing ecological and conservation topics and the management of at-risk/extirpated species.

During the last 10 years, we have learned a great deal about the potential for a coastal peopling of the Americas and the importance of marine resources in early economies. Despite research at a growing number of terminal Pleistocene archaeological sites on the Pacific Coast of the Americas, however, important questions remain about the lifeways of early Paleocoastal peoples. Research at CA-SRI-26, a roughly 11,700 year old site on California's Santa Rosa Island, provides new data on Paleoindian technologies, subsistence strategies, and seasonality in an insular maritime setting. Buried beneath approximately two meters of alluvium, much of the site has been lost to erosion, but its remnants have produced chipped stone artifacts (crescents and Channel Island Amol and Channel Island Barbed points) diagnostic of early island Paleocoastal components. The bones of waterfowl and seabirds, fish, and marine mammals, along with small amounts of shellfish document a diverse subsistence strategy. These data support a relatively brief occupation during the wetter "winter" season (late fall to early spring), in an upland location several km from the open coast. When placed in the context of other Paleocoastal sites on the Channel Islands, CA-SRI-26 demonstrates diverse maritime subsistence strategies and a mix of seasonal and more sustained year-round island occupations. Our results add to knowledge about a distinctive island Paleocoastal culture that appears to be related to Western Stemmed Tradition sites widely scattered across western North America., Competing Interests: The authors have declared that no competing interests exist.

Understanding the causes and consequences of previous climate changes is essential for testing present-day climate models and projections. Archaeological sites are paleoenvironmental archives containing unique ecological baselines with data on paleoclimate transformations at a human timescale. Anthropogenic and nonanthropogenic forces have destroyed many sites, and others are under immediate threat. In the face of this loss, previously excavated collections from these sites-referred to as legacy collections-offer a source of climate and other paleoenvironmental information that may no longer exist elsewhere. Here, we 1) review obstacles to systematically using data from legacy archaeological collections, such as inconsistent or unreported field methods, inadequate records, unsatisfactory curation, and insufficient public knowledge of relevant collections; 2) suggest best practices for integrating archaeological data into climate and environmental research; and 3) summarize several studies to demonstrate the benefits and challenges of using legacy collections as archives of local and regional environmental proxies. Data from archaeological legacy collections contribute regional ecological baselines as well as serve to correct shifting baselines. They also enable regional climate reconstructions at various timescales and corroborate or refine radiocarbon dates. Such uses of legacy collections raise ethical concerns regarding ownership of and responsibility for cultural resources and highlight the importance of Indigenous involvement in planning and executing fieldwork and stewardship of cultural heritage. Finally, we discuss methodologies, practices, and policies pertaining to archaeological legacy collections and support calls for discipline-wide shifts in collections management to ensure their long-term utility in multidisciplinary research and public engagement., Competing Interests: The authors declare no competing interest.

We live in an age characterized by increasing environmental, social, economic, and political uncertainty. Human societies face significant challenges, ranging from climate change to food security, biodiversity declines and extinction, and political instability. In response, scientists, policy makers, and the general public are seeking new interdisciplinary or transdisciplinary approaches to evaluate and identify meaningful solutions to these global challenges. Underrecognized among these challenges is the disappearing record of past environmental change, which can be key to surviving the future. Historical sciences such as archaeology access the past to provide long-term perspectives on past human ecodynamics: the interaction between human social and cultural systems and climate and environment. Such studies shed light on how we arrived at the present day and help us search for sustainable trajectories toward the future. Here, we highlight contributions by archaeology-the study of the human past-to interdisciplinary research programs designed to evaluate current social and environmental challenges and contribute to solutions for the future. The past is a multimillennial experiment in human ecodynamics, and, together with our transdisciplinary colleagues, archaeology is well positioned to uncover the lessons of that experiment., Competing Interests: The authors declare no competing interest.

The submersion of Late Pleistocene shorelines and poor organic preservation at many early archaeological sites obscure the earliest effects of humans on coastal resources in the Americas. We used collagen fingerprinting to identify bone fragments from middens at four California Channel Island sites that are among the oldest coastal sites in the Americas (~12,500-8,500 cal BP). We document Paleocoastal human predation of at least three marine mammal families/species, including northern elephant seals (Mirounga angustirostris), eared seals (Otariidae), and sea otters (Enhydra lutris). Otariids and elephant seals are abundant today along the Pacific Coast of North America, but elephant seals are rare in late Holocene (<1500 cal BP) archaeological sites. Our data support the hypotheses that: (1) marine mammals helped fuel the peopling of the Americas; (2) humans affected marine mammal biogeography millennia before the devastation caused by the historic fur and oil trade; and (3) the current abundance and distribution of recovering pinniped populations on the California Channel Islands may mirror a pre-human baseline.

Three archaeological sites on California's Channel Islands show that Paleoindians relied heavily on marine resources. The Paleocoastal sites, dated between ~12,200 and 11,200 years ago, contain numerous stemmed projectile points and crescents associated with a variety of marine and aquatic faunal remains. At site CA-SRI-512 on Santa Rosa Island, Paleocoastal peoples used such tools to capture geese, cormorants, and other birds, along with marine mammals and finfish. At Cardwell Bluffs on San Miguel Island, Paleocoastal peoples collected local chert cobbles, worked them into bifaces and projectile points, and discarded thousands of marine shells. With bifacial technologies similar to those seen in Western Pluvial Lakes Tradition assemblages of western North America, the sites provide evidence for seafaring and island colonization by Paleoindians with a diversified maritime economy.

Interdisciplinary study of coastal archaeological sites provides a wealth of information on the ecology and evolution of ancient marine animal populations, the structure of past marine ecosystems, and the history of human impacts on coastal fisheries. In this paper, we review recent methodological developments in the archaeology and historical ecology of coastal regions around the world. Using two case studies, we examine (a) a deep history of anthropogenic effects on the marine ecosystems of California's Channel Islands through the past 12,000 years and (b) geographic variation in the effects of human fishing on Pacific Island peoples who spread through Oceania during the late Holocene. These case studies--the first focused on hunter-gatherers, the second on maritime horticulturalists-provide evidence for shifting baselines and timelines, documenting a much deeper anthropogenic influence on many coastal ecosystems and fisheries than considered by most ecologists, conservation biologists, and fisheries managers.

Archaeological data from coastal shell middens provide a window into the structure of ancient marine ecosystems and the nature of human impacts on fisheries that often span millennia. For decades Channel Island archaeologists have studied Middle Holocene shell middens visually dominated by large and often whole shells of the red abalone (Haliotis rufescens). Here we use modern ecological data, historical accounts, commercial red abalone catch records, and zooarchaeological data to examine long-term spatial and temporal variation in the productivity of red abalone fisheries on the Northern Channel Islands, California (USA). Historical patterns of abundance, in which red abalone densities increase from east to west through the islands, extend deep into the Holocene. The correlation of historical and archaeological data argue for long-term spatial continuity in productive red abalone fisheries and a resilience of abalone populations despite dramatic ecological changes and intensive human predation spanning more than 8000 years. Archaeological, historical, and ecological data suggest that California kelp forests and red abalone populations are structured by a complex combination of top-down and bottom-up controls.