Archaeology, Historical Ecology, and Marginality

The California Islands provide a case study that suggests that historical depictions of many islands as marginal environments for hunter-gatherers have been exaggerated by the ecological effects of the introduction of exotic plants and animals, historically or prehistorically. The perception of island marginality is traditionally based on variables ranging from island size to remoteness, isolation, and limited resources. Located near a continent, the California Islands are neither remote nor isolated, and they now appear to have been richer in plant foods, marine resources, minerals, fuel, and freshwater, than previously believed. We discuss these issues and explore the implications for other islands around the world where similar transformations have affected views about their marginality for human settlement and sustainability.

Why Translocate?

Worldwide, prehistoric hunter-gatherers and horticulturalists translocated a variety of animals and plants to islands. Translocations enhanced island ecosystems, introducing animals and plants used for food or raw materials. We review recent zooarchaeology, genetics, and stable isotope data to evaluate the evidence for ancient translocations to the islands of Baja and Alta California. Native peoples likely translocated foxes, mice, ground squirrels, domesticated dogs, iguanids, and possibly skunks to some California Islands. Although some animal translocations were for subsistence or broader environmental enhancement, others were either unintentional (mice) or more closely associated with ritual and other cultural practices. The dearth of translocations tied directly to subsistence suggests that marginal island food sources were not a primary factor driving translocation.

Responding to Stress or Coping with Abundance?

Due to their isolation, insularity, and lower biodiversity, the islands of Alta and Baja California have often been perceived as marginal habitat for humans compared to the adjacent mainland. Recent archaeological work, however, has revealed a deep history of sustained human settlement on many of the islands from the Terminal Pleistocene to the present, where large Native American populations had complex economies, sophisticated maritime technologies, and elaborate material cultures. With modern restoration efforts, the native vegetation, fisheries, and hydrology of the islands is recovering, raising questions about the marginality of the islands prior to European contact. This chapter draws from archaeological and ecological data to argue that the California Islands were optimal habitat for humans, with ample resources, both marine and terrestrial.

Differences in Human Population Density between the California Islands and the Coastal Mainland

If the California Islands were marginal environments for the indigenous people who occupied them, human population densities on the islands should be significantly lower than the adjacent mainland coast. Reconstructing population densities at particular times in the past is fraught with methodological difficulties, but data from site sizes and densities, radiocarbon date distributions, and mission records give no indication that island population densities were significantly lower than along the coastal mainland. Population density measures provide little evidence of environmental marginality on the Northern Channel Islands. Human population densities on islands further south may have been lower than the northern islands, but do not appear to have been significantly different than the adjacent mainland coast.

Marginality, Conveyance of Goods, and Trade on California’s Islands

Since the Terminal Pleistocene, the waters of the California Bight have been centers of maritime exchange, where islanders traded with mainland peoples. Explanations for the development of these exchange systems have argued that the uneven distribution of material resources between island and mainland environments led to the intensive exchange of goods. New evaluations of island resources suggest, however, that key plant foods and other potential trade goods were not as scarce on the islands as once thought. These developments necessitate a reevaluation of the role of maritime exchange in the development of social and political complexity in the California Bight. This chapter argues that social interactions and ritual obligations were important drivers of California Island exchange, with a focus on value-added and luxury goods.

Mineral Resources on the Islands of Alta and Baja California

Until recently, with a few exceptions, California Islands were believed to be relatively impoverished in high-quality materials for making stone tools. This chapter summarizes the distributions of known mineral resources on the islands, including numerous sources identified during recent geoarchaeology surveys. For islands occupied since the Terminal Pleistocene, the availability of such resources may have changed significantly through time due to sea level rise and coastal erosion. There is spatial variability in the distribution of mineral resources, but we show that such resources were relatively abundant on many of California's islands. This has implications for understanding the antiquity of initial colonization of the islands, the development of exchange networks, and the marginality of island mineral resources.

Paleocoastal Landscapes, Marginality, and Early Human Settlement of the California Islands

If the California Islands were marginal for human settlement, why were several of them occupied more or less continuously since Terminal Pleistocene or Early Holocene times? The earliest human history of California's Islands is clouded by sea level rise, coastal erosion, dune building, and differential research intensity. Nonetheless, Paleocoastal sites are abundant on the Northern Channel Islands and Cedros Island, suggesting that they were optimal habitat for early hunter-gatherers, with ample food, freshwater, mineral, and other resources to sustain permanent settlement. Worldwide on islands where late Pleistocene or early Holocene human colonization occurred, climate shifts and massive landscape changes caused by postglacial sea level rise require detailed reconstructions of paleogeography and paleoecology to assess the potential productivity or marginality of islands or archipelagos.

The Potential Use of Seaweeds and Marine Plants by Native Peoples of Alta and Baja California

Archaeologically, the use of marine kelps and seaweeds is poorly understood, yet California's islands are surrounded by extensive and highly productive kelp forests with nearshore habitats containing more than 100 edible species. Historical accounts from around the Pacific Rim demonstrate considerable use of seaweeds and seagrasses by native people, but there has been little discussion of seaweeds as a potential food source on California's islands. This chapter summarizes the biology, diversity, ecology, and productivity of marine macroalgae and marine angiosperms in the California Bight, supporting the likely consumption of seaweeds in the past. The potential use of plentiful and nutritious seaweeds by California Island peoples has major implications for the perceived marginality of the islands.

Where Carbohydrates Were Key

The terrestrial ecosystems of California's islands have long been described as depauperate, with island peoples relying more heavily on marine resources and trading for plant resources with mainland neighbors. Island plant communities were decimated by more than a century of overgrazing, however, with heavy soil erosion and the introduction of non-native weeds. Since the removal of livestock, island plant communities are recovering dramatically, showing an unparalleled richness in plant taxa. Macrobotanical remains from island archaeological sites provide valuable data about plant use for the past 10,000 years, showing that island geophytes and grassland/forb fields were much more abundant and productive than previously thought. Island plants provided ample food, medicine, fuel, and raw materials for island peoples. This research has implications for understanding the archaeology and historical ecology of other islands or archipelagos where humans have heavily altered island ecosystems.

Historical Degradation and Ecological Recovery

Spanish arrival to Alta and Baja California in AD 1542 marked the beginning of widespread ecological changes for California Island ecosystems. Over several centuries, Native peoples were removed to mainland towns and missions, intensive commercial fisheries and ranching operations developed, and numerous exotic plants and animals were introduced. The ecological fallout was swift and extensive, with extinctions and extirpations, devegetation, severe soil erosion, damaged hydrology, collapsed fisheries, and other ecological impacts. Archaeologists have long recognized some of the effects of these historical impacts, but only after decades of restoration biology on the islands have we come to appreciate how dramatically ecological baselines have shifted since Spanish arrival. As a result, many of California's islands now appear to have been optimal rather than marginal for human occupation.