Abstract
The beginning of the Anthropocene, a proposed geological epoch denoting human-caused changes to Earth's systems, and what metrics signify its onset is currently under debate. Proposed initiation points range from the beginning of the Atomic Age to the Industrial Revolution to the adoption of agriculture in the early Holocene. Most of the debate centers on the effects of modern industrially oriented technological and economic development. The effects of preindustrial and preagricultural populations on Earth's systems are less commonly evaluated. Because the utility of the Anthropocene concept is to denote measurable impacts of human activity on Earth's systems, we argue that focusing on an exact date or single event ignores time-transgressive, spatially variable processes of anthropogenic ecosystem engineering. We argue instead for a flexible, anthropologically and ecologically informed conceptualization of the Anthropocene-one that recognizes spatial, temporal, and scalar variability in the effects of humans on Earth systems. We present evidence in support of an ecologically informed pre-Columbian Anthropocene in California using a meta-analysis of sedimentological, palynological, and archaeological data sets from California mountains. We argue that use of fire for resource management by pre-Columbian populations was sufficiently frequent and extensive enough to result in widescale anthropogenic modification of California's biota and that an Anthropocene therefore began in California by at least 650 years ago, centuries before the arrival of Europeans. Recognizing a pre-Columbian Anthropocene in California constructively conceptualizes a marker for human economic-ecological intensification processes that could be more meaningful for policy, resource management, and research than focusing on any single historical event.