A 24,000-year sequence recorded in a marine core from the Santa Barbara Basin, off the coast of California, exhibits the highest peak in biomass burning precisely at the onset of the Younger Dryas. ... This anomalously high peak correlates with intense biomass burning documented from the nearby Channel Islands. ... The peak also coincides with the extinction of pygmy mammoths on the islands and with the beginning of an apparent 600-800-year gap in the archaeological record, suggesting a sudden collapse in island human populations.