Life and times of the Bering land bridge

Abstract

UNDERSTANDING the environment of the Bering land bridge and determining the timing of late Wisconsin inundation are important for several areas of study. These include: (1) the timing of the re-establishment of circulation between Pacific and Atlantic Oceans; (2) the timing of development of a northern biotic refugium and the closing of the bridge to species immigration; (3) Palaeoindian migration routes; and (4) palaeotopographic data for atmospheric general circulation models1. Late Wisconsin palaeobotanical and fossil insect data from the central and northern sectors of the Bering land bridge indicate widespread mesic shrub tundra environments even during the last glacial maximum. Contrary to previous hypotheses, we found no evidence of steppe tundra on the land bridge. New accelerator mass spectrometer 14C dates show much of the land bridge was above sea level and thus available for human and animal migration until 11,000 yr BP. Insect evidence suggests that summer temperatures at that time were substantially warmer than now.