LIFE AND TIMES OF THE BERING LAND-BRIDGE

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