As with the Basques, few Native Americans are group B, so they must have migrated to the Americas late enough to pick up the Rh positive gene, but too early to pick up the gene for B. (9) This migration probably took place across the land bridge that at one time connected Siberia to Alaska. As the last Ice Age ebbed and the lands warmed and glaciers receded, the rising water levels eliminated the land bridge between Asia and American, bottling up the Native Americans and a high-O enclave and preventing for another 10,000 years any communication between the continents. Forensic studies support this theory: in Chile no B or AB have been noted either in pre-Columbian or Colonial mummies