He has analyzed clamshells to gain perspective on the Vikings, who migrated from Europe's mainland to Iceland, Greenland, and northeastern stretches of north America hundreds of years before Columbus.

他分析了蛤壳以了解有关维京人的过去，维京人在哥伦布之前数百年就从欧洲大陆迁徙到冰岛，格陵兰和北美东北部绵延的大陆。