A scientist who found deep grooves chiselled into the teeth of dozens of 1,000-year-old Viking skeletons unearthed in Sweden believes the strange custom might have been learned from aboriginal tribes during ancient Norse voyages to North America -- a finding that would represent an unprecedented case of transatlantic, cross-cultural exchange during the age of Leif Ericsson. The marks are believed to be decorations meant to enhance a man's appearance, or badges of honour for a group of great warriors or successful tradesmen. They are the first historical examples of ceremonial dental modification ever found in Europe, and although similar customs...