This handout photograph taken in April 2005 and obtained on August 18, 2026 from Greenland Institute of Natural Resources shows narwhals with their tuskd in Uummannaq, West Greenland. Narwhals have nature's only straight tusk, a single tooth up to three metres long so strange they were sold as magical unicorn horns during the Middle Ages. On August 18, 2026, a large international team of researchers announced they had solved a long-running mystery about the tusks: how they get their uniquely spiralled yet arrow-straight form. (Photo by Mads-Peter Heide JORGENSEN / Greenland Institute of Natural Resources / AFP via Getty Images) / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / Greenland Institute of Natural Resources / Mads-Peter Heide Jorgensen " - HANDOUT - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS