Bowheads killed in Inupiat subsistence hunts occasionally carried old weapon fragments under the skin. Several were nineteenth-century stone or ivory harpoon points, and one recovered in 2007 was part of an explosive lance patented in the 1880s. Because such gear went out of use, the whales carrying it had to have been struck more than a century earlier and survived.
An independent method agreed. Aspartic acid in the eye lens nucleus slowly converts from one molecular form to its mirror image at a roughly constant rate, and the lens is laid down before birth and never replaced. Applied to landed bowheads, the technique produced ages over a hundred for several animals and a central estimate above two hundred for one male.
The method carries real error bars, widening at great age, and rests on an assumed racemisation rate. It is the concordance of two unrelated lines of evidence, not either alone, that makes the bowhead the longest-lived mammal known.