Radiocarbon dating — the analytical method that established the extraordinary age of the Trail Creek tooth — works on the same basic principle that governs all radiocarbon dating, but its application to a single small tooth involved specific methodological considerations that are worth understanding.

Carbon-14, the radioactive isotope that radiocarbon dating measures, is produced in the upper atmosphere by cosmic ray bombardment of nitrogen atoms.

Once produced, carbon-14 is incorporated into atmospheric carbon dioxide, taken up by plants through photosynthesis, and distributed through the food chain into the tissues of all living organisms.

Living organisms maintain carbon-14 at approximately the same concentration as the atmosphere, because they are continuously exchanging carbon with their environment through food and respiration.

When an organism dies, this exchange stops.