As a rule, carbon dates are younger than calendar dates: a bone carbon-dated to 10,000 years is around 11,000 years old, and 20,000 carbon years roughly equates to 24,000 calendar years. The problem, says Bronk Ramsey, is that tree rings provide a direct record that only goes as far back as about 14,000 years.

Potassium-argon dating Potassium-40 is a radioactive isotope of potassium that decays into argon-40. The half-life of potassium-40 is 1.3 billion years, far longer than that of carbon-14, allowing much older samples to be dated. K–Ar dating was used to calibrate the geomagnetic polarity time scale.

Over time, carbon-14 decays in predictable ways. And with the help of radiocarbon dating, researchers can use that decay as a kind of clock that allows them to peer into the past and determine absolute dates for everything from wood to food, pollen, poop, and even dead animals and humans.

Because carbon-14 decays at this constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon. The carbon-14 method was developed by the American physicist Willard F. Libby about 1946.

There are two main methods determining a fossils age, relative dating and absolute dating. Relative dating is used to determine a fossils approximate age by comparing it to similar rocks and fossils of known ages.

Carbon dating also cannot be used on artifacts over about 50,000 years old. These artifacts have gone through many carbon-14 half-lives and the amount of carbon-14 remaining in them is miniscule and very difficult to detect.

5,730 years

The slow, but variable turnover of cartilage makes it an unsuitable tissue for age determination. Although dental enamel is the hardest substance in the body, teeth are not routinely used in traditional radiocarbon dating due to fear of carbonate mineral exchange during centuries of burial.