Carbon dating is used to work out the age of organic material — in effect, any living thing. By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.

Why is carbon dating useful for dating living things?

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.

Why does carbon dating only work on things that were once alive?

The reason carbon dating works is that the fresh carbon-14 gets mixed in with the rest of the carbon in the atmosphere and, since its chemically identical to regular carbon, gets worked into whatever is presently absorbing atmospheric carbon.