Radiocarbon dating of charcoal from Lascaux Cave in France dates these graphic cave paintings to about 15,000 BCE. Lascaux Cave was designated a UNESCO World Heritage Site in 1979.
The isotope carbon-14 (C-14) is particularly useful for dating organic objects (i.e., once-living materials). While an object is alive, the ratio of C-14 to C-12 remains constant. Once an object dies, however, the unstable C-14 will start to decay. C-14 has a half-life of 5,730 years. By measuring the current ratio of C-14 to C-12 in an organism, it is possible to determine how much time has elapsed since this organism died. This method of determining the absolute age of an object is known as radiocarbon dating. This method is particularly useful for determining the ages of bones, wood, and charcoal.
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The ratio of C-14 to C-12 in living organisms is very small, only 1.3 × 10–12 to 1. After an organism dies, the C-14 will start to undergo radioactive decay. After about 10 half-lives, the amount of C-14 remaining is so small that it can’t be reliably detected with current technology. Since 10 half-lives for C-14 translates into approximately 60,000 years, this means that radiocarbon dating is only useful for materials up to 60,000 years in age.