Carbon 14 dating seal
The method was developed by Willard Libby in the late 1940s and soon became a standard tool for archaeologists.
Libby received the Nobel Prize in Chemistry for his work in 1960.
The new method is based on the fact that over the past 60 years, environmental levels of radiocarbon have been significantly perturbed by mid-20th-century episodes of above-ground nuclear weapons testing.
Before the nuclear age, the amount of radiocarbon in the environment varied little in the span of a century.
The researchers found that if they assumed tooth enamel radiocarbon content to be determined by the atmospheric level at the time the tooth was formed, then they could deduce the year of birth.
Since then they have been dropping back toward natural levels.
Unlike tooth enamel, soft tissues are constantly being made and remade during life.
Thus, their radiocarbon levels mirror those in the changing environment.
To determine year of birth, the researchers focused on tooth enamel.
Adult teeth are formed at known intervals during childhood.