Though still heavily used, relative dating is now augmented by several modern dating techniques.
Radiocarbon dating involves determining the age of an ancient fossil or specimen by measuring its carbon-14 content.
By contrast, methane created from petroleum showed no radiocarbon activity because of its age.
The results were summarized in a paper in Science in 1947, in which the authors commented that their results implied it would be possible to date materials containing carbon of organic origin.
The method was developed by Willard Libby in the late 1940s and soon became a standard tool for archaeologists.