Radiocarbon dating methodology
First used, and likely invented by archaeologist Sir William Flinders-Petrie in 1899, seriation (or sequence dating) is based on the idea that artifacts change over time.
Like tail fins on a Cadillac, artifact styles and characteristics change over time, coming into fashion, then fading in popularity. The standard graphical result of seriation is a series of "battleship curves," which are horizontal bars representing percentages plotted on a vertical axis.
His research culminated in proving that tree ring width varies with annual rainfall.
Not only that, it varies regionally, such that all trees within a specific species and region will show the same relative growth during wet years and dry years.
For example, JJA Worsaae used this law to prove the Three Age System.
Seriation, on the other hand, was a stroke of genius.
Plotting several curves can allow the archaeologist to develop a relative chronology for an entire site or group of sites.
For detailed information about how seriation works, see Seriation: A Step by Step Description.
The basis for stratigraphy seems quite intuitive today, but its applications were no less than earth-shattering to archaeological theory.Absolute dating, the ability to attach a specific chronological date to an object or collection of objects, was a breakthrough for archaeologists.Until the 20th century, with its multiple developments, only relative dates could be determined with any confidence.For example, since each Roman emperor had his own face stamped on coins during his realm, and dates for emperor's realms are known from historical records, the date a coin was minted may be discerned by identifying the emperor depicted.Many of the first efforts of archaeology grew out of historical documents--for example, Schliemann looked for Homer's Troy, and Layard went after the Biblical Ninevah--and within the context of a particular site, an object clearly associated with the site and stamped with a date or other identifying clue was perfectly useful. Outside of the context of a single site or society, a coin's date is useless.