Absolute Dating

What is absolute dating?

Absolute dating consists of pegging down one or more elements in a relative sequence to fixed BC/AD dates. All historic chronologies depend on working back from the present (often in terms of known sequences of rulers). For the Mediterranean world, such a sequence exists back to Roman times. We know, for instance, that the Emperor Augustus ruled from 31 BC to AD 14. Further sequences are then added on to the Roman one: Greek relative dating (based on Olympic years), and the kings of Egypt such as Akhenaten back (with varying margins of error) to the First Dynasty in the early third millennium BC. This works because of the known (Roman) dates for the Roman conquest of Greece (146 BC) and Egypt (30 BC).

Head of Augustus from the Sudan. © The Trustees of The British Museum.

Material evidence can be tied to the absolute dates of Egyptian, Greek or Roman history. For example, the relative sequence of portrait types of the Emperor Augustus can be dated absolutely because one of the types can be dated to before 25 BC. A head of this type was looted from Egypt by a Meroitic raid in 25 BC and buried in the steps of a temple at Meroe in the Sudan (where it was subsequently discovered by archaeologists).

Radiocarbon dating

Trypiti Gorge from the sea. Wave notch visible. (1988) © Sphakia Survey

There is another, scientific means of dating ancient material: radiocarbon. This technique has been increasingly refined since its first use ca.50 years ago, and now offers secure dating ranges for objects containing carbon (e.g. wood, plant remains, clothing). This technique is very helpful for some periods of prehistory.

For historic periods the extent of the date range means that radiocarbon does not produce information that cannot be obtained from other dating techniques, but even there it can be helpful. For example, the Sphakia Survey has analysed radiocarbon dates for sea creatures raised from the sea by sea level changes, and this has produced a reliable date for a major uplift of western Crete in the Late Roman period.

More famously, the radiocarbon analysis of the Turin Shroud proved that it dates not to the time of Christ, but to the Middle Ages. But, even though this technique is 'scientific', we must remember that its results are based on the interpretation of scientific findings and are therefore (like all of science) subject to revision.