You have met two ways of putting finds in order: seriation and stratigraphy. Both say "earlier" or "later" but never "how long ago". Archaeologists keep these two kinds of date strictly apart.
Key idea
A relative date places something in order: older or younger than something else, or in the same phase. An absolute date places it in years on a calendar, with a margin of error: "c. 2500 BC", "AD 394", "1550 ± 30 BC".
Why it works
The two answer different questions and have different weaknesses. A relative date can be certain without any calendar: a layer sealed under a floor must be older than the floor. An absolute date gives a number but always with an uncertainty, and that uncertainty matters. Mixing them up leads to false precision, such as treating Petrie's sequence date SD 40 as a year.
| Statement | Kind | How it was reached |
|---|---|---|
| "The pit is younger than layer 5." | relative | stratigraphy: the pit cuts layer 5 |
| "Grave 12 is earlier than grave 31." | relative | seriation of pot types |
| "The jar was made in the reign of Thutmose III." | absolute, through the king list | a seal with his name, and the dates of his reign |
| "The seeds were harvested c. 2600 BC (± 50 years)." | absolute | radiocarbon, calibrated |
| "The house was built in the Middle Kingdom." | a period: absolute in the end, because periods are dated | pottery style, tied to dated sites |
Worked example: Which kind?
Classify: (a) "Layer 3 formed after layer 4." (b) "The coffin dates to c. 1000 BC." (c) "The amulet is in the same style as amulets from the late 18th Dynasty."
- (a) An order without a year: relative.
- (b) A year on the calendar with "c.": absolute.
- (c) A style match places it in a phase. The 18th Dynasty has a dated span, so it is absolute in the end, but only as good as the dates of that style.
Answer: (a) relative; (b) absolute; (c) a dating by style, tied to an absolute span.
Worked example: Combining both
A layer lies directly over a floor that contains a jar dated by radiocarbon to c. 1800 BC. What can you say about the layer?
- The floor is under the layer, so the layer is younger (relative).
- The jar on the floor dates the floor to about 1800 BC (absolute).
- So the layer formed after about 1800 BC: a relative order hung on an absolute date.
Answer: The layer is later than c. 1800 BC.
Common mistake
Mixing the two. "Earlier than the pottery in layer 3" is relative; "c. 2500 BC" is absolute. Ask: does this statement contain a year? If not, it is relative.
Egyptian history is mostly dated by the king lists and regnal years (see Dating by Regnal Years), then checked against astronomy and radiocarbon. The next topics take the scientific methods one by one.