In this way large domed tombs (known as tholos or beehive tombs) in Greece were thought to predate similar structures in the Scottish Island of Maeshowe.This supported the idea that the classical worlds of Greece and Rome were at the centre of all innovations.From these records a “calibration curve” can be built (see figure 2, below).
The calibrated date is also presented, either in BC or AD or with the unit cal BP (calibrated before present - before 1950).
The calibrated date is our “best estimate” of the sample’s actual age, but we need to be able to return to old dates and recalibrate them because new research is continually used to update the calibration curve.
Some of the first radiocarbon dates produced showed that the Scottish tombs were thousands of years older than those in Greece.
The barbarians of the north were capable of designing complex structures similar to those in the classical world.
In 2008 we could only calibrate radiocarbon dates until 26,000 years.
Now the curve extends (tentatively) to 50,000 years.
Luckily, we can measure these fluctuations in samples that are dated by other methods.
Tree rings can be counted and their radiocarbon content measured.
Radiocarbon dates are presented in two ways because of this complication.
The uncalibrated date is given with the unit BP (radiocarbon years before 1950).
In the 19th and early 20th century incredibly patient and careful archaeologists would link pottery and stone tools in different geographical areas by similarities in shape and patterning.