Radiocarbon dating assumes that the carbon 14carbon 12 ratio
While the small variations in isotope decay that have been reported may not invalidate all isotopic dating, they raise questions about the assumption of completely uniform decay rates.
A second assumption is that the sample being dated has not experienced any loss or contamination of C over its history.
Carbon-14 dates usually appear to be reasonably accurate whenever they can be checked against historical records.
For example, when the Dead Sea Scrolls were dated, three methods could be used: 1) Dates written in the documents themselves (like the date at the start of a letter) 2) Paleography, which uses the style of script used to write documents to date them, and 3) Carbon-14.
It is known that such variations have occurred, but it is thought they can be corrected for by comparing a sample’s C level with the standard curve constructed using samples of known age.