Fine Tuning Radiocarbon Dates

21 Mar 2020

An article in Science Advances (March 18th 2020) is interesting - see https://advances.sciencemag.org/content/6/12/eaaz1096 .. and https://phys.org/news/2020-03-fine-tuning-radiocarbon-dating-rewrite-anc... ... which promises much but delivers little. Radiocarbon dating was invented in the late 1940s and after improvements over the years it remains the standard method for dating artifacts in archaeology and other disciplines. If it's organic and old (they say up to 50,000 years ago which is a shift from the 40,000 years ago buffers as a result of jiggery pokery and Bayesian methodology) you can normally  date it in a C14 laboratory. A new study by Cornell University claims it requires another refinement. This will have relevance to current dates now accepted in the Mediterranean region (including the Levant). It affects prehistory as much as the date, for example, of Tutankhamun, a bit of populist gaff put in for effect. It will also have relevance to the dating of the Thera volcano, we are told.

Thera is dear to the heart of the lead author, Sturt Manning, but he has found that at a site in Jordan the C14 does not add up and an adjustment is required. The paper expands on this (as reported last year on the News) to include the general Mediterranean region (without addressing the bigger problem of a 150 year discrepancy in Assyria). That was dismissed as due to a diet of fish from the Euphrates and Tigris rivers but in this new study we are told that cosmic radiation is not constant. It fluctuates.

Tree rings were calibrated with C14 and introduced to archaeology in 1986 in order to make the radiocarbon method more reliable - or convincing. A single northern hemisphere calibration curve has been the basic unit of dating in Europe and the Mediterranean region for all that time. Now, Sturt Manning and colleagues say there is mounting evidence for small but substantial regional off sets. Is this an admission that even IntCal13 is not reliable - where tree rings and C14 are part of a brew of several different dating methods, even including the inexact speleotherms. That is not broached of course as it would make the study a dogs dinner. The discovery in Jordan, it seems, is going to have far reaching repercussions - or that is what we are led to expect as we read further down the pages. Whilst their criticism of a single calibration curve would seem to have merit a much bigger discrepancy is the differences in dates achieved by different laboratories. Radio carbon dating at the moment is something of a hotchpotch as once again it is being seen to be not as reliable as the laboratories would have us believe.  In this instance they aren't talking about much of a refinement - not enough to make revisionists sit up with excitement that is, but enough so as not to rock the boat too much.

Manning rules out a 1500BC date for the Thera eruption and opts for one between 1600 and 1550BC. This is actually quite an adjustment, as Manning has long opted for the 1628BC date for Thera (but see the link to an article on the Home Page of this web site (SIS), by Jonny McAneney and Mike Baillie, 'Absolute Tree Ring dates for the LBA eruption of Aniachak and Thera in light of a proposed revision of ice core chronologies' that was published in Antiquity volume 93 issue 367 in February 2019. Manning is opposed by recalcitrant historians, mainly Egyptologists who do not think such a high date is possible and prefer a date around 1500BC. The historians themselves ignore the 150 year C14 discrepancy at Nineveh as it would mean downdating their Egyptian chronology (as outlined by Nick Thom in a recent  talk at an SIS speaker meeting). How would Manning deal with an even lower date for the Thera eruption - one in the 1400s perhaps.