In last week’s London Jewish News, a local rabbi held forth for half a page on the unreliability of carbon dating and the literal truth of Genesis. Carbon dating, he said, was very unreliable. One example he cited was of a 1991 sample taken from some South African cave paintings, which dated the paint at 1,200 years old. Later, an art teacher from Capetown called Joan Ahrens saw the paintings in a museum and recognised them as her pupils’ work – they had been stolen from her garden.
This anecdote, with no external references apart from the name of the laboratory that had done the tests – the Oxford Radio Carbon Accelerator Unit- can be found on many Creationist websites:
The above are two of the more reputable sites – I won’t link to fundamentalist Baptist weirdos, for obvious reasons.
I was irritated at the lack of any independent source for this story, which is apparently what counts as an argument for the Young Earthers. So I phoned the ORAU.
The extremely helpful Dr Tom Higham checked through all 100-odd South African tests for 1991 (just after the lab had been opened), and found the sample in question. The painted rocks were found on Pietermaritzburg golf course in Natal, a considerable distance from Capetown.
There is a valid and interesting explanation for the results, which has been utterly ignored by the Creationist brigade. The paint contained carbon from a petrochemical source which *was* 1,200 years old, and this affected the results. There is no record of Joan Ahrens in the ORAU’s files, but nontheless Dr Higham confirmed that the paintings had later been identified as recent, and not the work of ninth-century Bushmen.
It’s clear that the lab and the museum which commissioned the tests should have looked more carefully at the paintings before putting them on display as authentic, but this is a criticism of their methods, not the dating technique. Raw data in any context is rarely useful.
I guess Creationists don’t know very much about carbon dating and radioactive decay. Dr Higham observed that a few examples have been picked out from the many thousands of tests run each year, and have then wilfully misunderstood them.
Incidentally, the Creationists have this both ways. Not only is carbon dating unreliable, but even if it is accurate, the results are dismissed with a comment that things were different 6,000 years ago (radioactive decay, refraction of light, dinosaurs, stupidity…).
I don’t think my little bit of research will change anything, but it was a simple and satisfying way to spend ten minutes.
Ooh, stop press. Having been upbraided for my appalling attempt at spelling the name of an obscure South African town, I Googled the correct spelling. An Italian forum comes up, detailing exactly what happened, only this time Ms Ahrens painted the rocks herself.