Of the African rock art that has been scientifically dated so far, the oldest images are in Namibia, from about 27,000 years ago. Yet most experts agree that some of Africa's rock art may date to more than 50,000 years ago, Coulson said.
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As I understand it, dating art imprinted on stones, are pretty much guesses or approximations based on carbon-dating of organic matter on and/or around the said stones and perhaps on the material used to draw on the said stones, since apparently, the stones themselves cannot be dated via carbon-dating.
See, for examples used in dating techniques used to date rock art:
...and here's a piece in a link directed from the above link, which may be worth noting:
The criteria of direct rock art dating are clear, precise and rigorous. Direct dating does not produce actual ages of rock art, it generates testable propositions about the relevance of specific physical or chemical data to the true age of rock art. The interpretation of the relation demands a considerable understanding of the dating technique used; of the circumstances of sample collection, processing and distorting factors; and of the limitations and quite specific qualifications applying to the stated results. None of the methods used in direct dating of rock art produces results that can be conveyed by some simple numerical expression, which unfortunately is how they are often quoted in the archaeological literature. Therefore it is fair to say that archaeologically published results of direct dating are often presented in a misleading form. Such results should always be understood within the context they were acquired and within which the archaeometrists expect them to be seen (Bednarik 1996, 2000a; Watchman 1999).
Consider, for instance, the ubiquitous radiocarbon analysis results, and the way they are misused (see Pitfalls in rock art dating).
There are very few kinds of circumstances in which a carbon-14 result can directly be related to the age of rock art, and so far (in 2001) no rock art has been dated by radiocarbon.
This is not what one would be led to believe if one sifted through recent archaeological commentaries. - Robert G. Bednarik
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