Defending 'BP' dating
In her recent letter "Say no to new 'BP' system of dating" (ANU Reporter, June 3), Helen Uren appears to see the use of the "Before Present" label as new and ridiculous. Neither of these views is informed, and the author is presumably unaware of the history and justification of this term. Disciplines such as archaeology and geology have employed the BP nomenclature for decades, and the adoption of this term by Professor Barber simply reveals the archaeological nature of the data with which she deals. In reality referencing antiquity as years before the present is no less arbitrary than measuring in terms of years before an arbitrary date some 2,000 years ago. The claim made by Helen Uren, that the BP system is "ridiculous because dates will constantly need to be re-referenced" reveals a literal rather than informed and technical understanding of this system of chronological accounting. In radiometric dating methods it is not necessary to "re-reference" a date each year because the "Present" in BP is not literally today but rather a fixed point in time (typically the year 1950AD) internationally accepted by dating laboratories. The choice of 1950 AD as 0 BP is based largely on technical considerations (eg a point after which atmospheric nuclear testing altered the atmospheric composition). Hence the use of BP is neither ridiculous nor banal, but a well-established scientific scale of measurement justified by technical requirements of dating methods. Peter Hiscock Archaeology and Anthropology Australian National University