Abbreviation for "years before present," a unit of time used in anthropology, geology, and paleontology. By international convention, the year 1950 CE (or AD) represents the present, so years "BP" are really years before 1950
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}