HOW OLD IS IT? THE STORY OF DATING IN ARCHAEOLOGY MUSEUM OF NEW MEXICO PRESS POPULAR SERIES PAMPHLET NO. 2 HOW OLD IS IT? DATING IN ARCHAEOLOGY _by James Schoenwetter_ There is a whole field of science devoted to the invention and development of dating methods—or “clocks” as we may think of them. It is called _geochronology_, the science of dating events. There are relatively few geochronologists, scientists trained in the use of all kinds of dating methods and in the theories upon which these methods are based. Geochronologists tell us that there are two major types of clocks: those that tick at an absolute rate of speed which can be measured, and those which tick only once in a while. A clock of the first type yields what is called an _absolute_ date, revealing the number of hours, days, years, centuries or millennia since an event occurred. A clock of the second type yields what is called a _relative_ date, placing an event as before or after another event, but does not tell us exactly how far they are apart in time nor how long ago they occurred. Depending upon how accurate his date must be to solve the problem he has set for himself, the archaeologist will select absolute or relative dating methods. Often, of course, the type of clock he wishes to use is not available, and he must use the next best type. Probably he will try to use a number of clocks of different kinds on the problem since each clock will act as a check on the others.