How Old Is It? The Story of Dating in Archeaology

THE STORY OF DATING IN ARCHAEOLOGY
MUSEUM OF NEW MEXICO PRESS POPULAR SERIES PAMPHLET NO. 2
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.
The absolute clock utilized most widely in archaeology is the historical record. Men have used calendars for a long time, and have often left records with written dates. On tombstones at a site in old Virginia, on the pedestals of statues and other monuments from classical Greece and Rome, on the walls of the tombs of Egyptian kings, dates are clearly inscribed which can be related to the sites dug into by the archaeologists. These dates must often be recalculated in terms of the Christian calendar which we use. Most calendars in use in the Mediterranean, the Near East and China during classical antiquity have been successfully correlated with the one we use today, and a date inscribed or noted on such sites can be considered in our own terms. Other calendars, such as those developed in the ancient cultures of the Maya on the Yucatan Peninsula, have yet to be accurately correlated with our own. Such calendars can be used on their own terms of course, and a site which has an inscription in the Mayan calendar is known to be so many years older or younger than another one with a different date in that calendar. We speak of such a situation as a floating chronology . That is, the sequence of events and the number of years which separate them are known, but the dates of those events in absolute time are unknown.