At an archaeological dig, a piece of wooden tool is unearthed and the archaeologist finds it to be 5,000 years old.A child mummy is found high in the Andes and the archaeologist says the child lived more than 2,000 years ago.Once an organism dies, it stops taking in carbon-14.The carbon-14 it contained at the time of death decays over a long period of time, and the radioactivity of the material decreases.
Forensic anthropologists at The University of Arizona took advantage of this fact in a recent study funded by NIJ.
The man's body was recovered and pieces of tissue were studied for their C content by accelerator mass spectroscopy.
The best estimate from this dating technique says the man lived between 33 BC. From the ratio, the time since the formation of the rock can be calculated.
Compared to conventional radiocarbon techniques such as Libby's solid carbon counting, the gas counting method popular in the mid-1950s, or liquid scintillation (LS) counting, AMS permitted the dating of much smaller sized samples with even greater precision.
Regardless of the particular 14C technique used, the value of this tool for archaeology has clearly been appreciated.
Desmond Clark (1979:7) observed that without radiocarbon dating "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation." And as Colin Renfrew (1973) aptly noted over 30 years ago, the "Radiocarbon Revolution" transformed how archaeologists could interpret the past and track cultural changes through a period in human history where we see among other things the massive migration of peoples settling virtually every major region of the world, the transition from hunting and gathering to more intensive forms of food production, and the rise of city-states.