Researcher uses carbon dating ancient items
Back in the 1940s, the American chemist Willard Libby used this fact to determine the ages of organisms long dead.Most carbon atoms have six protons and six neutrons in their nuclei and are called carbon 12. But a tiny percentage of carbon is made of carbon 14, or radiocarbon, which has six protons and eight neutrons and is not stable: half of any sample of it decays into other atoms after 5,700 years.Over the past six decades, the amount of radiocarbon in people or their remains depends heavily on when they were born or, more precisely, when their tissues were formed.Forensic anthropologists at The University of Arizona took advantage of this fact in a recent study funded by NIJ.Archaeologists have long used carbon-14 dating (also known as radiocarbon dating) to estimate the age of certain objects.Traditional radiocarbon dating is applied to organic remains between 500 and 50,000 years old and exploits the fact that trace amounts of radioactive carbon are found in the natural environment.Although it sometimes requires taking minute samples of an object, even that damage may be unacceptable for some artifacts.
Reporting at the 239th National Meeting of the American Chemical Society (ACS), they said it could allow scientific analysis of hundreds of artifacts that until now were off limits because museums and private collectors did not want the objects damaged.
In contrast, from 1955 to 1963, atmospheric radiocarbon levels almost doubled.
Since then they have been dropping back toward natural levels.
The researchers now think that Chaco Canyon was much more than a leaderless conglomeration of people, but a hierarchically organized society with leadership inherited through the maternal line.
Typically, the only things found in prehistoric archaeological ruins to indicate elevated status are grave goods—the artifacts found with burials.
Throughout the Southwest it is unusual to find formal burials within structures, because most people were buried with limited grave goods outside housing compounds, but in excavations sponsored by the American Museum of Natural History and carried out in the 1890s at Chaco Canyon, archaeologists found room 33 in Pueblo Bonito—a burial crypt within a 650-room pueblo dating between 8—that contained 14 burials.