Researcher uses carbon dating ancient items
The proportion of carbon-14 to carbon-12 in the atmosphere therefore remains relatively stable at about 1.5 parts per billion.
One of the implied assumptions in radiocarbon dating is that levels of atmospheric carbon-14 have remained constant over time.
It cannot be applied to inorganic material such as stone tools or ceramic pottery.
The technique is based on measuring the ratio of two isotopes of carbon.
This turns out not to be exactly true, and so there is an inherent error between a raw "radiocarbon date" and the true calendar date.
To correct for this, scientists have compared radiocarbon dates from objects who's age is known by other means, such as artifacts from Egyptian tombs, and growth rings from ancient trees.
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Some of the carbon-14 might find its way into living creatures.
Climate science required the invention and mastery of many difficult techniques.
These had pitfalls, which could lead to controversy.
(Since humans have only existed in the Americas for approximately 12,000 years, this is not a serious limitation to southwest archaeology.) Radiocarbon dating is also susceptible to contamination.
If the ground in which an object is buried contains particles of coal or other ancient sources of carbon, radiocarbon testing may indicate that the object is far older than it really is.