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The answer is :Radiocarbon dating
In radiocarbon dating, we use a radioactive isotope of carbon in organic material as our main factor of measurement.
Before this method started to become popular, the method that is used to determine the age of artifact was by measuring how deep it's burried, which is far more unreliable since there would be many factors that can caused the depth of the burial beside the age.
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my answer is the hard ones first because they get my brain moving.
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