So rock samples that should read zero are occasionally placed into the instruments to test their accuracy.
What better samples to use than fossils, coals, and limestones, which are supposed to be millions of years old and should have no radiocarbon?
The age for all these fossils was found to be less than 50,000 years1.
But while the difficulties of single life may be intractable, the challenge of determining the age of prehistoric artifacts and fossils is greatly aided by measuring certain radioactive isotopes.
Other corrections must be made to account for the proportion of throughout the biosphere (reservoir effects).
Additional complications come from the burning of fossil fuels such as coal and oil, and from the above-ground nuclear tests done in the 1950s and 1960s.
Carbon-14 is also passed onto the animals that eat those plants.
After death the amount of carbon-14 in the organic specimen decreases very regularly as the molecules decay.