It’s called the bomb-curve. Between 1952 and 1963, nuclear weapons test doubled the amount of radiocarbon in our atmosphere but dropped profoundly once nuclear tests were restricted to underground. The radioactive levels have since declined but they still absorbed by plants and enter the animal tissue upon consumption. The radiocarbon concentration found in animal tissue can accurately determine the year which the animal died all the way back to 1955 with a margin of error of four to 16 months. "The year an elephant died plays a big role in whether or not the trade of ivory is legal. Poached ivory makes it to market...
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