If you wanted to date a fossil that you think is representat

If you wanted to date a fossil that you think is representative of the earliest life on earth, which isotope would you use: uranium-238, carbon-14, or potassium-40? Explain your answer.

Solution

If I want to date a fossil that you think is representative of the earliest life on earth, I would use Uranium-238. This is because only uranium - 238 dating will allow me to date the oldest fossils as it has a half life of 4.47 billion years as it decays to lead - 206. The half life of potassium-40 is 1.26 billion years and carbon-14 can only be used to find age of fossils from 100 to 50,000 years old