Hi there!
In order to do fossil comparative anatomy and branching diagrams to explain the evolution of organism, scientists use radiocarbonation method.
Explanation:
Carbon-14 can combine with oxygen in the atmosphere to create carbon dioxide, which is then absorbed by plants and makes its way through the food chain. The amount of carbon-14 in living plants and animals matches the amount in the atmosphere, but when plants and animals die, they no longer absorb carbon-14.
Because radiocarbon has a known rate of decay, the scientists can now determine about how long it has been since the plant or animal was alive. The lower the amount of radiocarbon, the older the object.
(Sometimes, C-12 is also used)
