The half-lives of several radioactive isotopes are known and are used often to figure out the age of newly found fossils.Different isotopes have different half-lives and sometimes more than one present isotope can be used to get an even more specific age of a fossil.
You would need to have access to scientific instruments at this point that could measure the amount of radioactivity in the sample, so off to the lab we go!
After you prepare your sample and put it into the machine, your readout says you have approximately 75% Nitrogen-14 and 25% Carbon-14.
Early geologists, in the 1700s and 1800s, noticed how fossils seemed to occur in sequences: certain assemblages of fossils were always found below other assemblages. Since 1859, paleontologists, or fossil experts, have searched the world for fossils.
In the past 150 years they have not found any fossils that Darwin would not have expected.
All these labors have not led to a single unexpected finding such as a human fossil from the time of the dinosaurs, or a Jurassic dinosaur in the same rocks as Silurian trilobites.