method is based upon the decay of radioactive potassium-40 to radioactive argon-40 in minerals and rocks; potassium-40 also decays to calcium-40.
Thus, the ratio of argon-40 and potassium-40 and radiogenic calcium-40 to potassium-40 in a mineral or rock is a measure of the age of the sample.
The age of the fossil must be determined so it can be compared to other fossil species from the same time period.
Understanding the ages of related fossil species helps scientists piece together the evolutionary history of a group of organisms.
But without knowing exactly when each neuron was created, scientists couldn’t say with any certainty that this was true.The bomb pulse has been declining since the 1963 above-ground test ban treaty, creating a sort of clock they could exploit.By determining how many radioactive carbon atoms a cell contained, Spalding and Frisén hoped they could calculate its birthdate. Spalding’s curiosity eventually leading her to a slaughterhouse on the outskirts of Stockholm.For example, based on the primate fossil record, scientists know that living primates evolved from fossil primates and that this evolutionary history took tens of millions of years.By comparing fossils of different primate species, scientists can examine how features changed and how primates evolved through time.