By comparing fossils of different primate species, scientists can examine how features changed and how primates evolved through time.
Third, magnetism in rocks can be used to estimate the age of a fossil site.
Using this technique, called radiometric dating, scientists are able to "see" back in time.
Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4.6 billion years.
There are three general approaches that allow scientists to date geological materials and answer the question: "How old is this fossil?
" First, the relative age of a fossil can be determined.