When it comes to determining the age of stuff scientists dig out of the ground, whether fossil or artifact, “there are good dates and bad dates and ugly dates,” says paleoanthropologist John Shea of Stony Brook University.
The good dates are confirmed using at least two different methods, ideally involving multiple independent labs for each method to cross-check results. Sometimes only one method is possible, reducing the confidence researchers have in the results.
And ugly dates?
“They’re based on ‘it’s that old because I say so,’ a popular approach by some of my older colleagues,” says Shea, laughing, “though I find I like it myself as I get more gray hair.”
Kidding aside, dating a find is crucial for understanding its significance and relation to other fossils or artifacts. Methods fall into one of two categories: relative or absolute.
