Before more precise absolute dating tools were possible, researchers used a variety of comparative approaches called relative dating.
These methods — some of which are still used today — provide only an approximate spot within a previously established sequence: Think of it as ordering rather than dating.
Researchers can first apply an absolute dating method to the layer.
They then use that absolute date to establish a relative age for fossils and artifacts in relation to that layer. Anything below the Taupo tephra is earlier than 232; anything above it is later.
One of these phrases is "stashing," which refers to when you're in a supposedly serious relationship with someone, but they don't introduce you to any of their friends.
Whenever possible, researchers use one or more absolute dating methods, which provide an age for the actual fossil or artifact.
Sometimes only one method is possible, reducing the confidence researchers have in the results. “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.
Certain unstable isotopes of trace radioactive elements in both organic and inorganic materials decay into stable isotopes. By measuring the proportion of different isotopes present, researchers can figure out how old the material is.
Here are some of the most common radiometric methods: Radiocarbon dating: Sometimes called carbon-14 dating, this method works on organic material.