Biostratigraphy: One of the first and most basic scientific dating methods is also one of the easiest to understand.
Layers of rock build one atop another — find a fossil or artifact in one layer, and you can reasonably assume it’s older than anything above it.
Though still heavily used, relative dating is now augmented by several modern dating techniques.
Radiocarbon dating involves determining the age of an ancient fossil or specimen by measuring its carbon-14 content.
Measuring carbon-14 in bones or a piece of wood provides an accurate date, but only within a limited range.
Says Shea: “Beyond 40,000 years old, the sample is so small, and the contamination risk so great, that the margin of error is thousands of years.
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.
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.