Besides radiometric dating, several other lines of evidence can be used to determine the age of fossils. These include:
- Stratigraphy: Stratigraphy involves the study of rock layers or strata in which fossils are found. By examining the position of fossils within different layers of sedimentary rock, scientists can determine their relative age. The principle of superposition states that in undisturbed rock layers, younger layers are deposited on top of older layers.
- Biostratigraphy: This method involves comparing the fossils found in different rock layers to establish their relative ages. Fossils of known ages or those with well-established age ranges can be used as markers or index fossils for dating the surrounding rocks.
- Paleomagnetism: The Earth's magnetic field has undergone reversals in the past, and rocks and fossils can retain a record of these magnetic reversals. By studying the alignment of magnetic minerals in fossils or rock layers, scientists can determine their approximate age.
- Dendrochronology: Dendrochronology, also known as tree-ring dating, uses the analysis of tree rings to determine the age of wooden artifacts and fossils found in proximity to trees.
- Index Fossils: Index fossils are commonly used to date rock layers. These fossils are species that existed for a relatively short period of time but were widespread geographically. By finding index fossils in a specific layer of rock, scientists can correlate the age of that layer with other locations where the same index fossils are found.