Final answer:
The principle stating that fossils found lower in sedimentary layers are older is known as the law of superposition, which is part of relative dating methods in paleobiology.
Step-by-step explanation:
The Principle of Relative Dating
In paleobiology, the principle that fossils found lower down in sedimentary layers at a particular locality are older than those found closer to the surface is referred to as the law of superposition. This is a core concept in relative dating methods, which help determine which fossils are older or younger relative to one another, but do not provide precise ages in years. The assumption is that lower layers, being deposited earlier, contain older fossils, and this concept is fundamental in fields like stratigraphy and biostratigraphy to infer geological ages and study past climates or speciation rates.
Stratigraphic superposition and the study of rock layers (strata) are essential relative dating techniques. These methods allow paleobiologists to create a chronological sequence of events and to develop the fossil record, which provides evidence of when organisms lived and how life on Earth has changed over time.