dating english china Radiocarbon dating and evolution

There are several different methods for estimating the ages of fossils, including: Paleontologists rely on stratigraphy to date fossils.

Stratigraphy is the science of understanding the strata, or layers, that form the sedimentary record.

For example, if fossils of B date to X million years ago and the calculated “family tree” says A was an ancestor of B, then A must have evolved earlier.It is also possible to estimate how long ago two living branches of a family tree diverged by assuming that DNA mutations accumulate at a constant rate.The principle of radiocarbon dating is simple: the rates at which various radioactive elements decay are known, and the ratio of the radioactive element to its decay products shows how long the radioactive element has existed in the rock.This rate is represented by the half-life, which is the time it takes for half of a sample to decay.If a fossil is found between two layers of rock whose ages are known, the fossil’s age is thought to be between those two known ages.

Because rock sequences are not continuous, but may be broken up by faults or periods of erosion, it is difficult to match up rock beds that are not directly adjacent.Protons and neutrons make up the center (nucleus) of the atom, and electrons form shells around the nucleus.The number of protons in the nucleus of an atom determines the element.Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geological time scale.Beds that preserve fossils typically lack the radioactive elements needed for radiometric dating (” radiocarbon dating ” or simply “carbon dating”).Scientists use a technique called radiometric dating to estimate the ages of rocks, fossils, and the earth.