In the past, relative dating methods often were the only ones available to paleoanthropologists.
As a result, it was difficult to chronologically compare fossils from different parts of the world.
This technique is useful to about 9,000 years ago for samples from the western United States using overlapping tree-ring series from living and dead wood.
The Earth's orbital motions (inclination of the earth's axis on its orbit with respect to the sun, gyroscopic precession of the earth's axis every 26,000 years; free precession every 440 days, precession of earth orbit and orbital variations such as perihelion precession every 19,000 and 23,000 years) leave traces visible in the geological record.
The emergence of man through the process of biological and cultural evolution is a story of long span of time.
In other words, Chronology is the arrangement of events, or the materials which represent them, in the order of their occurrence in time.
This is a fossil skull of Homo Erectus, found in Africa. Dating geological specimens involves an interdisciplinary approach using more than one dating method and cross-validating the results.
Absolute dating methods include radiometric, luminescence and incremental dating.
Trees usually add growth rings on a yearly basis, with the spacing of rings being wider in high growth years and narrower in low growth years.
Patterns in tree-ring growth can be used to establish the age of old wood samples, and also give some hints to local climatic conditions.