Dating of fossils by scientists

DNA analysis has the potential to add information on the nature of relationships between animals. Researchers are able to get a rough time-frame for fossils by relating them to the rock layers (stratigraphic sequences) in which they are found.

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Palaeomagnetism is based on the fact that the Earth’s magnetic field “wanders” and has reversed at known periods in the distant past.

The alignment of fine iron particles within sediments, relative to the magnetic field prevailing when the sediments were laid down, can be determined and used as a measure of age relative to known periods of reversed polarity.

After a fossil has been prepared and cleaned, it is studied in the laboratory.

There are many ways of examining fossils in detail.

Uranium Series Dating is also based on the decay of radioactive isotopes, in this case by measuring the proportions of uranium to lead or uranium to helium in an ancient sample.

Electron Spin Resonance (ESR) dating is based on natural radioactivity.The search for fossils begins with geological surveys.Some areas are more likely to yield fossils than others, and researchers normally concentrate their efforts on regions that have good, fossil-bearing rock such as the dolomitic limestone of the Cradle of Humankind and the ancient lake beds of East Africa.But a good measure of luck is also needed sometimes, as was the case in many of the Cradle of Humankind sites, which were first explored by miners.Hundreds of palaeontological sites in South Africa have been exposed by miners.Specimens are numbered and catalogued with reference to their position vertically and horizontally in the site.