Amino racemization dating technique
The L- and D-amino acid ratios are determined by gas and liquid chromatography..
Likewise, it can occur in molten rock from a volcano.
The L-amino acids change to D-amino acids more or less steadily following death. As a result, remains of organisms that died long ago will have more D-amino acids than ones that died recently.
Aspartic acid (one of the 20 amino acids) is usually extracted from samples for this dating technique.
He was quoted as saying that he had discovered the basis of the method in 1968, and that it was so obvious and simple he was amazed it hadn't been discovered earlier.
As a matter of fact, the basis of this method had been discovered earlier and had been reported in a series of papers published by Hare, Mitterer and Abelson in 1967, 1968, and 1969.
It is based on the fact that amino acids (the building blocks of all proteins) exist in two mirror image forms, both of which otherwise have the same chemical structures.
The L-amino acid molecule form has an extension to the left, while the D-amino acid form has an extension to the right.
Paleoanthropologists frequently need chronometric dating systems that can date things that are many thousands or even millions of years older.
Each amino acid has two chemical groups, an amino group and a carboxyl group, which can form chemical bonds with other amino acids.
The amino group of one amino acid can combine with the carboxyl group of a second amino acid to form a "peptide" bond, and its carboxyl group can combine with the amino group of a third amino acid, and the chain can thus be extended indefinitely.
A compass needle would have pointed to the south pole during some periods and to the north pole during others.
Lava and volcanic ash deposits often contain the thermoremnant magnetic records of these reversals.
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Before clay is fired and while lava is still in a molten state, the very weak magnetic fields of individual particles are randomly oriented. Later, its thermoremnant magnetism is measured with a magnetometer.