The study of human molecular genetics, made possible through the elucidation of the structure of DNA (Watson & Crick 1953), has in recent years contributed increasingly to the understanding of prehistory. Archaeogenetics, the study of the human past using the techniques of molecular genetics, now provides a framework for investigating the out-of-Africa expansion of our species, Homo sapiens, and the means of elucidating its later population history. It is also informative about the earlier hominin species Homo neanderthalensis.

DNA is the genetic material in all life forms that contains the information determining the form and function of the organism. All organisms, whether humans, fungi or bacteria, consist of cells. These cells are largely constructed of four macromolecular building blocks: proteins, lipids, carbohydrates and the nucleic acids (RNA and DNA). DNA works as the blueprint within each cell for the synthesis of the proteins. The structure of DNA is a double-stranded linear molecule, the so-called double helix. This contains linear sequences of the four chemical bases – adenine, cytosine, guanine and thymine – attached to the DNA backbone. DNA is passed on from one generation to another. In humans, specific cells, egg cells and sperm cells, are the vehicles of transmission.

In animals generally, nuclear DNA and mitochondrial DNA (mtDNA) are distinct entities within each cell, and their mode of inheritance differs. mtDNA is passed down only through the mother to her children. The greater part of the cell’s DNA is packaged into chromosomes that are located in the cell’s nucleus. Here it is necessary to distinguish between the Y chromosome and the other nuclear DNA from the point of view of inheritance. While the Y chromosome is passed down exclusively from father to son, the other nuclear DNA is passed down to the children from both parents.