Introduction

The study of the patterns of genetic diversity in modern human populations can help reconstruct human evolutionary history, including ancient migrations, population expansions, and bottlenecks. However, the interpretation of early events based on modern genetic patterns may easily be obscured by more recent developments, for instance, multiple migrations, invasions, or demographic collapse resulting from infectious diseases or genocide. Additional information in the form of linguistic analyses, historical reports or the archaeological record can be used to build some kind of approximate picture of our past. Moreover, the development of powerful techniques for DNA analysis, notably the polymerase chain reaction, enables us to gain direct genetic information about past peoples in the form of DNA amplified from bones or mummified soft tissues.

In recent years, mitochondrial DNA (mtDNA) has achieved a prominent place in the study of human evolutionary history because it is simple, easy to study and evolves quickly. The human mtDNA genome is a closed circular molecule of approximately 16 569 base pairs in length (Anderson et al., 1981) located in the cellular cytoplasm. It contains only 37 genes, no introns, and little other non-coding DNA besides the 1 kb (kilobase) control region. The mtDNA genome is inherited in a maternal fashion, without recombination, and evolution occurs by the accumulation of mutations through time.