DNA polymorphism refers to the occurrence of two or more alternative forms of a DNA sequence at a particular location, or locus, within a population, with the variants occurring at a frequency high enough to be considered normal genetic variation rather than a rare mutation. The term polymorphism is derived from the Greek words meaning “many forms.” DNA polymorphisms arise because the DNA sequence of individuals is not completely identical. Differences may occur in single nucleotides, in the number of repeated sequences, or in the presence or absence of particular restriction-enzyme recognition sites. Such variations are generally inherited according to Mendelian principles and can therefore be used as genetic markers in anthropological and biological research. DNA polymorphism is particularly important in biological anthropology because it provides a molecular basis for studying human biological diversity, population relationships, genetic variation, migration, ancestry and evolutionary history. Unlike many conventional anthropological traits, DNA markers are highly specific and can be examined at the molecular level. The study of DNA polymorphism has therefore strengthened population genetics and has provided researchers with powerful methods for comparing populations and individuals. One important class of DNA polymorphism is Restriction Fragment Length Polymorphism, commonly abbreviated as RFLP. RFLP refers to differences in the lengths of DNA fragments produced when genomic DNA is cut with specific restriction enzymes. Restriction enzymes are bacterial enzymes that recognize particular short nucleotide sequences, known as recognition sites, and cleave DNA at or near these sites. If a genetic variation changes a restriction-enzyme recognition site, the enzyme may either gain or lose its ability to cut the DNA. Consequently, DNA fragments of different lengths are produced in different individuals. The basic procedure for RFLP analysis involves several stages. First, DNA is isolated from a biological sample such as blood, saliva or other tissue. The purified DNA is then treated with a selected restriction enzyme. The enzyme cuts the DNA at its specific recognition sites, producing a collection of fragments of different lengths. These fragments are separated according to size by gel electrophoresis. Smaller fragments generally migrate more rapidly through the gel than larger fragments. The separated fragments can subsequently be transferred to a membrane and identified using complementary labelled DNA probes in a process historically associated with Southern blotting. The resulting pattern of bands represents an individual's RFLP profile. The differences between individuals arise because their DNA sequences may contain different restriction sites or insertions and deletions between restriction sites. For example, suppose a restriction enzyme normally cuts DNA at two locations, producing a fragment of a particular length. If a mutation alters one recognition site, the enzyme cannot cut at that position, and a larger fragment is produced. Thus, individuals carrying different alleles can show different fragment patterns. RFLPs are valuable because they are generally highly stable and can be inherited from