EVOLUTIONARY HISTORY OF THE COII TRNA(LYS) INTERGENIC 9-BASE-PAIR DELETION IN HUMAN MITOCHONDRIAL DNAS FROM THE PACIFIC/

Length changes in human mitochondrial DNA (mtDNA) are potentially usef ul markers for inferring the evolutionary history of populations. One such length change is a nine base pair (9-bp) deletion that is located in the intergenic region between the COII gene and the Lysine tRNA ge ne (COII\tRNA(Ly5) intergenic region). This deletion has been used as a genetic marker to trace descent from peoples of East Asian origin. A geographic dine of the deletion frequency across modern Pacific Islan der populations suggests that the deletion may be useful for tracing p rehistoric Polynesian origins and affinities. Mitochondrial DNA sequen ce variation within two variable segments of the control region (CR) p ermits a number of inferences regarding the evolutionary history of th e 9-bp deletion that cannot be determined from frequency data alone. W e obtained CR sequences from 74 mtDNAs with the 9-bp deletion from Ind onesia, coastal Papua New Guinea (PNG), and American Samoa. Phylogenet ic and pairwise distribution analysis of these CR sequences pooled wit h previously published CR sequences reveals that the deletion arose in dependently in Africa and Asia and suggests possible multiple origins of the deletion in Asia. A clinal increase of the frequency of the 9-b p deletion across the three Pacific populations is associated with a d ecrease in CR sequence diversity, consistent with founder events. Furt hermore, analysis of pairwise difference distributions indicates an ex pansion time of proto-Polynesians that began 5,500 yr ago from Southea st Asia. These results are consistent with the express train model of Polynesian origins.