European y-chromosomal lineages in Polynesians: A contrast to the population structure revealed by mtDNA

We have used Y-chromosomal polymorphisms to trace paternal lineages in Poly nesians by use of samples previously typed for mtDNA variants. A genealogic al approach utilizing hierarchical analysis of eight rare-event biallelic p olymorphisms, seven microsatellite loci, and internal structural analysis o f the hypervariable minisatellite, MSY1, has been used to define three majo r paternal-lineage clusters in Polynesians. Two of these clusters, both def ined by novel MSY1 modular structures and representing 55% of the Polynesia ns studied, are also found in coastal Papua New Guinea. Reduced Polynesian diversity, relative to that in Melanesians, is illustrated by the presence of several examples of identical MSY1 codes and microsatellite haplotypes w ithin these lineage clusters in Polynesians. The complete lack of Y chromos omes having the M4 base substitution in Polynesians, despite their prevalen ce (64%) in Melanesians, may also be a result of the multiple bottleneck ev ents during the colonization of this region of the world. The origin of the M4 mutation has been dated by use of two independent methods based on micr osatellite-haplotype and minisatellite-code diversity. Because of the wide confidence limits on the mutation rates of these loci, the M4 mutation cann ot be conclusively dated relative to the colonization of Polynesia, 3,000 y ears ago. The other major lineage cluster found in Polynesians, defined by a base substitution at the 92R7 locus, represents 27% of the Polynesians st udied and, most probably, originates in Europe. This is the first Y-chromos omal evidence of major European admixture with indigenous Polynesian popula tions and contrasts sharply with the picture given by mtDNA evidence.