In human genetics, the Atlantic modal haplotype (AMH) or haplotype 15 is a Y chromosome haplotype of Y-STR microsatellite variations, associated with the Haplogroup R1b. It was discovered prior to many of the SNPs now used to identify subclades of R1b and references to it can be found in some of the older literature. It corresponds most closely with subclade R1b1a2a1a(1) [L11].
It reaches the highest frequencies in the Iberian Peninsula, in Great Britain and Ireland. In the Iberian Peninsula it reaches 70% in Portugal as a whole, more than 90% in NW Portugal and nearly 90% in Galicia (NW Spain), while the highest value is to be found among Spain and the Basques.
One mutation in either direction, would be AMH 1.15+. The AMH 1.15 set of haplotypes is also referred to as the Atlantic modal cluster or AMC.