Averages by geographic region of PAH haplotype frequencies. Frequencies of haplotypes of four SNP sites were estimated for 30 populations and unweighted averages calculated for geographic regions whenever there were two or more populations in a region. "Europe" includes populations in Southwest Asia. The numbers of populations averaged is shown at the right. The eight most common haplotypes (of the 16 possible) are distinguished by the color/shading. Haplotypes are labelled for the four sites in their order along the chromosome (BglII, PvuII, MspI, XmnI) with a 1 for the site-absent allele and a 2 for the site-present allele.