Tracking the evolutionary history of the Warrior gene across the South Pacific: Implications for genetic epidemiology of behavioral disorders
Historically, the New Zealand Maoris were extremely adventurous risk takers and fearsome warriors. A DNA repeat polymorphism in the neuronal Monoamine Oxidase (MAO) gene on the X chromosome is strongly associated with risk taking and aggressive behaviour. Hence, the gene has been dubbed the “Warrior” gene. The MAO gene is known to be highly polymorphic in human populations and there is new evidence that the full spectrum sequence variation across MAO exhibits unusual patterns of linkage disequilibrium (LD) indicative of positive selection.
Interestingly, our unpublished studies have revealed striking over-representation of the MAO repeat polymorphism in the Maori male population compared to Caucasian males. We have also characterised LD among SNPs spanning the entire gene in Maori and identified 2-tagging SNPs that signify the common haplotype. This MAO haplotype is associated with the Warrior allele in Maori males suggesting that variation in the MAO gene has been under the influence of positive selection during the risky Polynesian voyages and wars.
Cultural, linguistic and genetic evidence points to Formosa (Taiwan) as the staging post of Maori (Polynesian) voyages between 5000-10000 years ago. In light if this, we will also present full comparative genomic data of the MAO gene in Taiwan aboriginal tribes in an effort to elucidate the evolutionary history of the Warrior gene in the South Pacific. Understanding the evolution of the MAO gene will also be useful for studies of human behavioral disorders such as alcohol and tobacco dependence.