the last glacial maximum. triticeae cultivation may apply negative selection on dq8. while there were numerous members of triticeae species similar to mid-eastern wild triticeae in the americas, and a great number of domesticated plants in the new world, no single species of triticeae appears to have been domesticated in the new world, and no clear examples in closely related tribes of grasses. among new world grass species in post columbian times, one species of elymus has been domesticated for human consumption and another as a pastoral cultivar. this could be interpreted in 2 ways. first, that levels of dq8, negatively, inhibited the domestication of triticeae strains. second, that the absence of such cultivars more suitable than already developed cultivars allowed dq8 to rise or remain high, while dq2.5 levels in nw under much longer term selection have fallen, or a little of both. most of american cultivars were domesticated south of the rio grande (exceptions are caddo rice and texas varigated squash, etc.). wheat, particularly barley and rye, are preferential cultivars in cooler climate, whereas zea is more adaptive in tropical climates and some cultivars are relatively drought-tolerant, zea however lacks certain amino acids that must be supplemented by other foods to prevent malnutrition. the proximity of neolithization to the equator in the new world may have much to do with the unapparent negative selection of dq8 relative to the neolithization of western eurasia. rendering of hla-dq8 with insulin peptide in the binding pocket looking down over the binding groove dq8 and disease in europe, dq8 is associated with type 1 diabetes and coeliac disease (also known as celiac disease). the highest risk factor for type 1 diabetes is the hla dq8/dq2.5 phenotype. in parts of eastern scandinavia both dq2.5 and dq8 are high increases frequencies of late onset type i and ambiguous type i/ii diabetes. dq8 is also found in many indigenous peoples of asia, it was detected early on in the bedoin population of arabia where dq2.5 is frequently absent, and in these instances dq8 is solely associated hla in coeliac disease. in the united states, however there appears to be shift in autoimmune disease risk for immigrants from mexico. increased immunoreactivity of hispanics in houston appear to be associated with dr4-dq8. the haplotype may incur the highest risk for rheumatoid arthritis. in japan dq3 (dq7, dq8, dq9) is associated with myasthenia gravis in the early onset female population, though it does not appear dq8 has the greater role, there are similarities between myasthenia gravis in japan and that detected in the houston hispanic population, with dq8 associated with younger females relative to the associations of all other hla dq types. coeliac disease is on the rise in japan, and it is clear that dietary shifts are the reason, but, also there is no dq2.5 in japan while dq8 levels are moderate. the dr4 linkage many disease associated with dq8 have dual linkage with dr4, and certain dr4 (*0405) have independent and dependent risk association with dq8, for example with type 1 diabetes.