31. Incongruous Genes in America
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31 Incongruous Genes in America Examine well your blood. —William Shakespeare, A Midsummer Night’s Dream, 1.1, 1595 As suggested in the previous chapter, the study of human genetics, in­ clud­ ing biochemical and, especially, molecular genetics, is technical and fast developing and seems to offer criti­ cal evidence relevant to transoceanic investigations. According to the Ameri­ can anthropologist Kenneth Tankersley, “genome variation is rapidly becoming a powerful tool that is leading toward a quantum leap in our knowledge of human migrations and origins. . . . It is becoming increasingly evident that genetics in the twenty-­ first century will have as a profound effect on Ameri­ can archaeology as radiocarbon dating did during the twentieth century.”1 What gives molecular genetic studies the advantage over traditional physical-­anthropological investigations is that, as Stephen Jay Gould wrote, “the items of a DNA program are sufficiently numerous and independent to ensure that degrees of simple matching accurately measure homology.”2 The bio­logi­cal scientist Austin L. Hughes concluded, “Molecular-­biology data offer the promise of at last unlocking the prehistories of our own and other species.”3 The further back in time one goes, the more problematic is the interpretation of genetic comparisons, since phenomena such as demographic bottlenecks , founder effects, genetic drift, and natural selection all work toward increasing genetic differences among populations over time. Another point is that to the extent that cladistic trees (cladograms) assume permanent separation among diverging populations, such diagrams—of proximity of relationship constructed on the basis of genetic distances among those populations— are of limited usefulness for his­ tori­ cal reconstructions in instances in which there may have been genetic inputs from one or more outside source into selected geographic areas.4 In these situations, distinctive genetic markers, polymorphisms (variants) with no apparent evolutionary function and of restricted geographic distribution, may be particularly revealing of contacts, just as in the cultural realm minor Incongruous Genes in America / 341 but distinctive shared nonadaptive traits may signal contact and introduction. It is the presence of such markers, not populations’ overall gene-­ frequency averages , that count in this context. As the physician and Oxford genetic anthropologist Stephen Oppenheimer has reminded us, “The number of people who took a major cultural advance across a sea by trade routes or otherwise may appear quite small when measured as a proportion of the indigenous people that received it. The modern traces of those seminal transfers when measured as genetic or linguistic markers may thus be quite faint.”5 Whether or not Oppenheimer is punning here, sailors are notorious for being generous with their genes. Blood Will Tell Scientists study a number of genetically controlled phenotypic phenomena in humans that display polymorphisms. Among these are the chemical compositions of vari­ ous bodily secretions (for example, enzymes, earwax), chemical-­ tasting ability, and dermatoglyphics (fingerprints). As far as I know, none of these has yielded, or seems likely to yield, information particularly suggestive in the area of transoceanic interactions. Blood, however, is another matter. Although the subject is dauntingly technical even in the simplified form presented here, it constitutes a highly significant body of evidence regarding contacts. The ABO System Today, we are all familiar with the fact that human blood exists in four genetically controlled types with respect to what is called the ABO system. ABO blood group substances are protein and sugar compounds on the surfaces of red blood cells. During the mid-­ twentieth century, the differences in frequencies of the A, B, AB, and O types began to be considered useful genetic indicators of human affiliations and migrations, especially following the 1956 publication of the British geneticist A. E. Mourant’s The Distribution of Blood Groups in Animals and Humans. O appears to have been the origi­ nal human blood type. Other things being equal, O is also selected for over A, B, and AB because of occasional A/B fetal loss owing to blood-­ type incompatibility with O-­ type mothers. Presumed-­ later type A is commonest in the Near East and Europe, and later-­ still B in Asia and Africa. It was once thought that, except for difficult-­ to-­ account-­ for high levels of the A1 subtype among the Blackfoot in the Montana-­ Alberta border country and lesser levels among neighboring peoples, Ameri­ can Indians were almost exclusively of type O and that this was proof that there had not been any significant contacts from the East­ ern Hemisphere following initial Late Pleistocene settlement of the Americas (with the exception...


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