ABO Phenotype and Morphology
| Autor: | A. J. Kelso, Kenneth L. Beals, Courtland L. Smith |
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| Rok vydání: | 1992 |
| Předmět: | |
| Zdroj: | Current Anthropology. 33:221-224 |
| ISSN: | 1537-5382 0011-3204 |
| DOI: | 10.1086/204058 |
| Popis: | The existence of naturally occurring blood-group antigens without obvious benefit to the individual having them is one of the more perplexing and widely investigated problems in biology. The assumption of the nonadaptive (selectively neutral) character of ABO antigens has led to racial classifications in which blood-group frequencies are taken as selectively neutral and therefore markers of population affinity. While Boyd's (I95o) dictum that these substances are "completely unaffected by the environment" has yet to be disproven by direct evidence, a growing body of circumstantial data suggests that selective elements do influence ABO frequencies. These adaptive hypotheses include disease, diet, environmental interactions, heterozygote advantage, and heterozygote disadvantage. ABO maternal/fetal incompatibility is well documented. The theoretical problem this presents is that such incompatibility implies the action of natural selection against heterozygotes (the offspring) and thus against maintaining the polymorphism, but the occurrence of allelic varieties in nonhuman primates implies they have been present as a polymorphism for millions of years. As Brues (I954) has shown, the clustering of alleles suggests the probable existence of some balancing or counteracting effect. Numerous factors have been proposed as environmental agents with sufficient strength to overcome the effects of maternal/fetal incompatibility. In very brief summary, type A may be connected to smallpox and gastric-system carcinomas and 0 to gastric ulcers and perhaps influenza, plague, and malaria, though such reported pathological associations are not universally found. Moreover, a cultural factor is involved in zygosis. Even if maternal/fetal incompatibility occurs, different alleles will be reintroduced into populations if isolation breakdown is present. Blood-group zygosis is known to be associated with the level of social organization (low heterozygosity in bands, high heterozygosity in states [Beals and Kelso I975]). When ABO frequencies are compared with population morphology means, they often appear to be mechanisms that might explain variances with body size and shape. A glance at a map of the frequency of the IA allele compared with the surface-area data depicted by Beals, Smith, and Dodd (I984) clearly suggests an empirical connection; the IA allelic frequency has long been known to display a north-south cline, and so does body weight. A further suspicion of an ABO/morphology connection arises from the tabulation of ABO frequencies (Mourant, Kopec, and Domaniewska-Sobczak I976). For example, the heavily built Papago (67 kg male and female mean) have virtually no B and AB phenotypes, while the diminutive Efe (37 kg) have 37% the latter. Such distributional connections suggest a physiological relationship between the antigens and metabolism. Other evidence lends support to this idea. Kelso (i962) and Kelso and Armelagos (I963) reported on relations between diet and the distribution of ABO frequencies. Angel (I957, cited in Slatis and Finkel I963) found a higher than expected frequency of the AB phenotype among obese individuals. Many of the diseases associated with ABO types are gastrointestinal (see Otten I967, Mourant, Kopec, and Domaniewska-Sobczak I978). Kelso et al. (I972) reported that type-A college females were significantly heavier than females of other blood types. Reed (I967, I968), Kelso et al. (personal communication), and Kircher (I963) found significant weight differences among the various ABO phenotypes in infants. Arfors, Beckman, and Lundin (I963) reported that a variant of the enzyme serum alkaline phosphatase was associated with blood-types 0 and B and suppressed by A. Jensen et al. (I988) report that the individual profile of carbohydrates in human milk may be related to blood type. The presence of ABH antigens in the digestive tissue of secretors has long been recognized; recently it has become clear that they are major allogenic antigens of most epithelial cell types (Clausen and Hakamori I989). Recent indirect supporting evidence of an ABO role in digestion may be found in Jensen et al. (I988) and Yamamoto et al. (I990). Thus, the physiological and therefore the adaptive significance of the ABO polymorphism may lie at least in part in the role it plays in metabolism or, more basically, in tissue recognition. Moreover, the suggestion of such a role appears early in ontogeny and in at least one instance seems to operate in one gender only. Exploring these possibilities lies beyond the scope of this investigation. We have examined all reports known to us in which ABO frequencies among populations can be matched |
| Databáze: | OpenAIRE |
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