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Gene frequencies for 13 marker systems are used to construct synthetic gene frequency maps of South America. The surfaces generated using the first three principal components exhibit clines which validate models of population displacement based on archeological data and a previous analysis of craniometrical variation.

Mummies' demographic information of 10 prehispanic cultures that developed in the Arica region of Chile about 7000 years ago is analyzed and related to the present population structure. A paleoepidemiological analysis supports a relationship between cultural development and demographic structure. In chronological sequence, 4 demographic patterns can be distinguished: 1) archaic, a mature population with the highest life expectancy and the lowest dependence from prehispanic populations; 2) later archaic, a population in demographic explosion with its larger fraction under 15 years of age, elevated fertility rates and the greatest prehispanic dependence; 3) andean, a transition population with moderate fertility rates and dependence index; and 4) modern, an aging population with the highest proportion over 45 years of age and the highest life expectancy. The present demographic analysis may help to understand the relationships among disease, individual and culture from the perspective of genetic epidemiology.

Chagas disease is present in northern and central Chile. Not more than 25% of infected individuals have had a pathologic condition presumably due to Trypanosoma cruzi. The majority of individuals with chronic infectious Chagas disease in Chile are asymptomatic in contrast to what has been observed in other South American countries. Historic and paleopathologic evidences suggest that this particular behavior could be explained by a genetic adaptation of Chilean aborigines to T cruzi. Associations between ethnic admixture, presence of Chagas disease, associated cardiac pathology and 4 blood groups (ABO, MNSs, Rh and Duffy) were investigated among inhabitants of San Pedro de Atacama in northern Chile. Cardiac pathology was determined by positive serologic reactions in individuals with abnormal electrocardiographic findings. Individuals with negative serologic results had a significantly greater aboriginal admixture (88%) compared to those with positive serology (66%). This findings supports the hypothesis of genetic adaptation explaining mildness of Chagas disease in Chile.

We studied the distribution of HLA, B and C antigens in 73 Chagasic subjects with and without heart disease. Both groups were matched for age, sex, birth place and history of family residence. Thirty two subjects without evidence of Chagasic infection, with and without heart disease and matched for the same variables were also studied. Compared to all other groups, a significant increase in the level of the B40 Cw3 antigen combination was found in Chagasic subjects without evidence of heart disease.

Using the polymerase chain reaction to amplify genomic DNA from hair roots, we have examined the mitochondrial aldehyde dehydrogenase (ALDH2) genotypes of 28 individuals from the South American Mapuche Indians. We have determined that individuals from this population previously reported to lack (ALDH2) activity do not show the presence of the inactive (ALDH2(2] allele frequently found in Orientals.

The independent contributions of climate, altitude, chronology, and geographic location of archeological sites to craniometrical variation are analyzed in a sample of 1,119 skulls from South America. Geographic location is responsible for the highest proportion of craniometrical variation, followed by climate and altitude. It is concluded that geographic isolation has partially prevented gene flow from counterbalancing craniometrical microdifferentiation produced by founder effect.

Mahalanobis D2 statistics (with size and shape components) were computed for nine craniometric variables among five prehistoric groups representing steps in the microevolutionary history of a coastal population in Northern Chile. Roughly 80% of craniometric variation was found to be explained by chronologic distance covering a period of roughly 6500 years. Kinship decreases in this population at a relatively constant rate of 8.6 X 10(-5) per year.

Multivariate distance statistics were computed from 14 nonmetrical cranial variables among five prehistoric samples representing steps in the microevolutionary history of a coastal population in northern Chile. Roughly 70% of nonmetrical cranial variation was found to be explained by chronologic distance covering a period of 6,500 years. This estimate is similar to a previous one derived from craniometric data. Implications of these findings are briefly discussed.

The joint effect of adiposity, high altitude, age and indigently on systolic and diastolic blood pressure is studied in an Indian population living at high altitude in Northern Chile. Adiposity (Quetelet's index), accounted for the highest percentage of explained variability, followed by high altitude and age. Indigently was shown to have an insignificant effect on blood pressure, indicating that Andean aboriginal populations did not differ genetically from lowland populations with respect to this variable.

Recovery of night vision at altitude has been examined in relationship to changes of 2,3,diphosphoglycerate (DPG). It appears that, if DPG influences night adaptation, its effect is small. Inter-individual variability is large, both in terms of DPG and performance on the MESOP, the device used to measure dark adaptation.

Electrophoretic variants at 22 genetic loci in the Aymara, mestizo, and Spanish populations of northern Chile are presented, and their possible role in adaptation to hypoxic environments are discussed. Some apparently unique variants were found.

Archeological, craniometrical, and genetic information is utilized to reconstruct possible migration routes used in the peopling of Andean South America. Special emphasis is given to the elaboration of craniometrical isoline maps and its application in testing models of population displacement based on archeological data. A genetic distance analysis among linguistic groupings complements the conclusions based on archeological and craniometrical information.

The association of anthropometrics, particularly hand measurements, with dermatoglyphic characters is quantified. Children with square hands exhibit higher main line indices, a-b ridge counts, and more open atd angles. Adults with broader hands have more arches. Taller individuals with larger hands present higher a-b ridge counts and leaner subjects with long narrow hands, closer atd angles. The correlation of physique and dermatoglyphics is small but if verified, suggests that at early fetal stages, factors responsible for the establishment of dermatoglyphic patterns interact with genetic determinants of adult shape that are already active.

Routine ophthalmoscopy and fundoscopy of 673 individuals revealed 42 whose irides failed to dilate to a clinically useful degree within 25 to 30 min after the administration of drops of 1% mydracil. These individuals occurred with different frequency among the Aymara, Mestizo, and non-Aymara groups which made up the sample of examinees. The phenomenon was most common among the Aymara, less common among the Mestizos, and least common among the non-Aymara. Distribution of affected individuals within the three groups suggests that the trait is inherited.

Dermatoglyphic data on 15 traits (digital arches, digital radial loops, digital ulnar loops, digital whorls, I loops, Ir loops, H loops, H loops, III loops, IV loops, mainline C absence, total ridge count, a-b ridge count, atd angle, and mainline index) are presented for 141 Chipaya Indians of Bolivia. Ethnic relationships of these Indians to nine South American Indian tribes (Alacaluf, Atacameño, Aymara, Cashinahua, Chácobo, Chama, Chané, Quechua, and Sirionó) are explored by means of a genetic distance analysis using 21 alleles. Genetic distances are complemented with linguistic and geographic distances between the Chipaya and the other tribes. Genetic distances were found not to be significantly correlated with linguistic and geographic distances. Combining the information available, it is concluded that the Chipaya are most likely ethnically related to the Arawak speakers of the tropical forest.

While about 40% of the South American Indian populations (Atacameños, Mapuche, Shuara) were found to be deficient in aldehyde dehydrogenase isozyme I (ALDH2 or E2), preliminary investigations showed very low incidence of isozyme deficiency among North American natives (Sioux, Navajo) and Mexican Indians (mestizo). Possible implications of such trait differences on cross-cultural behavioral response to alcohol drinking are discussed.

The results of ABO typing in Chilean mummies, a review of published South American paleoserological studies and a systematic discrepancy of admixture estimates based on ABO and Gm genes support the hypothesis that Andean pre-Columbian populations possessed the A (and perhaps the B) gene in small frequencies.

The quest for the origin and dispersion of Chagas' disease, the second most important vector-borne disease in Latin America, has epidemiological, immunological, and genetical implications. Conjectures based on accounts of chroniclers, reviews of the archaeological literature and the present distribution of triatomine bugs, the vectors of the disease, held that the origin of the adaptation of Triatoma infestans (a species of the subfamily Triatominae) to human dwellings occurred in prehistoric times. The autopsy of 35 mummies exhumed in the Chilean desert, dated between 470 B.C. and 600 A.D., revealed the presence of clinical manifestations of Chagas' disease and put earlier speculations on a factual basis.

Studies of lung function in high altitude populations have suggested the influence of hypoxic environment on the development of this characteristic independent of confounding variables such as ethnicity and habitual exercise. However, often the effect of altitude on vital capacity is greater in children than adults, suggesting that more than developmental adaptation is operative. Also selective migration could account for the similarity of migrants and permanent residents at a destination altitude. To explore these problems we studied the lung function (FVC, FEV1, PFR) of 377 individuals who had migrated between altitudes in northern Chile. Migrant measurements were adjusted to those of permanent residents of appropriate age, sex and height at the altitudes of origin and destination. The measurements were then related to ethnicity (Spanish-Aymara ancestry), occupation and permanence, the latter combining information on both age at migration to and length of stay at a destination altitude. Upward migration was associated with increased chest depth, FVC and FEV1, but not height or other chest measurements. Downward migration had no significant effect. The flow-dependent test PFR was so sensitive to observer variability and occupation that it was difficult to establish its relationship to permanence. Unlike the body measurements, lung function measurements (especially PFR) tended to deviate from permanent controls at the origin altitude in a direction suggestive of selective migration, nor was permanence itself independent of ethnicity and occupation. Because of these difficulties the question of developmental adaptation in lung function may not be answerable in cross-sectional studies like the present and previous efforts, but rather in longitudinal investigations in which the control is the individual him/herself.

The sex dimorphism for adult stature is compared in four Chilean populations which differ in their Amerindian ABO blood group composition. Statistical analysis revealed a significant association between sex dimorphism and Amerindian admixture in these populations. Assuming, on one hand, that sex chromosomes have an influence on adult stature and human growth and considering, on the other, that the four populations differ in their X and Y chromosome composition as a consequence of an asymmetrical inter-racial marriage practice, it is postulated that the observed association between sex dimorphism and Amerindian gene composition is a result of this peculiar mating structure.

The use of dermatoglyphic traits to describe interpopulational diversity among human populations at various levels of differentiation is compared with similar analysis of gene frequency data by means of nonparametric methods employing distance matrices and dendrograms, and by a partition of total variability into its between and within population components. Congruence of dermatoglyphics and gene markers appears to vary with level of population differentiation -- the association remains insignificant until racial level of differentiation is considered. Different pitfalls of the data used are mentioned. The interpretation of these findings is discussed by comparison with other non-human studies.

The present study reports the results of erythrocyte antigen typing for the following systems: ABO, MN, Rh, Kell, Duffy, and Diego in roughly 180 Atacameño Indians from the oasis of Toconao, northern Chile. A subsample was tested for variation at the histocompatibility loci A, B, and C. Results agree with previous findings based on smaller samples. Caucasian admixture of the Atacameño from Toconao was estimated to be 0.056 +/- 0.022.

Myths and facts concerning the heredity of human alcohol abuse are discussed in this article. Familial aggregation, adoption studies, twin concordances, marker gene associations and, finally, recent biochemical and genetic evidence are examined critically. It is concluded that with the exception of a possible protective action of the ALDH2 gene in Japanese there is a lack of clear cut evidence with respect to the direct participation of genetic factors in human alcoholism.

The distribution of HLA antigens in a sample of 124 Chagas serologically positive Chilean individuals was studied. The sample was subdivided according to the presence or absence of chagasic cardiomyopathy, in order to search for genetic differences associated with this pathological condition. The frequency of antigen B40 in the presence of antigen Cw3 was found to be significantly lower in subjects with cardiomyopathy. We tentatively suggest that the presence of these antigens among noncardiomyopathics is associated with a decreased susceptibility to develop chagasic cardiomyopathy in the Chilean population.

In 1972 a multidisciplinary study sought to assess the health status of the indigenous peoples of the Department of Arica in northern Chile, the Aymara, and to relate disease, morphological, physiological and biochemical variation, to the wide changes in altitude of the region. Presented here are the morphological changes which accompany age, altitude and ethnicity amoung 1047 children and adults, permanent residents of the coast, sierra and altiplano. At comparable ages, high-altitude residents were shorter, lighter and leaner but with more expansive and rounder chests than sea-level controls. None of these effects was systematically related to ethnicity (Spanish-Aymara surname), although when stature was held constant, children with greater Aymara ancestry had largest chest circumferences and longer bones. These results suggest that (1) altitude confers allometric growth changes (expensive growth of the chest and diminished growth of the structures less related to oxygen transport); and (2) size changes associated with altitude are acquired during development while shape changes may be under genetic control. Altitude appears to account for less of the variation in growth in this relatively homogeneous Chilean sample than has been reported for other Andean samples, suggesting other concomitants confounding the effects of hypoxia in Andean South America.