Multivariate classification of human populations. I. Allocation of Yanomama indians to villages.

A set of 12 anthropometric measures and six genetic traits, available for 520 Yanomama Indians from 19 villages in nine clusters, were used to allocate individuals to villages. On the basis of anthropometrics alone, 36% of the individuals were allocated to the right village and 60% to the right cluster. On the basis of genetic traits alone, 16% were allocated to the right village and 26% to the right cluster. A combination of all 18 characters yielded 41% allocation to the right village and 63% to the right cluster. Of the 924 possible combinations of six anthropometric measures, only one provided poorer resolution than did the six genetic traits. We explain the better resolution of the anthropometric traits by noting that the anthropometric traits are not totally heritable and that genetic traits are not continuously distributed. Randomization studies indicated that all of the observed correct-allocation fractions are far in excess of random expectation. We infer that the village phenotype distributions overlap only partially, and that they represent real and substantial population differentiation.     

Genetic structure of a tribal population, the Yanomama Indians. XIII. Dental microdifferentiation.

Data are presented on the frequency of the following eight dental traits in 635 Yanomama and 65 Makiritare Indians: upper central incisor rotation or winging, shoveling of maxillary incisors, maxillary molar hypocone reduction, Carabelli's trait, mandibular molar cusp number, mandibular molar cusp pattern rotation of second lower premolar, and pattern of second lower premolar cusps. Yanomama dentition is unusual in the high frequency of six cusps on the mandibular molars. There is marked dental microdifferentiation between villages; significant agreement was observed between a matrix of pairwise "dental distances" based on six morphological traits and corresponding matrices based on 11 genetic systems and on geographic location.     

The influence of cultural factors on the demography and pattern of gene flow from the Makiritare to the Yanomama Indians

A single village of Yanomama Indians was found to have frequencies of Di^a of 0.06 and of Ap^a of 0.08, in contrast to 40 other villages whereDi^a was absent and Ap^a quite rare. The source of these genes was identified as a village of Makiritare Indians, but the two allele frequencies were approximately the same or even higher in the Yanomama than in the Makiritare village. Demographic, social and cultural parameters affecting marriage and reproduction in the two tribes explain this. Genealogical relationships and informants' accounts collected in the field, when viewed against the traditional marriage practices, reproductive advantages of headmen, and differential treatment of captured women, indicate that the mating and reproduction parameters inherent in tribal social organization of this kind constitute an essential part of the explanation of the genetic findings. It is argued that mating systems of this sort are such that the probability of a new gene introduced by a captive surviving in the recipient population is a function of the sex of the initial carrier. The implications for tribalization and potentially radical changes in allele frequencies are briefly explored by considering aspects of settlement pattern and population fissioning known to characterize the tribes in question. Finally, it is shown that genetic sampling from a single location can and does result in unrepresentative allele frequencies when this single sample is taken to characterize the tribe as a whole.     

The Genetic Structure of a Tribal Population, the Yanomama Indians. VI. Analysis by F-Statistics (Including a Comparison with the Makiritare and Xavante

The infra-structure of three relatively undisturbed tribes of American Indians (Yanomama, Makiritare, Xavante) has been investigated by means of the F-statistics of Wright, using 8, 9 and 6 codominant systems respectively. The data for the first two mentioned tribes are much more extensive (37 and 7 villages) than for the third (3 villages), and much of the argument is based on the first two. An additive model partitioning F(IS) into an average effect (F(A)) and deviations due to deme size, systems effects, village effects, and random error has been employed. The Cannings-Edwards formulation suggests that the small size of the demes alone would result in an F(IS) of -0.008 for the Yanomama and -0.007 for the Makiritare. There is no evidence for significant village or systems effects. Despite considerable scatter, F(A) values are not significantly heterogeneous and tend to be negative (-0.012 to -0.023). On the basis of a computer simulation model, it appears that there is an excess of consanguineous marriage over random expectation, i.e. the negative F(A) values are probably not due to avoidance of close inbreeding in a subdivided population in which demes are small. Aspects of population structure which could contribute to negative F(A) values are identified. These include unequal gene frequencies in the sexes and occasional marked differential fertility. It is at this point unnecessary to introduce overdominance as a cause of the negative F(A) values, since a computer simulation program which does not incorporate selection satisfactorily reproduces the observed F(IS) values. If population breeding structure alone can result in negative F(IS) values, then this may constitute a mechanism for retarding random fixation.-Mean F(ST) values are 0.063 for the Yanomama and 0.036 for the Makiritare. While truly comparable data are lacking, it seems likely these will be found to be relatively high values for human populations. F(IT) values have been calculated by both direct and indirect approaches. The direct approach yields a value of 0.045 for the Yanomama and -0.009 for the Makiritare; the respective indirect values are 0.085 and 0.017. The primary identifiable reason for this difference between tribes is the greater genetic heterogeneity among Yanomama villages. The assumptions underlying the indirect approach to the calculation of F(IT) do not appear to be met in these populations.     

The Genetic Structure of a Tribal Population, the Yanomama Indians. Xiv. Clines and Their Interpretation

The Yanomama Indians are a South American tribe distributed over an irregular area approximately 200 x 300 miles. The gene frequencies observed at 12 loci in 47 villages within this area have been analyzed for the occurrence of clines. Apparently significant clines are observed for alleles of the Rh, MNSs, Kidd, Gm, Inv and serum albumin system. Available data concerning recent tribal expansion and admixture permit a tentative analysis of the causes of these clines. Although the action of selection cannot be rigorously excluded, it seems unlikely to be the major cause. Admixture with surrounding tribes plays a role which can be quantified because of the fortuitous circumstance of two genetic markers for admixture. It is suggested that an important factor in the origin of these clines is the manner in which the tribe has recently expanded through successive village fissionings and a predominantly centrifugal pattern of village migration.     

The genetic structure of a tribal population, the Yanomama Indians XI. Gene frequencies for 10 blood groups and the ABH-Le secretor traits in the Yanomama and their neighbors; the uniqueness of the tribe.

In this paper we present the results of blood group typings for a total of 33 villages distributed among five South American Indian tribes--Yanomama (21 villages), Makiritare (eight villages), Macushi (two villages), Piaroa (one village), and Wapishana (one village). These new results for the Yanomama and Makiritare tribes have been combined with those previously reported to allow a better appreciation of the distribution of allelic frequencies in the tribes. The relationship of the Yanomama to other South American Indian tribes is investigated using data on six polymorphic loci (Rh, MNS, Fy, Jk, Di, Hp). By use of four genetic measures (two of genetic relationship and two of genetic diversity), we demonstrate that the Yanomama are genetically unique among a sample of 20 South American tribes. In addition, the Yanomama show somewhat less genetic diversity for the six loci analyzed than the average South American tribe. Taken together, these results indicate a rather long period of isolation for the population antecedent to the Yanomama--perhaps since the time of entry of man into the South American continent. The pattern of genetic relationships and genetic diversity for the 20 tribes is consistent with the hypothesis that evolution in South America proceeded by a process of fission-fusion leading to isolation of subpopulations with subsequent genetic differentiation as a consequence of population isolation. The uniqueness of the Yanomama appears to stem entirely from such a process, there being no evidence of any selective differential for the loci analyzed.     

The genetic structure of a tribal population,the Yanomama Indians. XII. Biodemographic studies

The Yanomama Indians of Southern Vanezuela and Northern Brazil are one of the largest, relatively unacculturated tribes of the tropical rain forest. Over a period of eight years data have been collected from a considerable portion of their territory on estimated age, sex ratio, fertility rates (as determined by physical examination and urine tests), and infant death rates. Although it has been impossible to collect direct data on infanticide, this subject can be approached indirectly through distortions of the sex ratio and anecdotal information. Some historical data are also available as a basis for estimating tribal expansion in the past 100 years. With this material it has been possible to construct Life Tables for the Yanomama, and to explore the results of various perturbations of the input parameters. Data are also presented on patterns of mating and reproduction: number of spouses, mean and variance in number of surviving children, frequency of “extra-marital conceptions” based on the results of extensive blood group typings, and consanguinity rates as determined by observation and computer simulation. Although we do not present the Yanomama as typical, these data are seen as providing a basis for more realistic population models than have existed in the past. In addition, the data provide a basis for relatively precise estimates of such demographic measures as Fisher's Reproductive Value, Crow's Index of Total Selection, and Weiss' Index of Growth Regulation.     

The Genetic Structure of a Tribal Population, the Yanomama Indians. Xv. Patterns Inferred by Autocorrelation Analysis

Fifteen allele frequencies have previously been determined for 50 villages of the Yanomama, an Amerindian tribe from southern Venezuela and northern Brazil. These frequencies were subjected to spatial autocorrelation analysis to investigate their population structure. There are significant spatial patterns for most allele frequencies. Clinical patterns, investigated by one-dimensional and directional spatial correlograms, were relatively few in number and were moderate in strength. Overall, however, there is a marked decline in genetic similarity with geographic distance. The results are compatible with a hierarchic population structure superimposed on the geography, and generated by a stochastic fission-fusion model of village propagation, followed by localized gene flow. Strong temporal autocorrelations of allele frequencies based on linguistic-historical distances representing time since divergence were also found. There appears to be a stronger relation between geography and linguistic-historical hierarchic subdivisions than between either feature and genetic distances. These findings confirm by different approaches the results of earlier analyses concerning the important roles of both stochastic and social factors in determining village allele frequencies and the occurrence within this tribe of some allele frequency clines most likely due to the operation of chance historical processes.     

Multivariate Analysis of Gametic Disequilibrium in the Yanomama

The gametic disequilibria between all possible pairs of loci were examined for a set of eight codominant loci in each of fifty Yanomama villages, using a multivariate correlation analysis which reduces the results to a single measure of departure from multiple-locus-gametic equilibrium. Thirty-two of the fifty villages departed significantly from multiple-locus gametic equilibrium. The largest contributions to the departure from multiple-locus equilibrium were due to the disequilibria between MN and Ss and between Rh(Cc) and Rh(Ee), indicating the effects of tight linkage. After removing the effects of these obvious sources of disequilibrium, sixteen of the fifty villages still remained significantly out of equilibrium. The disequilibrium between any particular pair of loci was highly erratic from village to village, and (with the exception of the MN-Ss and Cc-Ee disequilibria) averaged out very close to zero overall, suggesting a lack of systematic forces (epistatic selection). The departure from equilibrium in any one village is in excess of that expected from random sampling alone, and is attributed primarily to the fission-fusion mode of village formation operative in the Yanomama and the fact that a single village consists of a few extended lineages. Village allele frequencies are highly correlated across loci, and most of the non-independence is accounted for by large correlations in the average allelic frequencies of different loci for related villages. It is suggested that these correlations also are due to territorial expansion and population growth. For the tribe as a whole, all but the tightly linked markers of the MNSs and Rh complexes are approximately uncorrelated, and large departures from multiple-locus Hardy-Weinberg expectation are primarily due to substantial Wahlund variance within the tribe. There is no need to postulate a role for selection in these disequilibria.     

The Impact of Random and Lineal Fission on the Genetic Divergence of Small Human Groups: A Case Study among the Yanomama

Most of the genetic divergence that currently separates populations of Homo sapiens must have arisen during that long period when the local village (or band) was the basic unit of biological evolution. Studies of tribally intact Amerindian groups exhibiting such small-group organization have demonstrated marked genetic divergence between nearby villages. Some of this genetic radiation can be attributed to the effects of random genetic drift over time within these small demes. Some of it, however, might be better ascribed to the consequences of nonrandom genetic assortment at the time of village fission, a recurring event for such groups. Even random genetic assortment at the time of fission would lead to some genetic divergence, due to the finite size of the parent gene pool. We term the genetic consequences of random assortment the random fission effect. Routinely, village fission occurs along family lines, leading to even greater genetic divergence between the daughter villages. We use the term lineal fission effect to describe the genetic consequences of nonrandom assortment and contrast these results with those derived from random assortment.——A formal treatment of random and lineal fission effects is developed, first for the single-locus case, then for the multiple-locus extension. Using this formulation, three Yanomama fission events were examined. Fission in the Yanomama often involves a great deal of mutual hostility between the two factions, so that subsequent gene flow between the two daughter villages is minimal. The first two examples are typical of the Yanomama behavior norm, and are accompanied by a minimum of subsequent gene flow between the daughter villages. In these two cases, the observed divergence values are very large and are also very unlikely under random fission. The lineal fission effect is pronounced. The net impact of lineal fission is to reduce the effective size of the village at the time of fission by a factor of four, relative to expectation from random fission. The third example, however, involved an unusually amicable split of a village, followed by free genetic exchange between the fission products. This "friendly fission" yields an observed divergence value not much in excess of the expectation from random fission.—The long-term consequences of such fission bottlenecks in effective population size are discussed for both intra- and inter-tribal genetic diversity. It appears that the rate of genetic divergence for tribal and subtribal groups may have been somewhat greater than would be expected from classical drift arguments.     

A univariate and multivariate examination of measurement error in anthropometry

Replicate anthropometric measurements on 20 male and 22 female Eskimos were examined using analysis of variance, product-moment correlation coefficients, and canonical variates with Mahalanobis' D² distances. Analysis of variance indicated that 12 of the 16 variables could be measured comparably by two investigators. Those variables with readily defined endpoints yielded the highest correlations between the results of two anthropometrists. The multivariate analysis demonstrated a high level of discrimination between two sets of data taken on the same group of subjects. This suggests that population comparisons using data from two or more investigators could be significantly affected by measurement error.     

A Comparison of the Genetic Infrastructure of the Ye''Cuana and the Yanomama: A Likelihood Analysis of Genotypic Variation among Populations

A general procedure is described for measuring and testing population differences in gametic frequencies. The total dispersion among populations is subdivided in hierarchical fashion. The multiple-locus treatment is simply the sum of the single-locus analyses, provided gametic equilibrium obtains among the loci. In the event that gametic equilibrium does not obtain, correlations among loci need to be dealt with.—The analysis is then used to examine the genetic infrastructure of two Indian tribes from South America, the Ye'cuana (Makiritare) and the Yanomama. From historical evidence, we may identify several "clusters" of villages within each tribe. The demographic and cultural practices affecting village formation and the maintenance of peer integrity are rather different in these tribes, however, and lead us to postulate rather different patterns of genetic variation among villages. Analyses of five codominant two-allele loci, four dominant two-allele loci and two complex loci (with four codominant haplotypes each) demonstrate that Yanomama clusters are more disparate than Ye'cuana clusters, as would have been predicted on sociocultural grounds.     

Leptin,Insulin, and Obesity‐related Phenotypes: Genetic Influences on Levels and Longitudinal Changes

This study estimated the genetic and environmental determinants of plasma leptin and insulin levels and of obesity‐related phenotypes. Included in this analysis were family members from 80 families living in kibbutz settlements, who participated in two examinations 8–10 years apart. We estimated that polygenes explained 30–50% of the adjusted leptin and insulin levels and 30–70% of the anthropometric phenotypes. This study demonstrated a significant genetic influence on longitudinal changes in leptin and BMI (h² = 0.45) and small‐to‐moderate heritability estimates for changes in insulin and other obesity‐related phenotypes. In bivariate genetic analyses, we observed positive genetic correlations between leptin and anthropometric phenotypes, suggesting that shared effects of the same sets of loci account for 20–30% of the additive genetic variance in these pairs of variables. Shared genetic factors also account for 20–25% of the additive genetic variance in insulin—anthropometric pairs of variables.     

Bilirubin binding by variant albumins in Yanomama Indians

Sera of Yanomama Indians homozygous for the common albumin allele exhibited greater total effective-binding capacities for bilirubin than did sera of individuals homozygous for the Yan-2 albumin variant in the in vitro experiments described herein. Total effective binding capacities of heterozygous samples were close to those of homozygotes for AlA. Individuals homozygous for Yan-2 might experience a higher risk of bilirubin toxicity and related disorders during the neonatal period. Further studies of binding and displacement of bilirubin by competitors, such as dietary or medicinal coumarins, might help explain the existence of these polymorphisms and the significance of phenotypic differences in binding to bilirubin.     

Differences among Yanomama Indian villages: Do the patterns of allele frequencies,anthropometrics and map locations correspond?

In order to determine the degree of correspondence between sets of multivariate observations based on different kinds of traits, two new methods, derived from fundamentally different notions of “correspondence,” are adopted here and compared. Using networks or trees to represent contemporary relationships, the first method tests the similarity of the cluster or hierarchic structures implicit in two sets of data. The second approach tests the departure from perfect geometric congruence or superimposability. Computer simulation was used to generate the distributions needed for significance tests under the null hypothesis. By the first technique, we find significant correspondence among the cluster structures for geographic, allele frequency, and anthropometric data on 19 Yanomama Indian villages. The results are similar and more precise for a subset consisting of seven villages. Some of these results differ from the conclusions which would be reached with the conventional correlations based upon entries in distance tables. The direct test of congruence, used only for the data on the subset of seven villages, gives results which differ substantially from those based on cluster-structure. There are, however, similarities between the measure of congruence and the simple correlations based on entries in the distance tables. The significant correspondences observed call for some explanation. Cultural and demographic features determine the particular non-random allocation of individuals to village fragments when a village splits. These social phenomena are invoked in tentative explanation of the agreement among historical, biological, and geographic relationships of villages.     

Population structure inferred by local spatial autocorrelation: an example from an Amerindian tribal population

Spatial autocorrelation (SA) methods were recently extended to detect local spatial autocorrelation (LSA) at individual localities. LSA statistics serve as useful indicators of local genetic population structure. We applied this method to 15 allele frequencies from 43 villages of a South American tribe, the Yanomama. Based on a network of links 相似文献   

Intertribal gene flow between the Ye'cuana and Yanomama: genetic analysis of an admixed village

Genetic exchange with a neighboring village of Ye'cuana Indians had introduced two alleles, Dia and ACPa, into the Yanomama Indian Village of Borabuk. After several generations, these alleles had reached frequencies of 0.08 and 0.10, respectively. These frequencies are puzzling because they are higher in Borabuk than in the Ye'cuana village from which they were derived. Single allele estimates of ancestral proportions obtained from either of these traits are biologically unrealistic and suggest that admixture is not a good explanation for genetic variation in Borabuk. Nevertheless, multiallelic admixture models are seen to produce credible estimates of ancestral proportions and to explain a large amount of allele frequency variation in Borabuk. When these results are compared with expectations derived froma formal pedigree analysis, good agreement is seen. Comparison of single allele estimates of ancestral proportions obtained from alleles at 11 loci, with multiallelic estimates obtained from the same 11 loci and with the pedigree-derived estimates, demonstrates the superiority of the multiallelic approach.     

Serum aldosterone and protein-binding variables in Yanomama Indians: a no-salt culture as compared to partially acculturated Guaymi Indians

Yanomama Indians from the jungles of southern Venezuela and northern Brazil excreted 1 +/- 1.5 mEq of Na and 203 +/- 109 mEq of K and had low blood pressure (BP), 102/62 mm Hg). In comparison, Guaymi Indians of Panama excreted 103 +/- 50 mEq of Na and 118 +/- 52 mEq of K and had significantly higher BP (114/75 mm Hg, p less than 0.001). Elucidating the renin-aldosterone axis, total upright serum aldosterone in 34 Yanomama was high (85.6 +/- 78 ng/100 ml). The binding capacities of thermolabile (ABG) and thermostable (ABG-Ts) serum globulins for aldosterone were elevated at 23.8 +/- 6 and 14.9 +/- 2.6%, respectively; consequently, total ABG- plus ABG-Ts- bound aldosterone was as high as 38.6 +/- 6.3%. Plasma renin activity (PRA 10.3 +/- 2.4 ng/ml/h) and urinary aldosterone 18-glucuronide (70.3 +/- 30 micrograms/24 h) in 17 Yanomama were also very high. In contrast, total serum corticosteroids and corticosteroid-binding globulin (CBG) binding capacity were normal, suggesting normal ACTH activity. PRA correlated positively with total (r = 0.47, p less than 0.05) and free (r = 0.47, p less than 0.05) serum aldosterone, which in turn showed a negative trend with Na (r = 0.33, NS) excretion. The effect of high dietary K appeared less important to aldosterone stimulation and PRA suppression. ABG-bound aldosterone (r = 0.43, p less than 0.01) as well as ABG-Ts (r = 0.56, p less than 0.05) were negatively correlated with diastolic but not systolic BP. The total ABG- and ABG-Ts-bound fraction correlated with diastolic BP (r = 0.43, p less than 0.05) in contrast to the free fraction (r = 0.08, NS) or total aldosterone (r = -0.09). Apparently, only bound serum aldosterone is important for the maintenance of diastolic BP. High serum aldosterone, with elevated excretion, indicates an increased secretion rate; increased serum protein binding suggests an increased tissular activity and alterations in aldosterone metabolism. In Guaymi Indians both total plasma aldosterone (14.5 +/- 65 ng/100 ml) and urinary aldosterone (8.1 +/- 4.8 micrograms/creatinine excretion) were normal. ABG-binding capacity for aldosterone was moderately elevated (17.8 +/- 4.8) and of ABG-Ts normal (10.2 +/- 1.2) suggesting a nearly normal aldosterone metabolism and regulation. The BP of Guaymi was significantly higher than that of the Yanomama.     

Morphological variation and heritability in three Melanesian populations: A multivariate approach

In two previous papers Giles, Walsh and Bradley ('66) and Giles, Wyber and Walsh ('70) have shown that the inhabitants of three adjacent villages on the edge of the Markham Valley in New Guinea have significant heterogeneity in all blood group frequencies tested. The language, environment, culture, and ancestry of these people are essentially identical. The differences in the blood group frequencies were attributed to genetic drift and particularly to founder effect. In this paper the anthropometric data from these villages are analysed. Analysis of variance shows that 50% of the traits are significantly different. Multiple discriminant analysis demonstrates that the villages can be significantly separated morphologically. The heritability of each trait is determined using an analysis of within and among sibship variation. Traits with strong “genetic” components of variation and traits with strong “environmental” components contribute significantly to the morphological heterogeneity among the villages. Some speculations are presented on the cause of the “genetic” component of morphological variation.     

Anthropometric studies in Brazilian Cayapo Indians

Results of 16 measurements and 7 indices obtained from 130 men and 156 women belonging to three populations of Brazilian Indians are reported. For both males and females the averages for stature and head breadth are in the middle of the distribution range of values observed in other South American tribes; those for head length and nasal height are relatively low but the averages for sitting height, calf circumference and minimum frontal breadth are high. As for the indices, in both sexes the cephalic and cephalofacial are medium, the Rohrer, jugomandibularis and facial low, and the nasal high when compared with other tribes. Morphological distances between the three Cayapo populations were estimated using Mahalanobis' D² statistic; they are smaller than those separating different tribes and are not the expected ones when the demographic variables of these groups and the geographic distances between them are considered. The amount of variability as expressed by the coefficient of variation and the prevailing pattern of sexual dimorphism are similar to those observed in other Indian populations.