Population structure of the Indian people: some microevolutionary aspects.

Some aspects of population structure, namely village endogamy, marital distance and consanguinity in India are discussed. These parameters show social and geographic variation. The role of culture is of great importance in determining the mating pattern of a population. In the Indian situation, group endogamy in general does not cause inbreeding. Consanguinity is a cultural phenomenon of long-standing tradition, and so far there is no strong indication of a temporal change.

PIP: This study analyzed the role of India's population structure in influencing genetic composition under different sets of conditions, including marital distance, village endogamy, and consanguinity. Mean marital distance (distance between the birthplaces of spouces) varies widely for different Indian populations, from 8.5-95 km, and is largely influenced by whether village endogamy is encouraged or discouraged. Thus, the particular situation of a caste group produces different forms of gene dispersion. In general, group endogamy does not cause in inbreeding. Consanguinity is a longstanding cultural tradition, with geographical location rather than caste playing the decisive role in influencing mating patterns. There is no evidence of a temporal decrease in consanguinity. The different patterns of gene dispersion and mate selection in India necessitate prior knowledge of the social structure when planning and interpreting genetic studies.

Opportunity for natural selection among the Indian populations.

A critical review of data on opportunity for natural selection among the Indian populations has been made. These data on 96 populations were analysed according to regional, habitat, and socioeconomic backgrounds. The trends observed on the basis of these Indian data have been compared with worldwide data and data from industrialized nations. As in the industrialized nations, a gradual decrease in I(m) and I(t) is observed with improving socioeconomic and technological status in the Indian populations. The Indian situation is similar to that of the first phase in the modern demographic transition among the industrialized nations.

[Quantitative dermatoglyphic markers in fra-X-syndrome]. / Untersuchungen quantitativer Hautleistenmerkmale beim fra-X-Syndrom.

Quantitative dermatoglyphic characters of fingers and palms of 61 male patients with fra-X-syndrome and 20 female heterozygote carriers were analysed and compared with the data from 84 male and 90 female normal individuals. Univariate and multivariate analysis of the data led to the following conclusions: 1. The fra-X-syndrome patients show higher ridge count and higher MLI value (increased transversality of the main lines), and lower a-b ridge counts than the controls. In addition to this, differences are observed also for the diversity and asymmetry measures. 2. Discriminant analysis as applied to the sexes separately, showed that 75% of males can be correctly classified in their group. However, the percent of correctly classified females is lower than the males; it is 70% (fra-X female) ad 64.4% (control female). 3. D2-matrix and the comparison of TFR C values support the hypothesis of X-chromosomal doses effect on the dermatoglyphics.

[Estimation of the heritability of hair and eye color]. / Schätzungen der Heritabilität von Haar- und Augenfarbe.

In the present study the colours of hair are regarded as quantitative genetic characters. The genetic and environmental components of the total variance of the characters are determined by analysis of correlation between parents and children as well as full sibs. An analysis of correlation coefficients makes it possible to further examine whether autosomal dominance or X-linked factors play a role in the inheritance. The correlations between the parents make the genetical analysis more complicated as they raise the correlation coefficients between relatives. The estimates of heritability are 0.61 (hair-colour) and 0.80 (eye-colour). These estimates may serve as preliminary values of orientation. Only further studies will show whether the relative large part of the variance caused by the environment can be confirmed. Dominance may play a small role in the case of hair colour, while it seems to be absent in eye-colour. There are no sufficient indications of X-linked factors for both characters.

A comparison of dermatoglyphic methodologies in population studies.

Use of dermatoglyphics in population studies has been marked by a great deal of methodological variation among investigators. We compare various dermatoglyphic approaches using data derived from four groups in the Kumaon region of India. Dermatoglyphic data included ridge-counts and other quantitative variables, and the classification systems of Cummins and Midlo and Penrose and Loesch. Results were evaluated against anthropometric and serological relationships. No clearly superior approach emerges, although it is generally true that palmar variables exhibit more intergroup heterogeneity than digital variables and produce more reasonable results than the other approaches. The conventional method of treating ridge-counts, that of choosing the larger of the two counts, was the most unsatisfactory of the quantitative approaches, leading to the recommendation that both radial and ulnar counts be retained. We conclude that environmental variation may contribute substantially to intergroup variation.

Biological affinities between migrant and parental populations of fishermen on the east coast of India.

We examined biological affinities between the migrant groups of fishermen in Puri and their parental counterparts using 3 sets of variables: genetic markers, anthropometric measurements, and quantitative dermatoglyphics. Results of both univariate and multivariate analyses suggest a significant migration effect, diversifying migrants from their parental populations, although the distance configurations based on each set of variables resemble each other. The migration effect is particularly remarkable for the anthropometric measurements. The plot of group centroids based on the discriminant analysis of the 7 populations depicts a clear segregation of migrants from the parental populations. Because of relatively large effective population sizes and short history of these populations in Puri, the role of genetic drift can be safely ruled out. However, a founder effect is a plausible reason for the observed differentiation of the migrants from their parental groups, especially given that certain rare variants that were not observed in the parental populations appear in the migrants. That the founders were a select group of fishermen with respect to body dimensions, not a random group, can be inferred from the occupational differences among the migrant groups, which in turn suggests phenotypic plasticity in the observed differentiation. Regression of mean phenotypic variance and heterozygosity on the distance from the centroid suggests a strong possibility of external gene flow into the migrant populations in Puri.

Opportunity for natural selection with special reference to population structural measures among the Vadde.

Crow's indices of opportunity for natural selection have been studied among the Vadde, a fishing community of Kolleru Lake, Andhra Pradesh, India. The sample comes from 15 of the 60 fishing villages. The indices were computed both at the level of village and population units. A village sample of Palle, another fishing group in the area, has also been analysed for the purpose of comparison. An attempt has been made to explain variation in selection indices among the villages using population structural measures. A wide variation is found in both the fertility and mortality indices between the villages. The values were compatible with those found for other fishing groups studied previously, and in the middle of the range observed for the Indian populations (about 100) studied so far. Population structural measures are found to explain a significant amount of variation in Im and It but not in the fertility index.

Biological affinities between the migrant groups of fishermen of Puri Coast, Orissa, India.

Biological affinities between the three endogamous groups of marine fishermen of Puri are examined with the help of nine anthropometric measurements and 22 dermatoglyphic traits of fingers and palms. The results are interpreted in the light of their ethnic, geographical, and migrational backgrounds. Multiple discriminant analysis and Mahalanobis's generalized distances suggest higher discrimination of populations with reference to anthropometric traits as compared to that in dermatoglyphic variables. While the nature of interpopulation distances conforms to the geographic pattern in anthropometrics, no clear picture emerges in the dermatoglyphic distances supporting either ethnic or geographic evidence.

Variation in hair histological variables: medulla and diameter.

Two hair histological variables, the incidence of medullation and diameter, have been dealth with in twelve populations belonging to different ethnic groups and living in different geographical areas. Results of the F test comparing within-individual variance, between-individual variance and between-population variance of the hair variables concerned indicate that differentiation of various populations is possible. Sex differences for medulla and diameter of hair are observed in some populations included in the present study.

Quantitative palmar dermatoglyphics and the assessment of population affinities: data from marine fishermen of Puri, India.

Variation in quantitative dermatoglyphics among three endogamous groups of marine fishermen of Puri Coast, India, is greater for the palmar variables than for the fingers. This is the case in both the sexes. The pattern of population affinities, however, differs for the males and females. In order to evaluate the importance of palmar variables in population studies, the results in males are compared with those of finger variables and anthropometrics. There is no significant heterogeneity between the groups for finger variables. Although significant intergroup variability is observed in the palmar and anthropometric traits, the two sets of results are not in the same direction. Palmar dermatoglyphic relationships reflect the caste affiliations, while the anthropometric are in line with geographic proximity.

Genetic differentiation among four groups of fishermen of the eastern coast, India.

The four endogamous groups of fishermen living around the city of Puri, located on the eastern coast of India, were studied for blood groups, red cell enzymes and serum proteins (11 loci). Only 1.3% of the total diversity among the groups studied is due to differences between them (GST = 0.013). The genetic distances between populations were estimated using Edwards and Cavalli-Sforza's method. The pattern of genetic distance reflects the geographical distribution of these groups. In general, these observations support the patterns of variation based on anthropometric and dermatoglyphic variables.