Fertility and mortality differentials among the population groups of the Himalayas

Selection potential based on differential fertility and mortality has been computed for 24 Himalayan populations classified into four groups: Himalayan populations with Asian affinities (HPA), Brahmans, Rajputs, and Scheduled Castes (Shilpkars). Irrespective of the methodology followed, the total index of selection was found to be highest (0.794) in Barbatiyas (HPA) and lowest (0.428) in Rajputs. The relative contribution of fertility component (If) to the index of total selection (It) is higher than the corresponding mortality component (Im) in all 24 groups. An analysis of correlation and regression on different components of the indices of selection performed among these 24 Himalayan populations revealed that the contributions of If in determining It are stronger than Im. Further, both If and Im are strongly associated with It and account for 76% and 67% of total variability in It, respectively. Examination of the relationship of the selection potential with the differential altitude and social categories showed a decrease in the index from high altitude to low altitude. Similarly, an inverse relationship was found between various indices and social categories. Himalayan populations with Asian affinities (HPA) in the present study reveal higher values of selection potential. Interestingly, these populations invariably reside in high altitude areas where health and communication infrastructures are poorly developed. Thus, the differential pattern of fertility and mortality among the Himalayan populations indicates that they are passing through a stage of transition, as is evident from the decrease in various selection indices. It is also apparent that groups that are less developed socioeconomically, as well as those inhabiting high altitude regions, are lagging behind in this process.     

Natural selection among Kinnaura of the Himalayan highland: A comparative analysis with other Indian and Himalayan populations

The present investigation on fertility and mortality differential among Kinnaura of the Himalayan highland is based on data collected from 160 post-menopausal women belonging to the middle and high altitude region of Kinnaur district of Himachal Pradesh (Indian Himalayas). Selection potential based on differential fertility and mortality was computed for middle-and high-altitude women. Irrespective of the methodology, the total index of selection was found to be highest among middle-altitude women (0.386) as compared with high-altitude (0.370) women, whereas for the total population it is estimated to be 0.384. It was found that the Kinnaura of the Himalayan highland showing moderate index of total selection and relative contribution of the mortality component (Im) to the index of total selection is higher than the corresponding fertility component (If). The analysis of embryonic and post-natal mortality components shows that the post-natal mortality components are higher in comparison with the embryonic mortality components among highlanders and needs special intervention and health care. The present findings are compared with other Indian tribes as well as non-tribes of the Himalayan region and other parts of the country. It reveals that this index among Kinnaura is moderate than the other population groups; among the Himalayan population, the highest was reported for Galong (It = 1.07) of Arunachal, whereas the lowest was reported from Ahom (It = 0.218) of Manipur. The correlation and regression analysis between total index of selection (It) and fertility (If) and mortality (Im) components for pooled data of populations of the Indian Himalayan states show that If and Im account for 21.6 and 29.1% variability, respectively. In Crow's total index of selection (It) along with strong association, which is significant at the 1% level, this indicates that mortality plays a greater role in natural selection in comparison with fertility among populations of the Indian Himalayas.     

Selection intensities in menopausal and permanent contraceptor women of a rural population in India

Changing fertility and mortality patterns due to socioeconomic forces have a profound effect on natural selection in human populations. The opportunity for selection was estimated in the rural population of Visakhapatnam District, Andra Pradesh, India, in 1979. A total of 1570 women were interviewed, 1544 among them had ever been pregnant. Data were analyzed to compute fertility and mortality components of the population. The index of total selection was found to be low. Selection in relation to birth control reveals that opportunity for selection is lower among women who completed their fertility by family planning methods than in women who completed their fertility by attaining menopause. Further, the results showed that differential fertility and mortality make equal contributions to the total measure of selection in both groups, whereas in developed countries like the US the mortality component contributes only a small fraction to the total index, due to improved health conditions.     

Behavior measurement and population change

Abstract

Selection intensity, as indicated by total pre‐reproductive mortality and fertility (Crow, 1958), was computed among three Indian tribal populations living in similar geographical environments—the Kolams, Raj Gonds, and Pardhans of Adilabad District, Andhra Pradesh. The Pardhans showed the greatest selection intensity, (1.1811) followed by the Kolams (0.8564) and Raj Gonds (0.7240). Pre‐reproductive mortality and infertility contributed equally to selection intensity in these tribal groups.     

Selection intensities in menopausal and permanent contraceptor women of a rural population in India

Abstract

The opportunity for selection was estimated in the rural population of Visakhapat‐nam District, Andhra Pradesh, India. The index of total selection was found to be low. Selection in relation to birth control reveals that opportunity for selection is lower among the women who completed their fertility by family planning methods than in women who completed their fertility by attaining menopause. Further, the results showed that differential fertility and mortality make equal contributions to the total measure of selection in both groups.     

Fertility and mortality differentials among the tribal population groups of Bastar District, Madhya Pradesh, India

The authors examine fertility and mortality differentials and their impact on health care and natural selection potentials among tribal populations in rural India. Data are from the Bastar District and concern 366 mothers who have completed their reproductive life span.     

Measuring opportunity for natural selection: Adaptation among two linguistically cognate tribes inhabiting two eco-situations of North-East India

BACKGROUND:

Numerous literature on the migration of Mishings point out to the fact that the Mishing and the Minyong are two culturally and linguistically cognate tribes that co-existed in the same ecology in the hills of Arunachal Pradesh. The Mishing tribe after migration, now inhabits flood-prone areas of Brahmaputra valley of Assam.

AIM:

The study aims to measure the adaptation process of these two cognate tribes inhabiting two different ecologies at present: Hills and plains by calculating the index of selection intensity by Crow’s and Johnston and Kensinger’s formulae.

MATERIALS AND METHODS:

The reproductive histories of 77 Mishing mothers of completed fertility inhabiting a flood affected village of Assam and 74 Minyong mothers inhabiting a hilly village of Arunachal Pradesh are selected.

RESULTS AND DISCUSSION:

The Minyongs show higher average fertility than the Mishings. The proportion of embryonic death is higher, and child death is lower among the Mishings (0.1661; 0.1623) than the Minyongs (0.1319; 0.2238). The index of selection due to mortality component is contributing more toward the total index of selection in both the tribes.

CONCLUSION:

The contribution of mortality component is sizeable to the total selection like many other tribes of North-East India. Higher proportion of embryonic deaths among the Mishings infers that the causes are mostly biological whereas, the higher proportion of child deaths among the Minyongs infers that the causes are mostly socio-cultural.     

Biological fitness and action opportunity of natural selection in an urban population of Cuba: Plaza de la Revolución, Havana

This paper describes the biological fitness of an urban population of Havana city, Plaza de la Revolución, which has the lowest fertility and the highest demographic ageing in Cuba. The aim is to assess the biological fitness of this community through the indexes of action opportunity of natural selection, to determine its evolutionary pattern and the influence of its socio-cultural peculiarity. Demographic data were obtained from the reproductive histories of 1200 women between the ages of 55 and 64. Data concerning mortality and surviving offspring from the first embryonic stages until age of reproduction were also collected. In order to measure the level of biological fitness two indexes were used: the Crow index of action opportunity of natural selection and the corrected index proposed by Johnston and Kensinger, which takes into account prenatal mortality. This corrected index was calculated including and excluding induced abortions in order to evaluate the contribution of these to biological fitness. When only postnatal mortality was considered, the results showed an evolutionary pattern similar to that of developed countries, based on low mortality and fertility. However, when prenatal mortality was taken into account, biological fitness decreased and the corrected index of natural selection was 4.5 times higher than when miscarriages and fetal deaths were not considered. Moreover, this corrected index was 2.65 times higher when induced miscarriages were considered, indicating the large decrease in biological fitness as a result of the current reproductive behaviour of frequent induced abortion.     

Abo blood groups and completed reproductive performance of rural Haryanavi couples: analysing measures of selection intensities

The possible differential effects of ABO blood group materno-paternal (fetal) incompatibility on completed reproductive performance were investigated on a sample of 100 couples (100 fathers and 100 mothers) from three villages in the Jind district of Haryana state, India. The average number of live births per mating couple was slightly higher for the incompatible matings (5.32) than the compatible ones (5.05). This advantage was offset by higher postnatal mortality in the former. Consequently, the average number of living children in the compatible matings (4.64) was higher than in the incompatible ones (4.18). With reference to individual ABO matings, the index of relative fertility (Irf) was the highest in A x AB followed by B x A type of incompatible matings. No decrease in live births in O x A and O x B incompatible matings was observed compared with their reciprocal compatible ones, i.e. A x O and B x O matings, as has been hypothesized in previous studies. The total pregnancy wastage was substantially higher in ABO-incompatible matings (24.59%) than compatible matings (8.45%). About 71% of the postnatal deaths took place within one year of the birth in the case of incompatible matings compared with 50% in the case of compatible matings. The study supports the hypothesis that selection is operative at the ABO locus as revealed by the measures of selection intensity. The loss of fitness in the present sample was associated with differential mortality. There were no differences in the proportions of average number of male live births in the compatible (0.55) and incompatible matings (0.58). However, in the individual mating types, there was some evidence of higher or lower proportions of male live births.     

Variability of selection opportunities with changing socio-cultural environments

Opportunity for selection has been studied against their contrasting socioeconomic and cultural backgrounds in two endogamous populations, namely, Brahmins and Jalaris of Visakhapatnam, India. Total selection was slightly higher among the better off Brahmins than in Jalaris. But a marked qualitative and quantitative variation was found in the contributing components; the fertility differential was circa 60% in Brahmins while the mortality differential was circa 60% in Jalaris according to the Crow Index. The decreased mortality differential in Brahmins suggests that this component was directly affected by the better socio-economic level and reflects on the population's transitional phase. Further, the If value fell to a half in women who completed their fertility by family planning when compared to women who completed their fertility by menopause, thus reducing the variance in fertility component in the family planning group.     

Individual fertility rate among minor tribal populations from Andhra Pradesh,India

Abstract

The Individual Fertility Rate (IFR), a measure of current fertility status in small and illiterate preindustrial societies, is estimated for five tribal populations from Andhra Pradesh, India. The Andhra tribes exhibit high individual fertility rates ranging between 49.62 ± 1.76 (Konda Dora) and 66.63 ± 3.16 (Manzai Mali) and fall in the high‐fertility category. The differences in IFR values between affinal and consanguineous couples are not significant. A direct positive relation between IFR and tribal hierarchy is observed with relatively higher IFR values recorded for socially higher‐ranked tribes in an ascending order from lower‐ to higher‐ranked groups.     

Do tribal communities show an inverse relationship between sickle cell disorders and glucose-6-phosphate dehydrogenase deficiency in malaria endemic areas of Central-Eastern India?

Tribal communities in India constitute the largest tribal population in the world. There are about 635 biological isolates (tribes and subtribes), which constituted 8.08% (about 84.3 million) of the total population of India as per the 2001 census. Out of 635 scheduled tribes (aborigines), 62 live in the state of Orissa alone forming about 10.8% of the tribal population of India. Orissa state occupies an important place, being the 3rd in rank for the highest concentration of tribal population in the country. In India, tribal communities are highly vulnerable to hereditary diseases and have a high degree of malnutrition, morbidity and mortality. The sickle cell haemoglobinopathy and glucose-6-phosphate dehydrogenase (G6PD) enzyme deficiency are important genetic and public health problems in Central-Eastern part of India. In order to map out these genetic disorders among the tribal people, a cross-section of 15 major tribal communities from different parts of Orissa was randomly screened for haemoglobin variants and G6PD deficiency. The high frequency of sickle cell haemoglobinopathy (0-22.4%) and G6PD deficiency (4.3-17.4%), with beta-thalassemia trait (0-8.5%) taking almost an intermediate position, was observed. For G6PD deficiency, hemizygous males as well as female heterozygotes and female homozygotes were detected. Twelve cases showed compound heterozygosity for sickle cell haemoglobinopathy and G6PD deficiency. There seems to be a trend towards an inverse relationship between the sickle cell allele and G6PD deficiency, and sickle cell and beta-thalassemia allele in a cross-section of malaria endemic (Plasmodium falciparum) tribal communities in Orissa. When the frequency of sickle cell allele decreases in a cross-section of malaria endemic tribal population, the frequency of G6PD enzyme deficiency and beta-thalassemia allele increases and vice versa. Natural selection had played a major role in favour of sickle cell, beta-thalassemia and G6PD mutation alleles so that they had probably evolved as a protective mechanism against the lethal effects of malaria in this part of the country. However, the calculated values of 0.074, 0.218 and 0.337, respectively, of Pearson's correlation co-efficient (r), showed no correlation between sickle cell disorders and G6PD deficiency, sickle cell disorders and beta-thalassemia, and G6PD deficiency and beta-thalassemia.     

Selection intensities and consanguineity in the Yadava and Vadabalija of Visakhapatnam, Andhra Pradesh, India.

The opportunity for intensity of selection is studied in two backward caste groups with different occupations, namely Yadava (pastoral) and Vadabalija (fishing) of Bheemunipatnam Taluk of Visakhapatnam District, Andhra Pradesh. The amount of selection intensity is found to be higher in Vadabalija (0.8583) than Yadava (0.5827). The contribution of mortality to the total index of selection is greater in Vadabalija (0.6095) than in Yadava (0.3326). When consanguineity is considered, the fertility components of selection intensity (0.1885) are lower in the consanguineous group of Yadava than in the nonconsanguineous group (0.2845), whereas in Vadabalija they are higher in the consanguineous group (0.5261) than in the nonconsanguineous group (0.2223).     

Demography of the Juang tribal population of Orissa

Demographic analysis of genealogical data collected in 1954 for 23 Juang villages was undertaken employing indirect estimation techniques and computer projection methodology. Results indicated that this group did not feature the historically high fertility levels associated with Indian tribal groups, although fertility was higher than previously reported for the Juang. The population did feature a mortality differential, with worse mortality conditions than the Indian national population at this time. Reversed sexual mortality differentials, common in South Asian populations, were also present for the Juang. Computer projection investigation revealed a steadily growing population, in contrast to some Indian tribal groups faced with extinction.     

Strategies of adaptation: interpopulation selection differentials

Spatial and temporal variation of selection intensities has been analyzed using published data on Crow's indices in 278 human populations, representing various anthropological types, religions, cultures and a wide spectrum of environmental conditions. Statistical analysis has shown that populations with different types of economy have different adaptive strategies. In tribal populations both components of selection-differential fertility and differential mortality-have equal contributions, vary according to ecological factors and show no decline with time. Urban populations of the industrially developed countries show dramatic selection relaxation; the second component becomes negligible due to a sharp decrease in childhood mortality; fertility and its variance are reducing due to cultural factors (family planning).     

Study on a Brazilian isolate. II. Opportunity for selection

The opportunity for selection, measured by prereproductive mortality and fertility, was calculated for a small and relatively isolated Brazilian population. The total index of selection opportunity (0.53) was low in comparison to those obtained for other isolated populations. The contribution of prereproductive mortality (Im = 0.28) was 40% higher than that of fertility (If = 0.20).     

Demographic study of one sedentary and two migrant populations of eastern India

Demographic data were collected from 185 sedentary Oraon of Gumla district of Bihar, 255 migrant Oraon, and 242 migrant Tamang households, covering a total population of 1009, 1414, and 1537 individuals, respectively. Both migrant groups were tea garden laborers working in the Birpara, Lankapara, and Tulsipara tea gardens in the Jalpaiguri district, West Bengal, India. The present study reveals that the migrant Oraon possess significantly higher fertility and (infant) mortality than the sedentary Oraons even though they are a genetically similar group. The study also reveals that the two migrant groups differ with respect to both fertility and mortality even though they inhabit similar physical and sociocultural environments.     

The genetic heritage of the earliest settlers persists both in Indian tribal and caste populations

Two tribal groups from southern India--the Chenchus and Koyas--were analyzed for variation in mitochondrial DNA (mtDNA), the Y chromosome, and one autosomal locus and were compared with six caste groups from different parts of India, as well as with western and central Asians. In mtDNA phylogenetic analyses, the Chenchus and Koyas coalesce at Indian-specific branches of haplogroups M and N that cover populations of different social rank from all over the subcontinent. Coalescence times suggest early late Pleistocene settlement of southern Asia and suggest that there has not been total replacement of these settlers by later migrations. H, L, and R2 are the major Indian Y-chromosomal haplogroups that occur both in castes and in tribal populations and are rarely found outside the subcontinent. Haplogroup R1a, previously associated with the putative Indo-Aryan invasion, was found at its highest frequency in Punjab but also at a relatively high frequency (26%) in the Chenchu tribe. This finding, together with the higher R1a-associated short tandem repeat diversity in India and Iran compared with Europe and central Asia, suggests that southern and western Asia might be the source of this haplogroup. Haplotype frequencies of the MX1 locus of chromosome 21 distinguish Koyas and Chenchus, along with Indian caste groups, from European and eastern Asian populations. Taken together, these results show that Indian tribal and caste populations derive largely from the same genetic heritage of Pleistocene southern and western Asians and have received limited gene flow from external regions since the Holocene. The phylogeography of the primal mtDNA and Y-chromosome founders suggests that these southern Asian Pleistocene coastal settlers from Africa would have provided the inocula for the subsequent differentiation of the distinctive eastern and western Eurasian gene pools.     

Opportunity for natural selection in a Basque population and its secular trend: evolutionary implications of epidemic mortality

Analysis of the interaction between mortality patterns and opportunity for natural selection could help to elucidate potential evolutionary implications of epidemic mortality. In this paper secular trends are studied in relation to Crow's index (It) and its components of mortality (Im) and fertility (If), using parish records for family reconstitution in a Basque population. A principal components analysis (91% of the variance accounted for) showed marked quantitative and qualitative variations of Im and If depending on the stage of demographic transition of the population analyzed: In pretransitional societies the opportunity for natural selection is determined mainly by differential prereproductive mortality, whereas in posttransitional societies selection resulting from differential fertility plays a key role. The highest values for the mortality component (range 0.81-1.26) and for the relative contribution of Im, to It (range 47.1-57.2%) were observed in periods with a high incidence of infectious diseases and when the most severe mortality crises were detected (1830-1859, 1860-1889, and 1890-1919). A differential incidence of epidemic mortality was also found at prereproductive ages (before 16 years) and at reproductive ages (16-45 years), which provides strong support for the idea of the long-term genetic consequences of mortality crises.     

Biosocial covariates of adult male body mass index in Central India

Body mass index (BMI) is the 'measuring rod' of nutritional status. This study investigates the type and extent of correlation between adult male BMI and socioeconomic, cultural and bio-demographical variables using data from 11,496 individuals from 38 districts of Central India. For each individual, stature, body weight and sitting height data were collected, their Cormic index and BMI computed, and averages for each district calculated. Mean BMI was found to be lowest for the population of Tikamgarh (17.90+/-1.91 kg m(-2)) and highest for that of Durg district (19.33+/-2.16 kg m(-2)), whereas the mean BMI for the total population of Central India was 18.67+/-2.18 kg m(-2), which is lower than that of well-to-do individuals in India as a whole. The F ratio indicates that there is inter-district variation in anthropometric characteristics of populations. District-wise biosocial indicators were obtained, namely population density per square kilometre, percentage urban population, percentage of population that is of scheduled caste/tribe, sex ratio, average rural population per PHC/CHC (primary or community health centre), literacy rate, life expectancy, total fertility rate, infant mortality rate, gender development index and human development index. Most of these variables were found to be significantly correlated with each other, but BMI was only significantly correlated with three of them, viz. gender development index (R2=0.211), life expectancy (R2=0.130) and infant mortality rate (R2=0.128). Gender development index and life expectancy were positively correlated with BMI, whereas infant mortality rate was negatively correlated. It is concluded that if BMI increases then life expectancy will also increase. Thus better nutritional status may be a helpful tool for reducing infant mortality rate, which is an indicator of socioeconomic status, health condition, health care and ultimately overall development of a region or population.