Inbreeding effects on the growth in stature among Telaga boys and girls of Kharagpur, West Bengal, India.

The present study is an attempt to understand the genetical effects of inbreeding on the process of growth. The inbred and non-inbred subjects were selected on the basis of extensive pedigrees of five generations in the Telaga, an endogamous population of Kharagpur, India. Preference was given to cousins belonging to the same kindreds while selecting control sample so that environmental variation was minimized. Altogether 633 boys and 614 girls of different inbreeding levels aged five to twenty years were measured for stature. Analysis has been done in different levels of inbreeding in each age and sex on mean annual increments and variances of increments. The results revealed that comparison of annual increment for each age between boys and girls with different degrees of inbreeding and application of the one-tailed t-test of significance does not provide any evidence of inbreeding effect on mean increment for stature studied in either sex. This might indicate the absence of marked dominant/recessive effects of genes determining annual increments in body size rather than the absence of genetical control of increments due to growth. Moreover, it is noteworthy that the variance of annual increment due to growth (which is estimated indirectly) consistently increases with increase of inbreeding level with only a few exceptions. The exceptions occur more often in girls than in boys, which can be explained by greater environmental stress and selection pressure and variation in X-linked inbreeding among girls. This would be worthwhile to verify in longitudinal growth data in future. Increased variances of annual increment with inbreeding, in the absence of change of mean increment on inbreeding, would indicate the influence of additive autosomal genes for the process of physical growth in children in either sex. A close scrutiny of the annual increments for the measurements in all the four levels of inbreeding in either sex fails to bring out any consistent trend of change in the age of adolescent spurt with inbreeding. This might suggest an underlying homozygosity of several genes with inbreeding in the population.

Inbreeding depression in anthropometric traits among Telaga boys of Kharagpur, West Bengal, India.

Inbreeding depression in phenotypic variations as well as reproductive capacity was reported in animals. Depression of physical measurements in human beings especially among infants and adults due to inbreeding has also been reported all over the world. The present study is an attempt to examine the nature of inbreeding effect on growing children at each yearly age with increase of inbreeding intensity in a local endogamous population based on pedigree data. In general, mean values of measurements appear to be smaller in higher levels of inbreeding from that of lower levels of inbreeding in each yearly age. These differences are even more marked when grouped as low and high inbreeding level. The percent of inbreeding depression tends to be larger in post adolescent boys than in younger children.