Differential reproductive success and body dimensions in Kavango males from urban and rural areas in northern Namibia

Abstract

We investigated differential sex-biased parental investment in relation to social status in 59 Kavango males from Rundu, the administrative and commercial center of the Kavango district in northern Namibia, and in 78 Kavango males from the rural areas around Rundu. Twenty-three body dimensions were used as indicators for the probands' social rank in the groups. The males from Rundu surpassed the males from rural areas in nearly all anthropometric features, but the urban males had significantly less offspring, especially fewer dead offspring. The association between the anthropometric variables and the number and sex of the offspring showed marked differences between the two proband groups. Although in the rural areas robust males had more children than smaller and leaner males, the taller and more robust males from Rundu had fewer offspring than smaller and more slender males. These results indicate that males from rural areas and males from urban areas follow different reproductive strategies.

PIP: The field research was conducted in various locations of the Kavango district of northern Namibia from June to September 1987. 137 healthy men between the ages of 18 and 39 years (x = 26.4 years) volunteered for this study. All probands belonged to the Southern Bantu speaking Kavango people, which can be divided into five matrilinear tribes: Kwangali, Mbunza, Sambyu, Gciriku, and Mbukushu. The present sample could be divided into two subsamples, which included members of all Kavango tribes. The first subsample comprised 59 men living in Rundu, the administrative center of the Kavango district, as wage earning employees. Their social status, Westernized nutritional habits, and physical appearance differed markedly from those Kavango living in the rural areas. The second subsample comprised 78 men from the rural areas around Rundu. They lived in traditional kraals as horticultural pastoralists, earning no regular income. 36 head and body measurements were taken directly from the subjects according to the methods of Knussmann (1988). A comparison of the anthropometric features of the two subsamples showed marked differences between Kavango males from Rundu and Kavango males from the rural areas surrounding Rundu. The Kavango males from Rundu surpassed the Kavango males from the rural areas in most of the length, breadth, and circumference dimensions of the postcephalic body. To obtain more information about the structure of the anthropometric data, factor analyses of the 23 anthropometric variables were computed for the combined sample and separately for each subsample. The males from the rural areas had more children, more sons and daughters, more dead children, more dead sons, and more living children than the males from Rundu. Statistically significant differences between the two samples occurred with total number of children (dead or alive), total number of boys (dead or alive), total number of boys (dead), total of number of children (alive), and total number of boys (alive).