In my last post, I argued against the view that black slaves were numerically insignificant outside sub-Saharan Africa until the rise of Islam in the 7th century. It looks like black slaves began to enter the Middle East in growing numbers some time before 0 AD, the result being a slow but steady increase in the region’s black population throughout the early Christian era and into the Islamic era.
I will now discuss the origins of the black slave trade in terms of its causation. This subject has generally been approached from the demand side, i.e., the Muslim world and later the European world. Here, I will focus on the supply side. What causes, internal to sub-Saharan Africa, tended to create slaves in excess of local demand?
The question may seem incomprehensible to many. It is widely assumed that sub-Saharan Africans were enslaved because they were politically and militarily helpless in the face of European or Arab outsiders. Yet before the 19th century most black slaves were purchased peacefully at trading posts on the periphery of sub-Saharan Africa, either on the coasts or in the Sahel. They were procured from indigenous middlemen, who in turn procured them from indigenous sellers.
A more nuancé view holds that these indigenous agents enslaved their fellow Africans in response to rising demand outside Africa for black slaves, particularly on New World plantations from the 17th century onward. Nonetheless, there is evidence from earlier periods that some sub-Saharan societies were already generating slaves well in excess of their own needs. When Portuguese traders reached the Niger delta in the late 15th century they were able to purchase large quantities of slaves from indigenous sellers. This trade, at least in its initial stages, seems to have been supply-driven rather than demand-driven.
Who were these slaves? Overwhelmingly, prisoners taken in war. Although historians agree that endemic warfare was linked to the slave trade, they are less sure about the direction of cause and effect. Did the slave trade provide an incentive for warfare—as a way to get the wherewithal with which to buy foreign goods? Or did warfare provide an incentive for the slave trade—as a way to get rid of unwanted prisoners of war? The former view was propounded by abolitionists and is still popular, witness this Wikipedia article:
Enslavement became a major by-product of war in Africa as nation states expanded through military conflicts in many cases through deliberate sponsorship of benefiting Western European nations.
Yet, further on, the same article states:
The practice of enslaving enemy combatants and their villages was widespread throughout Western and West Central Africa, although wars were rarely started to procure slaves. The slave trade was largely a by-product of tribal and state warfare as a way of removing potential dissidents after victory or financing future wars.
Clearly, European traders benefited from the warfare that occurred endemically throughout sub-Saharan Africa. But they were at most an auxiliary cause. If we exclude hunter-gatherers, all sub-Saharan societies had warrior castes that predated European contact and encompassed all unmarried men. Although militarization of single males has equivalents in most cultural areas, it had a greater impact in sub-Saharan Africa because enforced bachelorhood lasted much longer and affected virtually all young men.
African men stayed single longer because so many women were siphoned off by older, high-status males. Generally 20-50% of all marriages were (and often still are) polygynous in sub-Saharan agricultural societies (Bourguignon and Greenbaum, 1973, p. 51; Goody, 1973; Pebley and Mbugua, 1989; Welch and Glick, 1981; White, 1988; see Figure 1). Year-round agriculture made women largely self-reliant in feeding themselves and their children, thus letting more men take second wives. More polygyny for some, however, meant no wives at all for others. Usually the wife shortage was resolved by raising the age of marriage for men. For instance, among the Nyakyusa:
There is no evidence of any marked difference in the survival rate of males and females, but there is a difference of ten years or more in the average marriage-age of girls and men, and it is this differential marriage-age which makes polygyny possible. (Wilson, 1950, p. 112)
Raising the marriage age, however, simply concentrated celibacy in one age group. For these young men the only way to get a woman was to abduct one through warfare. Indeed, although the decision to wage war usually lay with older, married males, the warfare itself was more easily initiated and pursued because young males saw it as the best means to become sexual, reproducing beings, i.e., ‘real men.’ The stresses created by this situation are described by Pierre van den Berghe (1979, pp. 50-51):
Typically, the more men are polygynous in a given society, the greater the age difference between husbands and wives. … The temporary celibacy of young men in polygynous societies is rarely absolute, however. While it often postpones the establishment of a stable pair-bond and the procreation of children, it often does not preclude dalliance with unmarried girls, adultery with younger wives of older men, or the rape or seduction of women conquered in warfare. Thus, what sometimes looks like temporary celibacy is, in fact, temporary promiscuity. These young men often devote themselves to warfare during their unmarried years and sometimes homosexuality is tolerated during that period.
There is a large body of literature, called Youth Bulge Theory, that relates the probability of war to the proportion of young single males in the population (Mesquida and Wiener, 1996; see also Wikipedia –War). This proportion is at its highest where the polygyny rate exceeds 20% of all marriages—mostly in the agricultural societies of sub-Saharan Africa and Papua-New Guinea.
In such regions, this internal social contradiction could be resolved by externalizing it, i.e., by abducting women from adjacent peoples through warfare and by selling off any male captives.
Bourguignon, E. and Greenbaum, L.S. (1973). Diversity and Homogeneity in World Societies, HRAF Press.
Goody, J. (1973). Polygyny, Economy and the Role of Women, in J. Goody (Ed.) The Character of Kinship, Cambridge: Cambridge University Press, pp. 175-190.
Mesquida, C. G. and Wiener, N.I. (1996). Human Collective Aggression: A Behavioral Ecology Perspective, Ethology and Sociobiology, 17, 247-262
Pebley, A. R., and Mbugua, W. (1989). Polygyny and Fertility in Sub-Saharan Africa. In R. J. Lesthaeghe (Ed.), Reproduction and Social Organization in Sub-Saharan Africa, Berkeley: University of California Press, pp. 338-364.
van den Berghe, P.L. (1979). Human Family Systems. An Evolutionary View. New York: Elsevier.
Welch, C.E., and Glick, P.C. (1981). The incidence of polygamy in contemporary Africa: A research note. Journal of Marriage and the Family, 43, 191-193.
White, D. R. (1988). Rethinking polygyny. Co-wives, codes, and cultural systems. Current Anthropology, 29, 529-572.
Wilson, M. (1950). Nyakyusa kinship, in Radcliffe-Brown, A.R., and Forde, D. (Eds). African Systems of Kinship and Marriage. (pp. 111-139), London: Oxford University Press.