The demographic effects of the slave trade are some of the most controversial and debated issues. Tens of millions of people were removed from Africa via the slave trade, and what effect this had on Africa is an important question. Walter Rodney argued that the export of so many people had been a demographic disaster and had left Africa permanently disadvantaged when compared to other parts of the world, and largely explains that continent's continued poverty. He presents numbers that show that Africa's population stagnated during this period, while that of Europe and Asia grew dramatically. According to Rodney all other areas of the economy were disrupted by the slave trade as the top merchants abandoned traditional industries to pursue slaving and the lower levels of the population were disrupted by the slaving itself. Joseph E. Inikori argues the history of the region shows that the effects were still quite deleterious. He argues that the African economic model of the period was very different from the European, and could not sustain such population losses. Population reductions in certain areas also led to widespread problems. Inikori also notes that after the suppression of the slave trade Africa's population almost immediately began to rapidly increase, even prior to the introduction of modern medicines. Shahadah also states that the trade was not only of demographic significance, in aggregate population losses but also in the profound changes to settlement patterns, epidemiological exposure and reproductive and social development potential. J.C. Anene in “Slavery and the Slave Trade” notes that there can be no doubt that the slave trade depopulated vast areas of Africa.
It has been calculated that the European slave trade in the Atlantic was responsible for the removal from Africa of at least 12 million Africans; this without reckoning those who perished in the process. The small populations of East and Central Africa today, (areas that were subjected to slaving from Antiquity), must be accounted for by the enormous number of slaves who were captured and exported. Central Africa is one of the most sparsely populated of the inhabitable areas of Africa. In 1976 it averaged about 6 people to the square kilometer i.e. about 1/6 of the population density found in the wooded areas of West Africa. Central Africa has no great concentrations of the rural population such as occur on the Niger Delta in West Africa. This is because of the extensive slave trading in this region in pre-colonial times, which had enormous ramifications for the lives of the local populations.
Case Study: Angola: The history of Portuguese Africa is synonymous with the slave trade. Angola’s history in particular has been scarred by the slave trade. It is estimated that from 1580 to 1836 over 4 million Africans were exported from the region of Congo and Angola, and over 3 million from Angola alone. J.C. Miller estimates the Mbundu’s demographic losses due to Portuguese wars and the accompanying slave trade at 10,000 slaves a year. This figure is based on early 17th century estimates of both the Portuguese and the Dutch of the slaves that left Angola every year. David Birmingham, however, argued in 1981 that a reassessment of the Atlantic Slave Trade, and in particular of the numbers that landed in Latin America (Brazil), suggests that it is unlikely that such a level was consistently maintained at this time. He posits that an average of 5,000 slaves per year seems more probable. However, it is also a fact that Birmingham’s use of statistics of slaves that landed in Latin America alive led him to under-estimate the numbers captured and shipped in Angola because he failed to take into account losses during the dreaded Middle Passage. Nevertheless, whether the figure was 10,000 per year or 5,000 per year, it still represented a major drain on the Mbundu society whose total population is unlikely to have exceeded ½ a million. West Central Africa’s demographic loss through the slave trade was therefore extremely high, perhaps proportionately higher than in any other zone of the Atlantic Slave Trade.
The loss was moreover accentuated by other factors
It was concentrated among the younger element of the population since slave merchants primarily valued men and women under the age of 30
Since the Portuguese wars of conquest were the direct source of supply, the major drain was from the Central Mbundu region (the Ngola state).
The slave trade was not the only demographic drain on Angola; there was also a growing series of refugee migrations which may have played as large a part as the slave trade in reducing Angola from the rich and populous country witnessed by the 16th century Jesuits, to the sparse desert regions described by 17th century observers. In the 16th century the slave trade also spread to the Kingdom of Kongo where it was equally harmful.
The Trans-Atlantic slave trade deserves examination in some detail because it was the most decisive factor in forming the history of Angola, earning that country the dubious title of “Black Mother of the New World”. In about 300 years some 3 million slaves were shipped from Angola, mainly to Brazil (50%), the Caribbean area (30%), and the River Plate Basin of South America. This is cited as the main reason why Angola’s population in the 1970s was only about 6,5 million, whereas normal growth predictions would have indicated a figure nearer 30 million by the 1970s. Even after the end of the slave trade and the establishment of formal colonial rule over Angola and Mozambique, Africans continued to be considered primarily as slaves, naturally inferior to the White man, and fitted for manual labour. The forced labour system introduced in Angola and Mozambique during the colonial period was in effect a ‘modern slavery’.
Similarly, in East Central Africa Swahili Arabs and the Portuguese slave traders and their African allies the Chikunda, purchased large numbers of slaves from Malawi, Mozambique, Eastern Zambia and from societies along the Zambezi as far as northwestern Zimbabwe in the 19th century. For numbers of slaves exported from this region and effects on the northern regions of Zimbabwe bordering the Zambezi, see G.T. Ncube, “The Dynamics of Portuguese Slave Trading Along the Zambezi in the 19th Century” pages 12-16.