The slave traac
and the Atlantic economies 1451-187069particularly on the sugar-cane plantations, etc., actually led to rates of net natu-
ral decrease among the slave populations. Since rates of net natural decrease
did not operate in the African territories from which people were exported,^42 the
only usable rate is that among the Africans in North America. For this terri-
tory, Professor Curtin's calculations show that about 430,000 Africans imported,
largely between 1700 and 1810, produced a black population of about 4.5
million by 1863.«
Before this rate of reproduction can be refined to provide a rough approxi-
mation of the numbers that would have been reproduced in Africa by the people
exported, some qualifications are necessary. The North American imports
were concentrated in the second half of the eighteenth century so that it actually
took the 430,000 imported Africans very much less than a century to produce
a population of 4.5 million by 1863. By the time a large number of Africans
began to arrive in North America in the second half of the eighteenth century,
the first million people to leave Africa as a result of the external slave trade
in all its sectors had done so for more than 100 years. On the other hand, the
harsh conditions of slavery, its psychological effects on the fecundity of female
slaves and the strange disease environment still reduced to some extent the
rate of reproduction among the imported Africans in the United States.
On the other side of the coin, it may be argued that the mortality rate
in tropical Africa during our period was higher than that of North America
during the same period. If this was the case, then the survival rate among the
children of Africans in North America, from about the second generation
onward, would be higher than that in Africa. In addition the slaves in North
America did receive some modern medical attention, however minimal the
effect may have been on their health. Another consideration is the fact that
the population of Afro-Americans in 1863 was produced with the input of
some white fathers. It has been shown that the proportion of mulattos in the
total slave population of the United States of America in 1860 was 10.4 per
cent.^44
When these two sets of opposing factors are matched it is not easy to
decide the direction of the net result. To be conservative let us assume that,
notwithstanding all the points made above, the reproduction rates which
prevailed among the Africans imported into North America were higher than
the rates that would have prevailed among the 19 million Africans exported
had they been left in Africa. Let us even assume that, when all the facts stated
earlier have been considered, only 50 per cent of the North American rates
would have prevailed in Africa. Applying this rate to the 19 million earlier
estimated, the result is that had those Africans not been exported they would
have produced an additional population of at least about 99,420,000 in Africa
by about 1870. This calculation does not take into account the fact that the
large number of Africans who were exported several years before North