120 Françoise Latour da Veiga Pinto,
A. Carreiraof Prince Henry, instigator of the African expeditions. The choicest slaves had
previously been offered to the Church.
From this time on, slave trading came to be regarded both as a means of
providing a commodity exportable to Spain and Italy and as a source of domes-
tic and agricultural labour for Portugal itself. The latter aspect became increas-
ingly important during the fifteenth and sixteenth centuries, as Portugal's
expansion called for more and more manpower. At that time Portugal had a
population estimated at only around 1.5 million. Men who went to sea or
settled in the colonies needed to be replaced; and Negro slave labour met this
need. A third factor very soon came into the calculation when it was realized
how useful the blacks were for sugar cultivation. This commodity, still extremely
rare, had been introduced into Europe by the Arabs. Attempts had been made to
grow it in Portugal itself, in the Algarve, but with only very limited success
because it took too much out of the soil. The discovery of the Atlantic islands,
however, was to bring about the rise of the sugar-cane industry and pave the
way for the introduction and development of its corollary, the Atlantic slave
trade.
The Spaniards had earlier introduced sugar cultivation into the Canary
Islands, using the Guanches as slaves. Prince Henry, who had been granted by
the crown a trading monopoly for the newly discovered territories, followed
their example in Madeira and the Azores. The Negroes turned out to be more
docile as labourers than the Guanches, and were very soon being re-exported
from Portugal to the islands. Demand grew rapidly in consequence, compelling
the traders to introduce a less 'primitive' method of acquisition than kid-
napping. They had quickly realized that the filhamento system was excessively
bad for trade : for the coastal peoples had soon learnt to beware of ships, and
avoided going on to the beach so as not to be taken prisoner. The traders
therefore sought to establish normal trading relations on a barter basis; and
for this they very early used the first captives as interpreters. The role of the
latter was very important for the development of the trading system. The
Venetian Cá da Mosto, employed in the service of the Portuguese crown,
records that some slaves, once they had been baptized and could speak their
masters' language, were put aboard caravels and sent back among their kins-
men: they then became freed men when they had brought in four new slaves.
They also furnished valuable information, both geographical—e.g. about
deposits of precious metals—and commercial, such as lists of goods in demand
among the natives, and their habits and customs. Once the Portuguese realized
that they could acquire slaves by a peaceful exchange of goods which the chiefs
and their go-betweens were avid for, a regular trade began to operate. There
was, after all, a meeting of supply and demand : for slavery formed part of
the social system among the peoples of Senegambia and Guinea, and it was
normal to sell one's own kind if they were prisoners of war or were under