Slave ships were large cargo ships specially converted for the purpose of transporting slaves. ... As many as 20 million Africans were transported by ship. The transportation of slaves from Africa to America was known as the Middle Passage.
The most important reason for the collapse of Rome was the failure to actually integrate what they conquered. When Roman soldiers conquered new lands, it was rare that they ever attempted to force their culture, ideals, or laws upon the natives and barbarians. Thus, when the Empire began suffering internal struggles, the natives they had conquered decided to take action, which lead to the swift collapse by barbarian invasion from all sides. It's hard to pick a LEAST important reason, seeing that there were many of them, but I suppose a contender would most likely be the common refusal of the Empire to even acknowledge that barbarians were rising. On the outer edges of their territory, in places like Gaul and Morocco, the Roman government was reluctant to even recognize the threat of the barbarians, thinking that even accepting that these barbarians were causing trouble would weaken their prestige in the public eye.
Currently? probably overpopulation
They exported teas<span>, </span>salt<span>, </span>sugar<span>, </span>porcelain<span>, and </span><span>spices
They imported </span>cotton<span>, </span>ivory<span>, </span>wool<span>, </span>gold<span>, and </span><span>silver</span>
