The Atlantic Slave Trade had an overwhelmingly negative impact on the continent of Africa, particularly in the west. The only possible positive outcome that can be discussed is that certain clans and kings in the region benefited economically and politically by collaborating with the European slave traders. They were given guns in exchange for slaves, which gave them a technological advantage over their rivals. The Kingdom of Benin is the greatest example of the positive impact of European goods that were exchanged for slaves.
The demographic impact on Africa was probably the biggest negative effect. While it is difficult to pinpoint the exact number of slaves taken across the Atlantic Ocean, a rational guess puts the total at around twelve million. Between 1750-1950, the population of Africa as a percentage of the world population declined during every 50 year interval. A majority of this number were healthy, young males. This left a serious void for all military and economic activities in Africa. While some kings benefited from the trade in human cargo, most of the fragile local economies were devastated.
The slave trade was also a deadly business for Africans. It is difficult to find an exact number of people that died as a direct result of the slave trade. It is estimated that ten percent of slaves that were sent across the Atlantic Ocean did not survive. Disease and warfare associated with the slave trade also accounted for staggering death counts.
The slave trade in Africa also set a precedent for future European countries to exploit the continent for natural resources during the imperial period. Africa, which had been weakened militarily, was unable to stop the process of European colonization of the their continent in the middle to late 19th Century.