...or at the very least, was greatly diminished or insignificant compared to what actually happened over the course of four centuries?
Using wage labor and indentured servitude of people mostly of European descent (with some Africans and Native Amerindian peoples), how would this have affected the immediate economies of the colonies established by the Kingdom of England (later as the United Kingdom of Great Britain), the Crown of Castile (later as Habsburg and then Bourbon Spain), the Kingdom of Portugal, the Kingdom of France (later as the French Republic), and the Dutch Republic (or better yet, the Republic of the Seven United Netherlands)? Would resources like sugar cane and cotton have been as profitable and their industries as widespread as they became without black slaves?
How would this affect the culture of the United States, whose African American community has been responsible for so many cultural innovations such as the inventions of jazz, blues, rock n' roll, and soul music?
There would arguably be no president called Barack Obama. For that matter, the ethnic minorities of various people of African descent would probably represent a much smaller portion of the population today. They would also probably have firmer roots and family ties back home with the African nations they came from, much like some African immigrants to the United States today.
Without the Atlantic Slave Trade, would the European powers have colonized Africa to the extent that they did, as well? Of course they would colonize to the extent that small settlements in the interior would be built for the purpose of extracting precious resources like diamonds. However, if Africa remained largely undeveloped (minus Berber North Africa, Egypt, and Ethiopia of course), would the African nations we see today have even come into being?
I give the floor to you, ladies and gentlemen.