The Senegal river basin is a fuzzy dividing line between the Sahel and savanna south of the Sahara Desert and the thicker rainforests of Gambia, Guinea and Ghana. In the 8th century, the Senegal was visited by new traders and religious pundits, those that were carrying the message of Islam. This was a message that was received well by some groups south of the Sahara, notably the Fulani, who had come from Morocco and the east in the 5th century (not all the Fula peoples, but we'll get to that in a bit). The encroachment of Islam was slow; took centuries, but it was steadily clear by the 15th century that most of the people north of the jungle were largely Muslim, while most of those south of the savanna had remained animists.
Like every other part of the world, west Africa was in a state of continuous empire building. It has only been in the last fifty years that we are getting a clearer picture of what the south Sahara was like in the hundreds of years before the Europeans came. On the savanna, the Ghana Empire was followed by the Sosso, the Kanem, Mali, the Songhai and the Bamana Empires.
In the forests were the Akan Kingdoms, the Yoruba, Dahomey and Benin. These empires and kingdoms rose and fell, they attacked one another, they battled one another - in short, they did their best to exterminate each other. Just like humans did everywhere.
Then the Europeans came.
Now, I'm not interested in the modern world here, so I'm only going to talk about the first few centuries of European interest. In terms of territory, that would amount to very little. The Europeans did not fare well away from the coast in Africa. Unlike South America, the biology of Africa is far more diverse and far, far older (remember that most of the American environment is comparatively more recent, not only in terms of humans but in terms of most animal species there). Africa is thick with little buggies, successfully overcome by countless generations of Africans, just waiting to kill soft white Europeans. The Europeans in America may have brought smallpox to the natives, but Africa had dysentery, typhoid, blackwater fever and trypanosomiasis, all waiting to destroy would-be adventurers well into the 19th century, if the well-prepared natives didn't kill them first.
As such, the Europeans clung to the coastline. Portugal, France and England favored the lower Senegal, Gambia and Casamance valleys; the Dutch, Danish and Spanish - along with other French and English - favored the Ivory, Gold and Slave coasts (truth in advertising). There they did a lively trade, very much in slaves.
While once upon a 1970s a group of Hollywood producers envisioned white people catching Kunte Kinte with nets, chasing black people through the jungles like animals, the bargaining was a much colder affair. If the Yoruban animists of the forests fought Mande Islamists hundreds of miles to the north and won, they would bring their captured Muslim prizes south and sell them at places like Fort Anthony, Acra or Caran. And if the Mande won, they'd take their animist prizes west and sell them at places like Goree, Ziguinchor and James Island. And because the Europeans could sail all around the coast from Nigeria to the Canaries, they were ready to pay for whatever the market could provide.
|Note how the Europeans conceive of the long river that easily|
shuffles the slaves along the Islamic corridor ("Negroland"), where
the river conveniently splits into the Senegal, Gambia and Casamance
all at the same time.
This is why the slave trade went so well for the Europeans. As far as gathering slaves, they needed only to build a fort on the coast and wait for other black tribes to bring in their enemies. It should be remembered that whatever horrors the Europeans committed (and those horrors were far, far greater than the greed of black African traders), it was blacks that made the trade possible in the beginning.
The trade was made illegal among most European nations by the early 1800s (the Portuguese in Brazil and the plantation Americans were long-time holdouts, with the Brazilians finally outlawing slavery the year after the American Civil War ended (1866).
The providing of slaves meant something to pay off the traders, which meant textiles, liquor and manufactured goods (including weapons, of course) flowing south from Europe to Africa, slaves from Africa to the Americas and then sugar, tobacco, cotton and whatever other raw materials the Americas could produce flowing back to Europe. For two centuries, this triangle made Europe the richest most powerful political force on earth, not to mention the added impetus for overcoming things like disease, navigation, enemy aliens and other 'problem-solving' methods that were employed in order to keep the guns, liquor, slaves, sugar and tobacco flowing. The pressure to remove obstacles from the paths of the traders - and the competition between mariner states to get a bigger share - built the western pattern of science, medicine, politics and economic drive we have inherited. Of course, we still have these triangles - but they are interwoven triangles and quadrangles that bind the hands of states beholden to rich assholes, enabling the horror show in Zaire, Colombia and Indonesia to go on and on.
Coming back to D&D, faced with a world like this, in the big scale of our world as it was, there's little the players could do. They might seize a backwater for a time, even make it civilized, but the overall buying, trading and misery would simply continue unabated. This is part of the reason why people don't like slavery in their campaigns (though I doubt they've given it this much thought): there's no cure for it, not that a party can bring about. The only real cure was centuries of time and a steady re-evaluation of racism and human value. At any one moment in time, however, the party just feels helpless.
Most don't want that helplessness to invade their 'fantasy' game. I'm different that way. I don't see fantasy as fuzzy bunnies and roses; I see it as a methodical, institutionalized investigation of the human soul, dark sides included. Then, when we step out of the game chamber, we can appreciate the light that is the modern world with context, hope, satisfaction and perhaps a greater resolve.