Between the 15th and 19th Centuries, it is estimated that up to 12m Africans were forced onto European slave ships and taken across the Atlantic. Two hundred years after the British parliament voted to abolish the trade, the effects on Africa are still being felt.
Head to a village in northern Ghana or indeed many villages in West Africa and at times you might wonder what century you are in. Even though Ghana has achieved impressive growth rates in recent years, the scene in many rural areas appears to have changed little with grass thatched mud walled huts. There is often no electricity and yes, the water is collected in plastic containers these days but it is still quite an effort to fetch it.
'A very long effect'
The Ghanaian historian and lawyer, Mohamed Shaibu Abdulai, says Africa's loss of millions of the strongest men and women during the slave trade is one reason for this underdevelopment.
"The slave trade actually prevented the coming into being of a farming revolution in Ghana, and likewise an industrial revolution. Because before you can industrialise you need to have stable agricultural production. So slavery has a very long effect."
Some estimate that without slavery the population of Africa would have been double the 25m it had reached by 1850.
"During slavery many of the able-bodied people, between 18 and 40, were taken out so society's ability to reproduce itself economically, socially and culturally was reduced," says Zagba Oyortey a Ghanaian cultural historian.
Gold or slaves?
Another legacy of the trans-Atlantic slave trade was the fuelling of conflicts and long lasting rifts between communities which in some cases remain. The European demand for slaves provided a lucrative business for the African slave raiders in the interior. Many of the slaves were prisoners of war, and enslaving an enemy soon became a motive for going to war.
"European traders found it hard to get slaves during times of peace. However, when there was war, gold was scarce and slaves were widely available," says Doctor Akosua Adoma Perbi, the head of the history department at Ghana's Legon university.
"One traveller wrote in his memoirs that in 1681 he had got only eight slaves after combing the whole of Ghana's coast from west to east. But when he asked why that was, he was told the people were at peace. So warfare was a major source of slaves.
Period of great demand
A trader named Bosman wrote, "Wars make gold scarce but negroes plenty," says Doctor Perbi. Doctor Perbi has written a book on the history of slavery in Ghana which, she says, was affected by the trans-Atlantic slave trade.
"The greater demand for slaves for the external market resulted in an increased tapping of the indigenous sources of slave supply. This period of great demand for slaves also coincided with the introduction of guns and gunpowder into Ghana. Non-stop wars of conquest, expansion, aggression and retaliation became a feature of the Ghanaian experience," she writes.