50-year-old Abdul Sumud Shaibu shows a picture of his grandfather on his smartphone. "Look at his height," he says. "My ancestors were giants. Strong and well built." Some of his ancestors even fought against slave hunters, Shaibu says. Sometimes they won but not every time. Losing meant a lifetime of slavery.

Slave trade in West Africa flourished long before the first slaves were sold to the United States of America. By the end of the 15th century, Portuguese ships were bringing African slaves to the country. Occupied by the Europeans in the following decades and centuries, the African west coast turned into a hub for slave export.

The system was called triangular trade because major European powers brought goods such as weapons, textiles or alcohol to the West African coast, to be traded for slaves. From Africa the ships would sail to America, where the slaves were exchanged for coveted raw materials such as tea, coffee or cotton. These goods were then shipped back to Europe.

The living conditions during the journey across the Atlantic, the so-called Middle Passage, were inhumane. All the space available on the slave ships was used down to the last centimeter. The slaves were literally stacked on top of each other. They were chained and did not get enough food or water. Sick slaves were simply thrown overboard to keep infections from spreading.

In the "New World" the slaves were forced to work on cotton and sugar cane plantations. While the owners of the plantations were wealthy, the slaves remained poor. Living conditions for these slaves were harsh. Others worked in the cities as longshoremen or in the household of their owners. Many were used by the mining industry. Punishments and abuse were prevalent.

For many slaves violence was a part of their everyday life. They were whipped, had to wear shackles and were marked with branding irons. Their so-called "owner" could decide whether they were allowed to enter into a relationship. Slaves had no rights and could only hope to be released at some point. These shackles are exhibited today in a museum in the Ivory Coast.

The transatlantic slave trade reached its peak in the 18th century. West Africans accounted for about two thirds of African slaves brought to America. This map shows the coastal ports from which the ships set sail. It is not known how many Africans exactly were enslaved. Estimates point to 40 million people.

The Elector of Brandenburg, Friedrich Wilhelm, had the "Groß Friedrichsburg" colony built on today's Ghanaian coast. Ghana was called "Gold Coast" at the time of the slave trade. From there the Brandenburgers took part in the triangular trade, shipping about 30,000 slaves from 1685 on to the so-called "New World".

In Adidwan, a village in Ghana's Ashanti region, Nana Assenso visits the grave of his great-uncle Kwame Badu. His relative was named in memory of an ancestor who long ago was sold as a slave. Since then, the name has been passed on through the generations in the family. Nana Assenso's son is also called Kwame Badu.

An installation by Ghanaian artist Kwame Akoto Bamfo in the village of Nuhalenya Ada commemorates the enslaved ancestors. Although the British banned the slave trade in 1808 and this ban was confirmed by the Congress of Vienna in 1815, slavery wasn’t really abolished until around 1870. Today, the ruins of the former slave fortresses on Ghana's coast are a reminder of this era.