German researchers believe the skulls belong to 11 people from the Nama ethnic group and nine from the Herero; four women, 15 men and a boy.
The historical background is that in the 1880s, Germany acquired present-day Namibia, calling it German South-West Africa. In 1904 the Herero, the largest of about 200 ethnic groups, rose up against colonial rule killing more than a 120 civilians. In the consequence of the German response 50.000 Herero and about 10,000 Nama people died.
German scientists took the heads to perform experiments seeking to prove the racial superiority of white Europeans over black Africans. Charite spokeswoman Claudia Peter said the purported research on the skulls performed by German scientists had been rooted in perverse racial theories that later planted the seeds for the Nazis' genocidal ideology.
In 1985, a UN report classified the events as an attempt to exterminate the Herero and Nama peoples of South-West Africa, and therefore the earliest attempted genocide in the 20th Century. In 2004, Germany's ambassador to Namibia expressed regret for what happened.