The skulls of 20 Namibians have been returned to tribal leaders, more than a century after German scientists used them for experiments to try to prove the “racial superiority” of white Europeans over black Africans.

The tribal leaders reclaimed the skulls Friday at a ceremony in Berlin, a reminder of Germany's colonial past in Africa at the turn of the 20th century. German control included the bloody suppression of an ethnic uprising by the Herero and Nama ethnic groups between 1904 and 1908 that left tens of thousands dead.

The heads of four females and 16 males had been removed from their bodies. It was not clear how they died, although possibly they were victims of German forces or died in a German-run camp. Their remains were sent to Berlin.

The head of the Berlin Medical Historical Museum, Thomas Schnalke, said scientists at the time attempted to prove that white Europeans were superior to black Africans through analysis of the facial features of the heads. Later, the skulls sat in German archives until they were discovered three years ago at the museum at Charite University and at Freiburg University.

Charite's board chairman, Karl Max Einhaeupl, said the university deeply regrets “the crimes that were committed back then” and sincerely apologizes for it.

Some of the tribal leaders had hoped the German government would use the occasion to apologize for its colonial occupation, but that did not occur. Germany has refused to pay reparations to its former colony, saying it has given extensive development aid to the South African nation.