A tribal Fulani man milks a cow at a local milk collecting centre in Dangwala Karfi village on the outskirts of Nigeria's northern city of Kano January 19, 2016. (Photo by Akintunde Akinleye/Reuters)

A tribal fighter loyal to Yemen's government stands in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)

A bride looks on as she and others wait to take their wedding vows during a tribal mass marriage ceremony, in which 1101 couples took part, on the outskirts of Mumbai, India, February 17, 2019. (Photo by Francis Mascarenhas/Reuters)

An Indian worker paints the hand of a huge clay model of a tribal woman on the Indian state of Karnataka's tableau for Republic Day parade, in New Delhi, India, Friday, January 22, 2016. Security has been tightened around the Indian capital as well as across the country ahead of Republic Day celebrations, held each year on Jan. 26. (Photo by Manish Swarup/AP Photo)

A spiritual leader (R) of the Huni Kui Indian tribe blows an herbal powder into the nose of a tribal member during a ceremony outside the village of Novo Segredo along the Envira river of Brazil's northwestern Acre state, March 9, 2014. Many indigenous groups, including the Huni Kui, Ashaninka, and Madija, live in villages in the Brazilian rainforest near the border with Peru. (Photo by Lunae Parracho/Reuters)

Reuters photographer Siegfried Modola gained access to a circumcision ceremony in rural Kenya for young girls of the Pokot tribe, in Baringo County. Here: a Pokot girl, covered in animal skins, walks to a place where she will rest after being circumcised in a tribal ritual in a village about 80 kilometres from the town of Marigat in Baringo County, October 16, 2014. (Photo by Siegfried Modola/Reuters)