Armed Karo herdsman just back from protecting their cattle herds come down to the river to wash decorative clay markings off their bodies at the end of the day in the Omo Valley, South West Ethiopia. Dus, Omo Valley, Ethiopia, January 2008. (Photo by Brent Stirton/Discovery Communications)

Vehicles and weapons of the Justice and Equality Movement (JEM) rebels are seen on display, after victory celebrations by the Sudanese Armed Forces (SAF) and the Rapid Support Forces (RSF), in Niyala Capital of South Darfur, May 4, 2015. (Photo by Reuters/Stringer)

A supporter of “Si” vote cries after the nation voted “NO” in a referendum on a peace deal between the government and Revolutionary Armed Forces of Colombia (FARC) rebels, at Bolivar Square in Bogota, Colombia, October 2, 2016. (Photo by John Vizcaino/Reuters)

Members of the Honour Guard and the central military band of the Mongolian armed forces perform during the International Military Music Festival “Spasskaya Tower” media preview in Red Square in Moscow, Russia, August 26, 2016. (Photo by Sergei Karpukhin/Reuters)

A young arab boy, armed with a rifle and a knife, in the Aden Protectorate near Yemen. (Photo by Richards/Fox Photos/Getty Images). February 1938

A model poses with her arm after it was painted by body artist Guido Daniele into the likeness of a snake at Harrods on Februrary 4, 2008 in London, England. Guido Daniele has painted human hands since 2000. Each work of art takes over three hours to complete. (Photo by Chris Jackson/Getty Images)

A demonstrator wears a message on a t-shirt in Tahrir Square on May 27, 2011 in Cairo, Egypt. The ruling Supreme Council of the Armed Forces said that there would be no use of violence against protests dubbed “the Second Revolution of Anger” taking place in Cairo and other cities in Egypt. (Photo by Peter Macdiarmid/Getty Images)

A girl gets her arm sketched with a body paint tattoo depicting the traditional Dandiya dance, ahead of Navratri, a festival when devotees worship the Hindu goddess Durga, in Ahmedabad, India, September 25, 2016. (Photo by Amit Dave/Reuters)