Two guards perform an execution in China, one holding the gun, the other holding a mask over the victim's face. (Photo by General Photographic Agency/Getty Images). Circa 1925

A chimpanzee feeding a leopard cub at Southam Park Zoo, Warwickshire. (Photo by Ian Tyas/Keystone Features/Getty Images). 1971

The world's biggest wild animal farmer, Carr Hartley of Rumuruti in Kenya, sells animals to zoos, circuses and film companies. (Photo by Maxim Ruston/BIPs/Getty Images). November 1956

A rail worker fixing a fog warning notice at South Woodford Railway Station in Essex. (Photo by H. F. Davis/Topical Press Agency/Getty Images). 20th October 1938

A Viet Cong suspect holds his hands up after a Vietnamese Ranger from the 21st Vietnam Infantry Division routed him from his hiding place. (Photo by Keystone/Getty Images). 7th November 1967

Dog puppy “Sandy” protects against the rain with an umbrella fixed on her leash during a stroll in Rust, southern Germany, on May 26, 2013. (Photo by Patrick Seeger/AFP Photo)

A competitor shows her tattoos at the MBK Tattoo Contest in a shopping mall in Bangkok October 23, 2014. (Photo by Athit Perawongmetha/Reuters)

This photo taken November 10, 2015 shows homeless street children sleeping in a park in Manila. The Philippines has swept 20,000 homeless from the streets, cancelled hundreds of flights and declared public holidays in Manila to ensure a safe and efficient summit of 21 world leaders next week, officials say. (Photo by Jay Directo/AFP Photo)