Egyptian bootblacks cleaning a European's shoes in Cairo. (Photo by Hulton Archive/Getty Images). Circa 1870

A polar bear fast asleep at London Zoo. (Photo by Fox Photos/Getty Images). 1961

Figure Skating, ISU Grand Prix Rostelecom Cup 2016/2017, Ice Dance Short Dance, Moscow, Russia on November 4, 2016. Kaitlyn Weaver and Andrew Poje of Canada compete. (Photo by Grigory Dukor/Reuters)

American model and television personality Kendall Jenner attends the Tiffany & Co. Paper Flowers event and Believe In Dreams campaign launch on May 3, 2018 in New York City. (Photo by Jamie McCarthy/Getty Images for Tiffany & Co.)

Tarah Kayne and Daniel O'Shea of the U.S. perform during the Pairs short program at the Skate America figure skating competition in Milwaukee, Wisconsin October 23, 2015. Fifty-six Olympic and world championship athletes are competing in the event, which is the first of six stops on the International Skating Union (ISU) Grand Prix of Figure Skating Series. (Photo by Lucy Nicholson/Reuters)

Astrid Perez (L) and Ramon Camacho lay on the Playa during the Burning Man 2015 “Carnival of Mirrors” arts and music festival in the Black Rock Desert of Nevada, September 6, 2015. Sunday marks the last day of the sold-out festival that gathered approximately 70,000 people from all over the world. (Photo by Jim Urquhart/Reuters)

A woman, wearing a traditional Sevillana dress, performs as she asks for alms in downtown Malaga, Spain, April 28, 2016. (Photo by Jon Nazca/Reuters)

An African giant pouched rat sniffs for traces of landmine explosives at APOPO's training facility in Morogoro on June 17, 2016. APOPO trains the rats to detect both tuberculosis and landmines at its facility. Every year landmines kill or maim thousands of people worldwide. The trained rats sniff for explosive and so are able to detect the presence of landmines far faster than conventional methods which involve metal detection. (Photo by Carl De Souza/AFP Photo)