A boy carries sugar cane through a farm on the outskirt of Zaria in Nigeria's northern state of Kaduna November 15, 2016. (Photo by Akintunde Akinleye/Reuters)

A Ukrainian serviceman fires a 2S7 Pion self-propelled gun during military exercises near the village of Divychky in Kiev region, Ukraine, October 21, 2016. (Photo by Valentyn Ogirenko/Reuters)

Only 156 people remained in the tribe when Jan visited in Accham District, Nepal, January 2016. Hidden deep in the Himalayan forest is one of the world’s last enduring nomadic tribes who are resisting attempts to move them into permanent settlements. (Photo by Jan Moller Hansen/Barcroft Images)

In this December 19, 2014 photo, a man stands beside his 1957 Chevrolet Bel-Air car in Havana, Cuba. U.S. car sales have been banned in Cuba since 1959. Cubans have been have been forced to patch together Fords, Chevrolets and Chryslers that date back to before Fidel Castro's revolution which can make it appear like the country is stuck in a 1950s time warp. Since the Communist economic system isn't likely to change soon, many of those cars will have to stay on the road for years. (Photo by Desmond Boylan/AP Photo)

Boys play basketball in the facilities of Belarus' Republican Clinic of Speleotherapy within a salt mine, as part of their treatment, near the town of Soligorsk, south of Minsk, February 19, 2015. According to the state clinic, more than 7,000 children and adults seek medical treatment for respiratory illness each year in the subsurface chambers of its facilities, located 420 metres underground between layers of potassium and stone salts in an operational salt mine. (Photo by Vasily Fedosenko/Reuters)

Indonesian tourists take a selfie as Mount Bromo spews volcanic material and ash into the air during an eruption in Probolinggo, East Java, Indonesia, 31 December 2015. Indonesia's Mount Bromo is on the second highest alert level as its activity has increased in the last two months. (Photo by Fully Handoko/EPA)

Kaylee Cantler, 15, of Waynesboro, Pa., applies blush during a natural makeup exercise at a modeling camp at the Courtyard Marriott Hotel in McLean, Va., on Monday, August 17th, 2015. (Photo by Brittany Greeson/The Washington Post)

The six-months-old female koala cub holds on to the back of zoo keeper Lena at the zoo in Duisburg, Germany, 23 October 2015. The yet unnamed baby weighs 580 grams. (Photo by Roland Weihrauch/EPA)