“The Challenge!” Young boy relishes in a game of tug of war before school. Photo location: Lake Titicaca, Peru. (Photo and caption by Paul Heyman/National Geographic Photo Contest)

Models prepare backstage before a presentation as part of Fashion Weekend Plus Size Summer 2015 collection show in Sao Paulo, July 25, 2015. (Photo by Nacho Doce/Reuters)

Models get ready backstage before the presentation of the Etam Live Show Lingerie at the Fashion Week in Paris, France, September 27, 2016. (Photo by Charles Platiau/Reuters)

Runners sleep before competing in the 2016 New York City Marathon in the Manhattan borough of New York City, NY, U.S. November 6, 2016. (Photo by Eduardo Munoz/Reuters)

Beauty contestants prepare backstage before the fashion show of Miss Tiffany's Universe 2016 transvestite contest in Bangkok, Thailand, April 20, 2016. (Photo by Athit Perawongmetha/Reuters)

An army dog stands up as retiring soldiers salute their guard post before retirement in Suqian, Jiangsu province, China on November 29, 2017. (Photo by Reuters/China Stringer Network)

English fashion designer Mary Quant (R) with a group of models at Heathrow Airport, before leaving for a continental fashion tour, 18th March 1968. (Photo by Express/Getty Images)

Snow blows off the Svalbard Global Seed Vault before being inaugurated at sunrise, Tuesday, February 26, 2008. (Photo by John McConnico/AP Photo)