Festival goers arrive for the Glastonbury festival at Worthy Farm, in Somerset, England, Thursday, June 23, 2016. (Photo by Guy Bell/Rex Features/Shutterstock)
A fighter of Libyan forces allied with the U.N.-backed government runs for cover during a battle with Islamic State fighters in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)
Participants run through the streets of the Back Bay during the 16th annual Santa Speedo Run in Boston, Massachusetts, December 12, 2015. (Photo by Brian Snyder/Reuters)
A man holds his umbrella during snowfall on the Areopagitou pedestrian street beneath the Acropolis hill during snowfall in Athens, Greece, January 10, 2017. (Photo by Alkis Konstantinidis/Reuters)
The Korowai, also called the Kolufo, are a people of southeastern Papua (i.e., the southeastern part of the western part of New Guinea). They number about 3,000. Until 1970, they were unaware of the existence of any people besides themselves.