Young man making the O.K. sign. (Photo by George Marks/Retrofile/Getty Images). Circa 1950s

Young female Ibex on the fork of Disteis (2,200 m), near the top of the Jof di Montasio (Friuli, Italy). (Photo by Stefano Zocca)

Members of the Mayossa Folk Dance Group pour water on young women in Kiskunmajsa, some 140 kms southeast of Budapest, Hungary, Monday, April 2, 2018. According to a several hundred years old tradition of Hungarian villages young men pour water on young women who in exchange present their sprinklers with beautifully colored eggs on Easter Monday. (Photo by Sandor Ujvari/MTI via AP Photo)

A traditional game that earned hollers from the crowd saw a male rider gallop after a young woman, stretching for a kiss. Only a handful of the men managed the risky peck before the young women turned the tables and thundered after the men with whips in hand. (Photo by Amos Chapple/Radio Free Europe/Radio Liberty)

It’s enough to make your head spin. The photographer Katherine Young set out to shoot spiral staircases in London, England to great effect, including this shot she calls the Downward Spiral Part III. (Photo by Katherine Young/Rex Features/Shutterstock)

Pokot men carry a part of a carcass of a bull killed by a young man during an initiation ceremony in Baringo County, Kenya, January 20, 2016. Far from the bustling city of Nairobi, in an isolated corner of Kenya's Rift Valley, young men from the Pokot community spear a bull in a ceremony called Sapana that takes them into adulthood. (Photo by Siegfried Modola/Reuters)

Juno, a Beluga whale, greets a young viewer at the Mystic aquarium in Connecticut, USA on December 5, 2015. (Photo by Tim Clayton/Corbis)

Young U.S. visitors pose for a photograph next to a vintage car in Havana March 16, 2016. (Photo by Ueslei Marcelino/Reuters)