Two robotic legged squad support system (LS3) machines by the Defense Advanced Research Project Agency follow a technician during a demonstration at Joint Base Myer-Henderson Hall, Virginia, on September 10, 2012. (U.S. Marine Corps photo by Sgt. Mallory S. VanderSchans via The Atlantic)

People take part in the Classic Ride Rally in downtown Valencia, eastern Spain, 23 November 2014. Some hundred people on classic bikes from the 20's to the 70's participated in the rally. (Photo by Kai Foersterling/EPA)

Inmates ride in a bus out of the Cojutepeque prison in El Salvador, Thursday, June 16, 2016. This prison, which houses more than a thousand 18th street imprisoned gang members, will be closed down by the government, since it has been unable to prevent the amount of illegal activities happening inside the prison walls. Inmates will be relocated to other medium-security prisons. (Photo by Salvador Melendez/AP Photo)

A Pakistani farmer guides his bulls as he competes in a traditional bull race in Khunda village in the northwestern district of Attock, some 80 kilometers from Islamabad on January 3, 2015. Tens of thousands of people gather whenever there is a bull race held in Pakistan which are usually the highlight of festivals organized in rural areas of the Asian country, and attract lots of spectators due to their thrilling nature. The traditional competition attracts landlords and farmers from all around the province where the race is held, and they all bring their fastest and strongest bulls in hopes of gaining a reputation. (Photo by Aamir Qureshi/AFP Photo)

Paramilitary policemen carry tyres as they take part in a training session in Zhangye, Gansu Province, China, March 1, 2016. (Photo by Reuters/Stringer)

China Airlines stewardess Wang Wen Hwang leaps from the burning China Airlines plane after assisting the passengers to safety February 27, 1980. Miss Wang saved most of the lives of the passengers despite her injuries. She was the last to leave the planes. (Photo by AP Photo)

This picture taken on November 1, 2014 shows Japanese body-painting artist Hikaru Cho (L) adding the finishing touches to a body painting of fingers sticking out from prison cell bars on the head of Ryonosuke Tanaka during “Tokyo Designers Week” in Tokyo. Cho, 21, was born to Chinese parents in Japan and burst onto Tokyo's art scene when she entered the city's Musashino Art University in 2012. Cho's ultimate ambition is to paint an entire – and naked – body. (Photo by Yoshikazu Tsuno/AFP Photo)

Armed forces veteran Frank Simpson at the Portico library being camouflaged by body artist Carolyn Roper in Manchester, UK on May 16, 2016 as part of the #CountThemIn campaign launched on Monday by the Royal British Legion. (Photo by Jon Super/Royal British Legion/PA Wire)