Silver medalist Vivian Jepkemoi Cheruiyot of Kenya and gold medalist Almaz Ayana (R) of Ethiopia during the medal ceremony for the women's 10000m final of the Rio 2016 Olympic Games Athletics, Track and Field events at the Olympic Stadium in Rio de Janeiro, Brazil, 12 August 2016. (Photo by Sergei Ilnitsky/EPA)

A sun bear reacts to triple-digit temperatures at the Henry Doorly Zoo in Omaha, Nebraska, where the temperature reached 103 degrees Fahrenheit on July 6, 2012. (Photo by Nati Harnik/Associated Press)

In this photo provided by Jean Revillard, Solar Impulse 2, a plane powered by the sun's rays and piloted by Andre Borschberg, approaches Kalaeloa Airport near Honolulu, Friday, July 3, 2015. His 120-hour voyage from Nagoya, Japan broke the record for the world's longest nonstop solo flight, his team said. (Photo by Jean Revillard/Global Newsroom via AP Photo)

A man carries his wife on his back as they make their way with their luggage along a flooded tunnel to catch their train, after heavy rainfall hit Jinhua, Zhejiang province, China, July 21, 2015. (Photo by Reuters/China Daily)

“Show us our butts! Mucawana tribe – Angola. In Soba village, the Muhacaona (Mucawana) tribe, perhaps the best place i have visited. They use cow dung and fat to make this so nice haircut, and love the beads. They asked me to make pictures of their backs... and butts to see on the camera screen if everything was perfect!”. (Photo and comments by Eric Lafforgue)

Participants ride horses, hold spears and wear historic armoured suits of the Middle Ages as they compete during the Saint George international knight tournament in Moscow, Russia, May 3, 2015. (Photo by Maxim Zmeyev/Reuters)

Taiwanese-US artist Chin Chih Yang poses for a photograph with 30,000 aluminum cans after his performance called “Kill Me or Change” in Taipei, Taiwan, 23 April 2016. “Kill Me or Change!” is a performance piece that aims to raise awareness of the benefits of recycling and, encourage people to recycle to conserve resources. (Photo by Ritchie B. Tongo/EPA)

Russians play accordions as they walk near the building of the Federal Security Service (FSB, Soviet KGB successor) in Lubyanskaya Square to mark May Day in Moscow, Russia, Sunday, May 1, 2016. As in Soviet times, about one hundred thousand of cheerful workers paraded across Red Square despite a chilly rain, but instead of red flags with the Communist hammer and sickle, they waved the blue flags of the dominant Kremlin party and the Russian tricolor. (Photo by Alexander Zemlianichenko/AP Photo)