A heat-stressed koala waits as a resident pours water on its back on December 19, 2015 in Adelaide, Australia. Adelaide is experiencing an extreme heatwave, with temperatures reaching over 40 degrees for five consecutive days. (Photo by Morne de Klerk/Getty Images)

This undated photo provided by the U.S. Fish and Wildlife Service shows two island foxes in Channel Islands National Park, Calif. Three fox subspecies native to California's Channel Islands were removed from the list of endangered species Thursday, August 11, 2016, in what federal officials have called the fastest recovery of any mammal listed under the Endangered Species Act. (Photo by Chuck Graham/U.S. Fish and Wildlife Service via AP Photo)

“Strike Through The Mothership”. Every May for the last 3 years I have driven down to Tornado Alley to capture some amazing storms. This supercell held so much promise to drop a tornado but one small shift in the atmosphere and all that it produced was an extreme lightning show. Photo location: Broken Bow, Nebraska. (Photo and caption by Vanessa Neufeld/National Geographic Photo Contest)

A participant poses with his laptop during the 33rd Chaos Communication Congress on its opening day on December 27, 2016 in Hamburg, Germany. The annual event is bringing together 12,000 computer hackers and activists who will meet over the next four days to share expertise and discuss topics related to the society and the digital world. (Photo by Morris MacMatzen/Getty Images)

Glamorous strongwoman Joan Rhodes exercises her strength whilst tackling housework in her flat in Hampstead, north London, March 1958. (Photo by Ken Harding/BIPs). P.S. All pictures are presented in high resolution.

Back in England, one of the British soldiers that continue to return in their thousands from Northern France, belies any mood of defeat with some high spirited piping on a train. (Photo by Parker/Fox Photos/Getty Images). 1st June 1940

A close up of a caracal lynx's face looking into a camera on January 2014 in Western Cape, South Africa. (Photo by Dale Morris/Barcroft Media)

Jimmy Arnold, an overweight boy from Rochester, bites into a cake. (Photo by Reg Birkett/Keystone/Getty Images). 14th April 1951