The secretive indri (Indri indri) of Madagascar, the largest living lemur. It is also critically endangered and highly evolutionarily distinct with no close relatives, which makes its branch one of most precarious on the mammal evolutionary tree. In the likely event that the indri goes extinct, we will lose 19m years of unique evolutionary history from the mammal tree of life. (Photo by Pierre-Yves Babelon/Aarhus University)

A Polisario fighter sits on a rock at a forward base on the outskirts of Tifariti, Western Sahara, September 9, 2016. At a rocky outpost in Western Sahara, a new generation of soldiers who have never known war are mobilising as tensions resurface in one of Africa's oldest disputes after a quarter century of uneasy peace. (Photo by Zohra Bensemra/Reuters)

In this photo taken Friday, September 4, 2015, tourists Sarah and John Scott from Worcester, England, take a step back as a male silverback mountain gorilla from the family of mountain gorillas named Amahoro, which means “peace” in the Rwandan language, unexpectedly steps out from the bush to cross their path in the dense forest on the slopes of Mount Bisoke volcano in Volcanoes National Park, northern Rwanda. Deep in Rwanda's steep-sloped forest, increasing numbers of tourists are heading to see the mountain gorillas, a subspecies whose total population is an estimated 900 and who also live in neighboring Uganda and Congo, fueling an industry seen as key to the welfare of the critically endangered species as well as Rwanda's economy. (Photo by Ben Curtis/AP Photo)

The CBRE Urban Photographer of the Year competition – now in its ninth year – encourages professional and amateur photographers to capture cities at work. Here: Dog Walker – 15:00. The competition allows photographers to enter up to 24 images, one representing each hour of the day. (Photo by Johanna Siegmann)

In this June 20, 2014, file photo, lobsters are processed at the Sea Hag Seafood plant in St. George, Maine. More and more American and Canadian-caught lobsters have been turning up at fancy restaurants in China, marketed as “Boston lobster”, say Maine-based processors. One processing firm owner says it's now the biggest live lobster important day of the year after Christmas in Europe. (Photo by Robert F. Bukaty/AP Photo)

These images capture the intricate details of minuscule snowflakes, moments before they melt. The shots were taken by Don Komarechka, 31, who has had a lifelong fascination with all things macro – especially snowflakes. The professional photographer says people often don’t believe that his pictures are real because they’re so perfect. (Photo by Don Komarechka/Caters News Agency)

Born with a rare condition, the artist has chronicled her life in portraits – capturing everything from her tattooed prosthetics to the tentacled creature she stitched together on the shores of Naoshima. Here: Ophelia (2013). From a series of photos of imagined women exhibited at the 2013 Aichi Triennale. Here, Katayama invokes Hamlet’s tragic heroine, after the painting by British pre-Raphaelite John Everett Millais. (Photo by Mari Katayama/The Guardian)

A stewardess holding a lightsabre poses for photos with visitors during a tour of the Star Wars themed All Nippon Airways ANA R2D2 Boeing 787 Dreamliner aircraft at Singapore's Changi Airport November 12, 2015. The aircraft was opened to the media on Thursday as it makes its first Asian stop outside Japan. (Photo by Edgar Su/Reuters)