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 sandstorm hits the city of Zhangye in Gansu province, China on November 27, 2018. (Photo by Reuters/China Stringer Network)

Tourists take photos from a panoramic viewing deck on Victoria Peak in Hong Kong, China, 26 January 2019. Hong Kong has been ranked the world's freest economy by the Heritage Foundation, a conservative research and educational institution based in Washington, for the 25th consecutive year, but the researchers also said the judiciary had become less effective. (Photo by Jerome Favre/EPA/EFE)

A pedestrian carries an umbrella as they stroll past an advertisment as a rainstorm moves through Sacramento, Calif., Wednesday, February 13, 2019. Rain is falling widely in Northern California and is expected to spread south. (Photo by Rich Pedroncelli/AP Photo)

Shaymaa Ismaa’eel, a 24-year-old Muslim woman passes by a group of angry protesters at an Islamic conference in Washington, DC on April 21, 2019. In response, she crouched in front of them and flashed a peace sign. The photo, posted on Instagram, prompted an outpouring of support. (Photo by Shaymaa Ismaa'eel/Instagram)

Revelers pose before the start of the Los Angeles Pride parade on June 9, 2019 in West Hollywood, California. The 49th annual parade, celebrating LGBTQ identity, drew thousands to the streets of West Hollywood. (Photo by Mario Tama/Getty Images)

Demonstrators protest against bullfighting in front of the City Hall a day before of the famous San Fermin festival, in Pamplona, northern Spain, Friday, July 5, 2019. The festival will begin on July 6 with the “txupinazo” opening ceremony, with people participating in bull runs, music and dance, through the old city. (Photo by Alvaro Barrientos/AP Photo)

Parade goers during Brighton Pride Parade on August 03, 2019 in Brighton, England. Tens of thousands of revellers dressed in rainbow colours and elaborate costumes and descended on the seaside city to ask for equality for all. (Photo by Tristan Fewings/Getty Images)