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 stroller walks his dogs in an autumnally colored forest in Cuxhaven, nothern Germany on November 7, 2018. (Photo by Patrik Stollarz/AFP Photo)

Participants pose for photographs as they take part in a “Hat Walk” during London Hat Week in London, Britain on April 7, 2019. (Photo by Simon Dawson/Reuters)

In this photo taken on Saturday, March 9, 2019, a visitor dances in front of a sculpture burning at the Maslenitsa (Shrovetide) festival at the Nikola-Lenivets art park in Nikola-Lenivets village, about 200 kilometers (125 miles) south-west of Moscow, Russia. As part of the celebrations of Maslenitsa (Shrovetide) Holiday in Russian, a folk holiday which heralds the beginning of spring, contemporary artist and park founder Nikolay Polissky built a giant sculpture made of wood and hay which was burnt to ashes during a traditional bonfire. (Photo by Alexander Zemlianichenko Jr./AP Photo)

A home-made steam train, designed by Pavel Chilin, rides on a make-shift railway across country house neighborhood in the settlement of Ulyanovka in Leningrad region, Russia on November 4, 2019. (Photo by Anton Vaganov/Reuters)

Members of the San Francisco Gay Freedom Day Marching Band and Twirling Corps do their thing down San Francisco's Market Street, June 27, 1982. Police estimate the crowd to be 300,000 for the Lesbian/Gay Freedom Day parade and rally. (Photo by Carl Viti/AP Photo)

Family members of a taxi driver offer prayer in front of their taxi during the Vishwakarma Puja or the festival of the Hindu deity of architecture and machinery in Kolkata, India, September 17, 2017. (Photo by Rupak De Chowdhuri/Reuters)

Palestinian man Mohammed al-Hoor, 23, demonstrates his street workout skills in Nuseirat refugee camp, in the central Gaza Strip on May 2, 2017. (Photo by Mohammed Salem/Reuters)