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)

PH Sport's driver Sebastian Loeb races against an airplane during a performance act at the Peru Dakar Rally in Lima, Peru on January 5, 2019. (Photo by Carlos Jasso/Reuters)

A candle burns during a vigil in Aotea Square to remember victims of the Paris attacks on November 14, 2015 in Auckland, New Zealand. According to reports, over 150 people were killed in a series of bombings and shootings across Paris, including at a soccer game at the Stade de France and a concert at the Bataclan theater. (Photo by Hannah Peters/Getty Images)

Valery Bystritskii, 10, gets a fellow student into a lock at Bunny's Gym in July 2015 in Winchester, Tennessee. (Photo by Mike Saliba/Barcroft USA)

A female rebel in Kabul, Afghanistan, circa 1979. Photo taken at a parade in Kabul in honor of the pro-Communist Saur Revolution. She was from the women’s battalion of the people’s militia (one of the anti-imperial groups that participated in the coup d’etat). (Photo by Viktor Khabarov)

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)

An Iraqi shi'ite muslim girl places a copy of the Koran on her head during the holy month of Ramadan at the Imam Ali Shrine, in the holy city of Najaf, Iraq on May 28, 2019. (Photo by Alaa Al-Marjani/Reuters)

Police officers hold a revolver as they offer prayers to their weapons as part of a ritual at their headquarters on the occasion of Dussehra, or Vijaya Dashami, festival in Ahmedabad, India, October 8, 2019. (Photo by Amit Dave/Reuters)