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)

Yang Juan, an employee at Goopal Group, takes a nap in her seat after lunch, in Beijing, China, April 21, 2016. Office workers sleeping on the job is a common sight in China, where a surplus of cheap labour can lead to downtime at work. But in China's technology sector, where business is growing faster than many start-up firms can hire new staff, workers burn the midnight oil to meet deadlines and compete with their rivals. Some companies provide sleeping areas and beds for workers to rest during late nights. (Photo by Jason Lee/Reuters)

A woman shields her face from the sun as she rides her scooter in Ahmedabad, India May 20, 2016. (Photo by Amit Dave/Reuters)

An aspiring Catholic priest Jose Luis Guerra, a member of Raza Nueva in Christ, a project of the archdiocese of Monterrey, and other missionaries hand out a Bible to Angel Castillo, who wants to become a missionary with Raza Nueva, in the municipality of Garcia, outskirts of Monterrey, Mexico, July 12, 2016. In the troubled fringes of the northern Mexican city of Monterrey, an aspiring priest is using his faith to reach out to young gang members and at-risk youth, and bring them into his “Gang of Christ”. (Photo by Daniel Becerril/Reuters)

A dog, at the behest of his owner, rides a skatebaord on April 3, 2017 in Berlin, Germany. The dog's owner, who looked like he might be homeless, coaxed the dog to ride the skatebaord and asked passersby who stopped to watch for money. (Photo by Sean Gallup/Getty Images)

An Indian street vendor selling bananas naps on his fruit cart at the roadside in New Delhi on June 3, 2015. (Photo by Money Sharma/AFP Photo)

Julya Baer, 30, attends a candlelight vigil and celebration of Prince's life in Leimert Park in memory of musician Prince on April 21, 2016, in Los Angeles, California. Prince died earlier today at his Paisley Park compound at the age of 57. (Photo by Kevork Djansezian/Getty Images)

Revellers take part in the traditional “Weiberfastnacht” (Women's Carnival) celebration in Mainz, Germany, February 4, 2016. Germany is celebrating its traditional carnival with tight security after assaults on women during New Year's Eve celebrations across the country. (Photo by Kai Pfaffenbach/Reuters)