The tusk of a woolly mammoth that lived some 18,000 years ago, from which researchers sequenced the extinct mammal's entire genome, is seen in northeastern Siberia in this photo from 2015. (Photo by Love Dalen/Handout via Reuters)

An internally displaced Afghan girl plays near their shelter at a refugee camp in Kabul January 13, 2015. (Photo by Omar Sobhani/Reuters)

Jenifer Lopez, 12, watches television at her home in Havana January 9, 2015. (Photo by Alexandre Meneghini/Reuters)

A boy sleeps in a hammock while his mother works at a brick kiln on the outskirts of Yangon February 1, 2015. (Photo by Soe Zeya Tun/Reuters)

Locals re-enact the 1573 medieval battle of “Seljacka Buna” in Donja Stubica February 7, 2015. (Photo by Antonio Bronic/Reuters)

A rickshaw man runs under the blooming cherry blossoms in Tokyo, Sunday, March 29, 2015. (Photo by Shizuo Kambayashi/AP Photo)

A stuntman performs while riding a car inside the “Wall of Death” attraction during a fair in Bhaktapur April 20, 2015. (Photo by Navesh Chitrakar/Reuters)