Model Olivia Culpo (L) and host Nick Jonas, after getting slimed, backstage during Nickelodeon's 28th Annual Kids' Choice Awards held at The Forum on March 28, 2015 in Inglewood, California. (Photo by Lester Cohen/KCA2015/WireImage)

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)

A man rides a horse at a playground on a hill in Kabul April 19, 2015. (Photo by Mohammad Ismail/Reuters)

A volcanic eruption at Mount Etna’s Vorgaine crater in Sicily, Italy on December 3, 2015. (Photo by Marco Restivo/Barcroft Media)

A farmer rides a truck in a village near Nong Khai, Thailand, September 16, 2015. (Photo by Jorge Silva/Reuters)

An Iraqi army cadet performs “the leap of faith” from a bridge in Baghdad, September 22, 2015. (Photo by Ahmed Saad/Reuters)

A portrait of Kazakh historical figure Ablai Khan is projected on a building in downtown Astana, Kazakhstan, October 8, 2015. (Photo by Shamil Zhumatov/Reuters)

Students play in their school yard on the first day of the new school term at a primary school in Baghdad, October 18, 2015. (Photo by Ahmed Saad/Reuters)