Emily Hasler, an English Heritage employee at Charles Darwin's home, Down House, cleans a rabbit bone in his old study on April 2, 2011 in Downe, England. Staff at the house are cleaning and preparing the property ahead of their peak visitor season. The house contains the study where Darwin wrote “On the Origin of Species”, as well as family rooms and an extensive garden that inspired the renowned scientist. (Photo by Oli Scarff/Getty Images)

A three-week-old chihuahua puppy named Tom Thumb poses in a tea cup on April 7, 2009 in Renton, Scotland. The pup, which measures eight inches long, is thought to be one of the smallest dogs born in the UK and is just two inches short of a world record. (Photo by Jeff J Mitchell/Getty Images)

An orphaned 11 month old cougar cub plays at Six Flags Discovery Kingdom on April 26, 2007 in Vallejo, California. Three cougar cubs were given to the park from the Idaho Fish & Game in March after they were found motherless in the wild and it was determined that they would not survive in the wild. (Photo by David Paul Morris/Getty Images)

These tiny little sugar gliders are lucky to be alive after surviving a cat attack that killed their mother. Somehow the youngsters, who were just a few days old at the time, and the size of jellybeans, survived and were rushed to the Currumbin Wildlife Hospital in Queensland, Australia. (Photo by Adam Head/Newspix/REX Features)

An adorable 11-week old lion cub named Karis had a very exciting day playing in a pile of autumn leaves that her keeper swept into her enclosure at the Blair Drummond Safari and Adventure Park in Scotland. This proved to be a very wise decision on her keeper’s part, as she seems to have had the time of her life frolicking around in the pile of leaves

Russian participants adjust their hair, preparing for the Kremlin Cadet Ball in Moscow, Russia, 08 December 2016. Pupils of cadet schools from different parts in Russia gathered for the first Kremlin Ball, restoring an old tradition of Russian officers and noble girls. (Photo by Sergei Chirikov/EPA)

A boy looks inside the skull of a Tyrannosaurus Rex replica at the Egidio Feruglio Museum in Trelew, Argentina, in this May 18, 2014 file photograph. Scientists on July 28, 2015 unveiled a comprehensive analysis of the teeth of the group of carnivorous dinosaurs called theropods, which include the Tyrannosaurus Rex, detailing a unique serrated structure that let them chomp efficiently through the flesh and bones of large prey. (Photo by Maxi Jonas/Reuters)

In this November 18, 2014 photo, Murshida, 12, sits on the lap of her mother Marjina as the train leaves for their village in West Bengal, at a railway station in New Delhi, India. Six months ago, Marjina stepped off a train in New Delhi with her two children, hoping to find a better life after her husband abandoned them without so much as a goodbye. The family spent their days at a landfill picking through other people’s garbage to find salvageable bits to resell or recycle. After six months of poverty, illness and shame, they returned to that train station in New Delhi, headed back to an uncertain future to their hometown in West Bengal. (Photo by Altaf Qadri/AP Photo)