Pro-Russian rebels stand near a monument during a ceremony to honour the World War Two defenders of Donetsk from Nazi forces, in Donetsk, in this September 8, 2014 file photo. (Photo by Marko Djurica/Reuters)

In this Friday, August 9, 2019, file photo, Pakistan Rangers soldiers face Indian Border Security Force soldiers at a daily closing ceremony on the Indian side of the Attari-Wagah border. India's recent clampdown has a long history in Kashmir and the conflict has existed since the late 1940s, when India and Pakistan won independence from the British empire and began fighting over rival claims to the Muslim-majority territory. India and Pakistan have fought two of their three subsequent wars over Kashmir, and each administers a portion of the region. India has long seen the Kashmiri struggle for self-determination as Islamabad's proxy war against New Delhi. (Photo by Prabhjot Gill/AP Photo/File)

In this September 10, 1977, file photo, from left, Hua Guofeng, Chinese Communist Party (CCP) chairman and Mao Zedong's immediate successor; Ye Jianying, CCP vice chairman and future ceremonial head of state; Deng Xiaoping, no formal titles at the time but soon to emerge as paramount leader during the reform era; Li Xiannian, CCP vice chairman and future president; Wang Dongxing, head of the leadership bodyguard unit who helped topple the Gang of Four, view the body of later Chinese leader Mao Zedong in Beijing. (Photo via AP Photo)

A migrant labourer brushes his teeth in front of a scrapped helicopter model in Mumbai, India, April 13, 2016. (Photo by Danish Siddiqui/Reuters)

With the help of some fake teeth and multiple exposures, New York AP photographer Eddie Adams' daughter Susan is transformed into a little ghoul on Halloween night, October 31, 1966. (Photo by Eddie Adams/AP Photo)

Imagine living in the sea where it is permanently dark, cold, and food is hard to find. For many animals at depth, it may be weeks to months between meals. If you find something to eat, you have to hang on to it. This is why so many deep-sea fishes have lots of big teeth. This dragonfish, spotted off the coast of Australia, even has teeth on its tongue. They would be terrifying animals ... if they weren’t the size of a banana. (Photo by Julian Finn/Museum Victoria)

“Sperm whale opening it's huge mouth, Ogasawara Islands, Japan. Sperm whales are the biggest carnivorous animals on the planet. Each teeth in the mouth of adult specimen weights more than 1 kilogram. Interestingly enough that modern marine biologists believe that these teeth despite being fearsome play little role in capturing and eating giant squid – with their main function being mainly ritual aggression between males!”. (Photo by Alexander Safonov)