Immigrants from the West Indies at Victoria Station in London, 1956. (Photo by Hulton-Deutsch Collection/CORBIS/Corbis via Getty Images)

People out in Aberystwyth on “Booze Black Friday” or “Mad Friday” in Aberystwyth, Wales, UK on December 16, 2016. The “Booze Black Friday” is the last working Friday before Christmas when workers celebrate with their colleagues. Alcohol sales in pubs, clubs and off-licences rise dramatically on this day. (Photo by Keith Morris/Alamy Live News)

In this October 15, 2014 file photo, Katsu Nakamura, sky division manager for Yamaha USA, moves the RMax unmanned helicopter into position before a demonstration of its aerial application capabilities at the University of California, Davis' Oakville Station test vineyard in Oakville, Calif. Researchers at UC Davis have been studying the effectiveness of the drone's ability for spraying pest control and nutritional materials on the test vineyard in California's Napa Valley. (Photo by Rich Pedroncelli/AP Photo)

An Indonesian boy waits as he prepares to catch offerings released by Hindu devotees of the Tengger tribe during the Yadnya Kasada festival, on the crater of Mount Bromo in Probolinggo on July 21, 2016. During the annual Yadnya Kasada festival the Tenggerese climb Mount Bromo, an active volcano, and seek the blessing from the main deity Hyang Widi Wasa by presenting offerings of rice, fruit, livestock and other local produce. (Photo by Juni Kriswanto/AFP Photo)

“Don't Leave Any Food On Your Plate”. The giraffes at Nairobi's Giraffe Manor are totally at home with humans. They will eat out of your hand, or even off your plate. Photo location: Giraffe Manor, Nairobi, Kenya. (Photo and caption by Gavin Werbeloff/National Geographic Photo Contest)

Children react as a carnivorous theropod known as the Australovenator dinosaur walks through crowds along the Southbank, in London, Monday, February 18, 2013. The dinosaur is one of many that can be visited at the Erth's Dinosaur Petting Zoo, visiting from Australia, the creatures can be touched and fed at the Southbank Centre. (Photo by Kirsty Wigglesworth/AP Photo)

Smithfield meat porters march on the Home Office, bearing a petition which calls for an end to all immigration into Britain, 25th August 1972. (Photo by Keystone/Hulton Archive/Getty Images)

Heavy artillery on parade during a review of the Moscow Garrison troops during the May Day celebrations in Red Square, passing posters of Lenin and Stalin. (Photo by N. Sitnikov/Hulton Archive/Getty Images). 1st May 1947