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I think some Europeans gave Africa the name of the "Dark Continent" in spite of the great culture that existed in West Africa because it was the first or main thing they saw when arrived in that region of Africa. What this teaches us about judging cultures which we do not know much about is that many times, people have stereotypes and prejudices that are not good because these gave the wrong ideas or impressions about other people, countries, or cultures.
And that is what European superpowers did when arriving at the African continent. They also thought that Africans were "savages" because of the way they lived. They were considered primitive people that needed to be modernized.
But what the Europeans never thought was that African people lived happily with their culture, customs, traditions, and history. And no one gave the Europeans the right to conquer them and colonized them.