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Have any of you guys been to high school? You should know how evolution by natural selection works. Now apply the same logic to memes. Some memes evolve, some memes grow stronger, some memes die out. The strongest and adaptable memes like Pepe and Wojak have lived on because they have proved their flexibility, while the weaker dinosaur memes like Trollface and Rage Comics simply died off. It's common sense really.