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I'm not sure this question has been posted before, but I didn't see it so here goes.

What person in history (pre-1900) if removed would most likely alter the look of our world today. Again, who if vanished from history would directly or indirectly change the 'shape' or our 21st century the most? Can be technologically, militarily, or philosophically ... anything. Religious leaders from any religion are excluded from the question.

If that's too vague or equivocal then perhaps let me narrow it down. Same question but specific to A.) Europe? B.) Asia? C.) North and South America?
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