One really cool example of both pareidolia and evolution are the Heike crabs in the Japan's Inland Sea.

Since the ancient times, Japanese fishermen have caught these crabs. However, some of them have markings in their backs which resemble a human face. The fishermen believed they were spirits of their ancestors (or ancient warriors, something like that) and let them go. Because they were spared and other crabs weren't, the crabs with faces on their backs became more common.

Such crabs exist only in the Inland Sea of Japan.

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Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman