From the sirens of “The Odyssey” to “The Creature From the Black Lagoon” and beyond, humans have always imagined their underwater doubles. In this two-part Stuff to Blow Your Mind exploration, Robert Lamb and Joe McCormick discuss the revealing myth and fiction of mermaids and gillmen -- as well as the aquatic ape theory and the biological possibilities of an aquatic humanoid. (Originally published Jan. 23, 2018)

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