Dolphins' relentless smiles aren't smiles at all. According to researcher Lori Marino, the animal's jaw structure just happens to make it look that way — but that hasn't stopped humans from associating their apparently tireless grins with joy, healing, and divinity for millennia. Over the past several decades, that association has led people to believe in a supposed therapeutic relief that comes alongside swimming with dolphins, and healing seminars have popped up to capitalize on the notion. The therapies are marketed heavily toward helping autistic children and can cost thousands of dollars for a session. But as it turns out, there's no more benefit to swimming with dolphins than to running around with a dog.

Over at Aeon Magazine, Marino details the history of dolphins in mythology, early research into the animals' intelligence and healing abilities, and how dolphins may be worse off after a therapy session than the parents of an autistic child who are out a few thousand dollars.