What Dolphins Are Thinking

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 ullstein bild / Getty Images


After writing two best-selling aquatic-themed books (The Devil’s Teeth, about great white sharks, and The Wave: In Pursuit of the Rogues, Freaks, and Giants of the Ocean), Susan Casey already had cetaceans on her sonar when she had an encounter with a pod of about 50 spinner dolphins near her home in Maui.

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Swimming alongside them, she found that the creatures’ “otherworldly” demeanor lifted her out of a depressive funk. Casey became obsessed with dolphins, spending two years researching her new book, Voices in the Ocean: A Journey Into the Wild and Haunting World of Dolphins, talking to scientists, visiting marine parks and illegal dolphin-trafficking markets — and even attending dolphin teleportation workshops.

While Casey gives a sympathetic ear to New Age theorizing about dolphins’ supposed supernatural powers, thankfully it’s the scientific evidence she reveals that truly distinguishes Voices in the Ocean. “The thing that struck me the most is this notion of how their brains developed and for how long,” says Casey about the mammal arguably closest to humans in intelligence and whose genome is strikingly similar to our own. Humans have had our large brains for somewhere between 200,000 and 800,000 years; dolphins, however, have had theirs for about 35 million years.

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The neocortex in the dolphin brain (the area in the mammalian brain that allows us to reason, think, and socialize) has one less layer than in humans, so the way information enters and is processed is completely different. They also have an estimated three times more spindle-cell neurons — responsible for functions such as judgment, intuition, and awareness — than humans. And dolphins are one of the very few animals who can recognize themselves in a mirror, though their brain architecture suggests that their idea of self may be different from, and far more communal than, our own.

“There may be a sense where they take sociality to such a level that the group is a kind of a self,” says Casey. “And that just totally blew my mind.”