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June 25, 2007
Marino joins cetacean scientists to set record straight on dolphin intelligence

by carol clark

When a South African neuroscientist published a controversial paper on dolphin brains last year, then capped it by telling the media that the beloved marine mammals are dumber than goldfish, Lori Marino’s inbox was flooded with e-mail.

“Dolphins are hot-button animals and that paper got a lot of press,” she said. “Journalists were calling me from all over asking, ‘What do you think of this?’” Her answer: not much.

“The author disregarded decades of work showing very complex cognitive abilities in dolphins,” said Marino, a senior lecturer in Emory’s Neuroscience and Behavioral Biology Program, who produced the first comprehensive analysis of the evolution of dolphin brain size in 2004.

Paul Manger, of Johannesburg’s University of the Witwatersrand, contended in his 2006 paper that the relatively large brains of dolphins are due to a preponderance of fatty glial cells, which evolved to keep their brain neurons warm in the cold ocean environment. He theorized that the intelligence of cetaceans – including dolphins, whales and porpoises — was largely overrated.

“I was floored that his paper saw the light of day,” said Marino. Her groundbreaking research has shown that dolphins can recognize themselves in mirrors, a feat of intelligence previously believed limited to humans and their closest primate cousins.

Marino and 15 other researchers — an international “who’s who” of leading marine mammal scientists — have banded together to counter Manger’s claims. Marino served as lead author for their paper, titled “Cetaceans Have Complex Brains for Complex Cognition,” which appeared in the May issue of PLoS
Biology, a peer-reviewed journal of the Public Library of Science.

“The paper summarizes everything we know about cetaceans from an evolutionary, neurological, behavioral and social point of view,” Marino said. PLoS Biology is an open-access journal, available via the Web site www.plosbiology.org.

Marino and her fellow researchers are currently working on a more technical, point-by-point scientific rebuttal of Manger’s paper. She expects it to be published by early next year in the Biological Review of the Cambridge Philosophical Society, the same journal that published Manger’s paper.

“We want to be in the record in the literature, to address all of his points and basically correct the inaccuracies,” she said. “Dolphins are smart, complex and sophisticated creatures. I don’t want people to get an impression of them that is based on bad science.”

While dolphins are intelligent, many people “go overboard” in the other direction and project all kinds of mystical qualities onto them, Marino added. “They are mammals that live in a totally different world than we do, so there is a sense of mystery. But dolphins are not from another planet. They have not been shown to have healing abilities and they don’t exist just to help people.”

It is in the best interest of people, and of the animals that they admire, “to stay within the boundaries of what we have evidence for,” Marino said.

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