Cephalopods behave in ways that certainly suggest they’re highly intelligent.
ies, and by comparing them, scientists have identified some shared factors. The animals have big brains relative to their body size, they live for a long time, and they can form long-lasting social bonds. Those similarities have led to some promising explanations for how certain animals evolved to be smart.
INTELLIGENCE HYPOTHESES
5. One is known as the ecological intelligence hypothesis. It holds that intelligence evolves as an adaptation for finding food. While some animals have a reliable food supply, others have to cope with unpredictability. Other researchers have argued for what’s known as the social intelligence hypothesis: smarter animals “cooperate and learn from other members of the same species,” Amadio said. 6. Together, these forces appear to have encouraged the development of bigger, more powerful brains. Smart animals also tend to live for a long time, and it’s possible that bigger brains drove the evolution of longevity. It takes years for juveniles to develop these complex organs, during which time they need help from adults to get enough food.
WHAT ABOUT CEPHALOPODS?
7. Cephalopods behave in ways that certainly suggest they’re highly intelligent. An octopus named Inky, for example, made a notorious escape recently from the National Aquarium of New Zealand, exiting his enclosure and slithering into a floor drain and, apparently, out to sea. Cuttlefish can scare off predators by forming eyespots on their bodies in order to look like giant fish. But they only use this trick against predators that rely on vision to find prey. If a predator that depends on smell shows up, the cuttlefish are smart enough just to flee.
8. Another feature that cephalopods share with other smart animals is a relatively big brain. But that’s where the similarities appear to end. Most of the neurons that do the computing, for example, are in the octopus’ arms. Most strikingly, cephalopods die young. Some may live as long as two years, while others only last a few months. Nor do cephalopods form social bonds.
EVOLUTIONARY HISTORY
9. Amodio and his colleagues think the evolutionary history of cephalopods may explain this intelligence paradox. About half a billion years ago, their snaillike ancestors evolved to use their shells as a buoyancy device. They could load chambers in the shell with gas to float up and down in the ocean. About 275 million years ago, the ancestor of today’s cephalopods lost the external shell. It’s not clear why, but it must have been liberating. Now the animals could start exploring places that had been off-limits to their shelled ancestors. Octopuses could slip into rocky crevices, for example, to hunt for prey.
10. On the other hand, losing their shells left cephalopods quite vulnerable to hungry predators. This threat may have driven cephalopods to become masters of disguise and escape. They did so by evolving big brains. Yet intelligence is not the perfect solution for cephalopods, Amodio suggested. Sooner or later, they get eaten. Natural selection has turned them into a paradox: a short-lived, intelligent animal.