When biologist Roland Anderson of the Seattle Aquarium pulled back the tank's lid, I wasn't sure whether it was to let me get a look at Steve or to let Steve get a look at me. Clearly, Steve was looking—his big hooded eye followed me, and a single five-foot-long arm reached out to the hand I held above the water's surface. The arm inched up past my wrist to my shoulder, its suckers momentarily attaching and releasing like cold kisses. I couldn't help feeling as if I was being tasted, and I was, by tens of thousands of chemoreceptors. And I couldn't help feeling as if I were being studied, that a measuring intelligence lay behind that intent eye and exploring arm.
Finally, when the arm's fingerlike tip reached my neck, it shot back like a snapped rubber band. Steve curled into a tight, defensive ball in the corner of the tank. His skin texture changed from glassy smooth to a fissured moonscape; his color changed from mottled brown to livid red—which seemed to signal anger—and he squinted at me. Had something alarmed or offended him? Perhaps we were both a great mystery to each other.
Octopuses and their cephalopod cousins the cuttlefish and the squid are evolutionary oxymorons: big-brained invertebrates that display many cognitive, behavioral, and affective traits once considered exclusive to the higher vertebrates. They challenge the deep-seated notion that intelligence advanced from fish and amphibians to reptiles, birds, mammals, early primates, and finally humans. These are mollusks, after all—cousins to brainless clams and oysters, passive filter feeders that get along just fine, thank you, with a few ganglia for central nervous systems. Genetic studies show that mollusk ancestors split from the vertebrates around 1.2 billion years ago, making humans at least as closely related to shrimps, starfish, and earthworms as to octopuses. And so questions loom: How could asocial invertebrates with short life spans develop signs of intelligence? And why?
Although biologists are just beginning to probe these questions, those who observe the creatures in their natural haunts have long extolled their intelligence. "Mischief and craft are plainly seen to be the characteristics of this creature," the Roman natural historian Claudius Aelianus wrote at the turn of the third century A.D. Today's divers marvel at the elaborate trails the eight-leggers follow along the seafloor, and at their irrepressible curiosity: Instead of fleeing, some octopuses examine divers the way Steve checked me out, tugging at their masks and air regulators. Researchers and aquarium attendants tell tales of octopuses that have tormented and outwitted them. Some captive octopuses lie in ambush and spit in their keepers' faces. Others dismantle pumps and block drains, causing costly floods, or flex their arms in order to pop locked lids. Some have been caught sneaking from their tanks at night into other exhibits, gobbling up fish, then sneaking back to their tanks, damp trails along walls and floors giving them away.
