National Geographic : 2016 Nov
the power of eight 71 At the same time, octopuses are as alien as any extraterrestrial you might dream up. For starters, they have three hearts and blue blood. When feeling under threat, they squirt a cloud of ink and jet off in another direction. They have no bones. The only hard parts of their bodies are a parrot-like beak and a nub of cartilage around their brain. This makes it easy for them to vanish through tiny cracks—an ability that allows them to escape, Houdini-like, from all but the most octopus-proofed aquarium. Not only can all of their suckers be moved independently; each one is covered with taste receptors—imagine your body covered with hundreds of tongues. Their skin is embedded with cells that sense light. Most otherworldly of all—but let’s wait on that. First, let’s meet another octopus. You’re standing in a small, windowless office in the Natural History Museum in London. In front of you, on a desk crowded with files, lies a slab of pale, fine-grained stone. Beside you, Jakob Vinther, a burly Dane with blond hair and a ginger beard, is pointing at it. “That thing there is the ink sac,” says Vinther, an expert on fossil invertebrates at the University of Bristol, in Great Britain. “ That’s actually pigment—chemically preserved melanin.” You lean forward to look. The stone is clearly marked with the impression of an octopus. It’s not large: In life the animal would have been perhaps 10 inches long. You can trace the mantle—the baglike structure that housed its gills, hearts, and other vital organs. Ah yes. That dark stain in the mid- dle there—that’s the ink sac. The arms hang down, loosely grouped together, each marked with rows of circles. “And those little round structures,” says Vinther, “those are the suckers.” Octopus fossils are rare; animals with soft bodies generally leave no trace. This fossil is about 90 million years old, which makes it one of the oldest known octopuses. When this animal lived, the extinction of the dinosaurs was still 25 million years in the future. “It comes from a locality in Lebanon where you find all kinds of wonderfully preserved soft-bodied crea- tures,” Vinther says. Lampreys. Fire worms. All entombed, long ago, in fine, chalky mud on the floor of a long-vanished sea. Just as humans are mammals, octopuses are cephalopods. The word is Greek for “head-foot” and refers to their weird anatomy, by which their arms are attached directly to one side of their head while their “torso”—the baglike mantle—is on the other. Cephalopods, in turn, are a type of mollusk—a group that includes snails and slugs as well as clams and oysters. Cephalopods were among the first predatory animals to hunt in the an- cient seas. They evolved more than 500 million years ago—long before fish got going—from a small animal with a shell like a witch’s hat. Indeed, if you were to travel back in time 450 million years, some of the fiercest predators in the oceans would have been shell-wearing cephalopods. Some of these were apparently enormous: The shell of the long-extinct Endoceras giganteum may have been more than 18 feet long. Today there are more than 750 known living species of cephalopods. Besides Of all the animals that lack a backbone, octopuses are the ones that seem the most like us. In part, it’s the way they return your gaze, as if they’re scrutinizing you.