The picture that emerges when you look at animals this way is a far cry from the simplistic wind-up-toy model of old—a model that presented animals as virtual automatons, sleepwalking through life. In addition to indications of intelligence, there are strong suggestions of animal capacity for emotions and states of mind that most people would identify as human. And once you begin to see these capacities in animals, it becomes impossible to believe that the natural world is an us-and-them proposition. Humans, it turns out, don't hold the patent on characteristics that "humanity" comprises: humor, generosity, love, even empathy—a trait that, in the animal kingdom, is far rarer than love because it requires the emotionally sophisticated act of understanding another's plight. (I'm thinking of a female chimp at the Dallas Zoo consoling a zookeeper who had lost her daughter. Or Sophi, an elephant at the Indianapolis Zoo, who, after watching a keeper struggle to push a cart up a hill, walked over and began pushing the cart herself.)

Understanding another's plight requires consciousness. In its simplest form, consciousness means that we recognize ourselves as separate from other creatures. It's a tremendously powerful evolutionary development—and it doesn't just lead to empathy. If you are aware of yourself as distinct from others, you can understand that others might know something that you don't. You can also understand that you might know things others don't—which is the basis of trickery and subterfuge, not to mention a good prank.

In children, this awareness doesn't emerge until sometime between 3 and 4 years of age. The old view was that in animals it never emerges, but in that case, how to explain the game witnessed by Suzan Murray, chief veterinarian of the National Zoo, when, as a veterinary student, she was doing research on chimps in Tanzania's Gombe National Park?

In the late afternoon when the young chimps were playing, Murray would sometimes see an adolescent sneak up behind one of the alpha males and proceed to make rude gestures to another adolescent. The offended youth would respond with a threat, and the alpha male, thinking the threat was directed at him—a huge breach of etiquette in chimp-world—would become enraged at the poor dupe. The prank suggests that the chimp was intentionally manipulating the big male.

Like Wall Street types, some animals are savvy enough to game the system. Spock, a dolphin at another now defunct marine park in California, discovered that if he brought stray pieces of paper to his trainer, he would be rewarded with treats. But the trainer, Jim Mullen, wasn't always around when Spock found a piece of paper. Perhaps this is why Spock started hoarding, collecting pieces and wedging them against an outflow pipe, demonstrating an admirable thrift and an understanding of the basic principles of paper money and banking.

Chantek, an orangutan raised in a lab as part of a language experiment at the University of Tennessee at Chattanooga, stumbled upon the concept of inflation during his off hours. Part of his day involved doing simple chores, for which he was paid in poker chips. Eventually he figured that he could extend the supply of chips simply by breaking them in half. When Lyn Miles, the scientist in charge of the experiment, switched to metal washers to thwart the scheme, Chantek moved on to counterfeiting—collecting pieces of aluminum foil and rolling them into crude circles to look like washers. Countless other stories suggest that animals are quick studies when it comes to estimating the value humans put on various objects—itself a sophisticated ability—and are not above cheating when they can get away with it. (Once, when asked to share some grapes with me, Chantek gave me the stem and kept the grapes for himself.)


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