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Recognizing Ourselves

Based on looks alone, the similarities between humans and some other primates are striking. Many apes and monkeys have humanoid features like intelligent eyes and high foreheads; all possess opposable thumbs that allow them to grasp objects the same way that we do. But as you can see in the NATURE program MONKEY IN THE MIRROR, this resemblance goes far beyond the physical; many things about these primates remind us of ourselves.

Monkey

Apes and monkeys are very similar to humans.

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As infants, humans and chimpanzees have nearly identical skills and habits. Both babies grab at objects, smile at friendly faces, and scream out their frustration when unhappy. For about a year, humans and chimps develop along a strikingly similar line: for instance, a baby chimpanzee can complete puzzles designed for a human of the same age. This similarity begins to disappear around the age of one year, when a chimpanzee's learning curve levels just as a human's is taking off.

A newborn chimp is very much like a human baby.

Great apes, including chimpanzees, gorillas, and orangutans, are the most intelligent other primates. Their complex family structures and social hierarchies resemble our own; they even engage in political struggles over popularity and dominance. Chimpanzees and orangutans have developed tool use: for instance, some chimps use a thin stick to reach inside a termite mound, a thicker stick to probe trees for honey. While these twigs may just look like scraps of wood to us, they are specialized tools meant for specific jobs.

Another test to gauge intelligence is the ability to understand the concept of a mirror. When placed in front of a mirror, most monkeys believe their reflections to be other monkeys. Clearly upset by the intrusion into their personal space, they become aggressive, shouting at the intruder and making threatening gestures. The more advanced great ape involved in this experiment on NATURE reacts in just this way -- at first.

Chimp looking in mirror

A chimpanzee examines her image in a mirror.

After a few minutes, however, the chimpanzee realizes that she is looking at herself. Much like a human youngster who has just discovered the mirror, the chimp begins a thorough examination of her body, using the reflection in front of her as a guide. The ability to tell the difference between another and a reflection of oneself is an important developmental milestone in humans, and another trait that links us closely to our primate cousins.

At Georgia State University, exciting research into the cognitive abilities of other primates is going on. Featured in MONKEY IN THE MIRROR, Kanzi, a bonobo chimpanzee, is slowly but surely learning the English language.

Chimp in lab learning English

Kanzi learns English in a lab.

Kanzi, who has absorbed English lessons since infancy, can point to symbols representing English words; he also seems to understand complex verbal instructions. Not only can he follow familiar directions, he can grasp the meaning of words when they are placed in different contexts. Combinations of words that he has never heard before, such as "Put some soap on the ball," or "Take the vacuum cleaner outdoors," make perfect sense to him, just as they would to a human.

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