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A new study indicates that, like humans, great apes go through a nadir of happiness in middle age. Image via Wikimedia Commons/Zyance

Stereotypically, people experiencing a mid-life crisis desperately seek to justify their lives through superficial means, perhaps by buying an expensive sports car or getting into a relationship with a younger romantic partner. Although their behavior looks rather different, a new study says that chimpanzees and orangutans go through a mid-life nadir in overall well-being and happiness that roughly resembles our own.

A team led by psychologist Alexander Weiss of the University of Edinburgh asked zookeepers and researchers around the world to keep track of the well-being of resident chimpanzees and orangutans—508 animals in total. The results of all that record-keeping, published today in the Proceedings of the National Academy of Sciences, show that, like humans, these great apes generally experience a U-shaped pattern of happiness and well-being, starting off with high ratings for happiness as adolescents, declining gradually during middle age (bottoming out in their late 20s or early 30s), and then rising back up again in their elder years.

Although popular conceptions of human mid-life crises focus on material acquisitions, psychologists believe they’re driven by an underlying decline in satisfaction and happiness as we go through middle age, and reflected by increased antidepressant use and suicide risk. In this sense, the primates studied went through a similar pattern:

The chimps and orangutans studied went through a human-like U-shaped pattern for happiness over the course of their lives. Image via PNAS/Weiss et. al.

Of course, unlike with humans, no one can directly ask chimps and orangutans how they are feeling. Instead, the researchers relied upon surveys, filled out by zookeepers and caretakers, that rated the animals’ mood and how much pleasure they took from certain situations. They acknowledge the ratings are necessarily subjective, but they feel that the size of the dataset and consistency in the trends as reported from the different zoos with different animals suggests that the pattern is legitimate.

Weiss’ group originally embarked on the ape study to answer the question of why mid-life dissatisfaction is so common in humans. “We hoped to understand a famous scientific puzzle: why does human happiness follow an approximate U-shape through life?” Weiss said in a statement.

Although many are apt to blame external cultural factors such as disappointing careers or mounting bills as the cause, Weiss felt it was something more fundamental. By showing that a similar pattern exists in other primates, he argues that his team has dispelled the notion that these types of external factors are solely responsible. “We ended up showing that it cannot be because of mortgages, marital breakup, mobile phones or any of the other paraphernalia of modern life,” he said. “Apes also have a pronounced midlife low, and they have none of those.”

Instead of these cultural factors, Weiss suggests that this pattern is rooted in biological or evolutionary factors. It might have been the case, for example, that the human ancestors who had an innate tendency for happiness and satisfaction at the stages of life when they were most vulnerable (youth and old adulthood) might have been less likely to venture into risky and potentially harmful situations in the pursuit of more resources.

It only took five tries, but his version of Hamlet is much better. Image courtesy of Library of Congress.

You’ve probably laughed at a commercial or television show featuring a chimpanzee dressed like a little kid. They’re cute animals, so how could you resist? But a new study in PLoS ONE provides startling evidence that turning chimps into entertainers makes us care less about them as a species.

Researchers at Duke University had human participants watch a series of television ads (for products like tooth paste and soda) in which they included either a commercial for chimp conservation featuring Jane Goodall, a bit of footage of chimpanzees in the wild or a commercial that had a chimp dressed like a human. The participants were then given a questionnaire that asked about the suitability of chimps as pets, their presence in the media and their status in the wild. They were also asked if they would like to purchase a soda or a tube of toothpaste or to donate to the Red Cross or a conservation organization.

People who saw the chimps dressed as humans were more likely to view the animals as being suitable as pets or in entertainment and were the least likely to donate to the conservation organization. The researchers write:

Advertisers only use easily manageable young chimpanzees in commercials but based on our survey viewers believe these chimpanzees were adults—leaving them unaware of how dangerous these animals can be when fully grown. Such a frivolous use of chimpanzees also leads those watching chimpanzee commercials to overestimate their population size in the wild. Clearly, chimpanzee commercials violated participants’ expectations about how perilously endangered animals are treated. This confusion likely explains why those watching commercials including entertainment chimpanzees donated the least of their experimental earnings to a conservation charity.

“Nobody has measured this sort of thing before, but [our study] clearly shows that the portrayal of endangered species on television can alter viewers’ behaviors and decrease one’s willingness to donate,” says graduate student Kara Schroepfer, the study’s lead author. “This is a clear indication that we need to reevaluate media practices and conservation priorities.”

And the impact of using chimps as entertainers goes beyond the money issue. If people think that chimps make good pets—which is seriously misguided—then more young chimpanzees may be captured in the wild, their mothers killed, so they can be sold into the pet trade. And there is a sad history of chimps being abandoned or killed when they get too old and too dangerous to be cute.

Kanzi the bonobo is quite the musician. Image courtesy of the Great Ape Trust

In the new movie Rise of the Planet of the Apes, the leader of the ape revolution can talk. In the real world, apes can’t speak; they have thinner tongues and a higher larynx, or vocal box, than people, making it hard for them to pronounce vowel sounds. But that doesn’t necessarily mean they don’t have the capacity for language—sign language, after all, doesn’t require any vocalization.

Over the years, researchers have succeeded—and failed—in teaching apes to use language. Here’s a look at some of the more famous “talking” apes.

Viki: Viki, a chimpanzee, came closest to being a real talking ape. In the late 1940s and early 1950s, Keith and Catherine Hayes of the Yerkes Laboratories of Primate Biology, then located in Orange Park, Florida, adopted Viki and raised her at home as if she were a human baby. With the Hayeses moving her lips for her, Viki learned to utter “mama.” Eventually, with much difficulty, she managed to say three other words—papa, cup and up—on her own. Viki’s tenure as a talking ape didn’t last long; she died at the age of seven of viral meningitis.

Washoe: In the 1960s, psychologists Allen and Beatrix Gardner of the University of Nevada, Reno recognized that chimpanzees naturally gesture a lot and thought chimps would be well suited for sign language. In 1966, they started working with Washoe. Later, psychologists Roger and Deborah Fouts, now retired from Central Washington University, continued the work. By the end of Washoe’s life in 2007, she knew about 250 signs and could put different signs together to make simple combinations like “Gimmie Sweet” and “You Me Go Out Hurry.” Washoe’s adopted son Loulis also learned to sign—by watching his mother. He was the first ape to learn signs from other apes, not humans. For more on Washoe’s life, read Roger Fouts’ Next of Kin.

Nim: After the success with Washoe, psychologist Herbert Terrace of Columbia University decided to replicate the project. At first, Nim—full name Nim Chimpsky, named after linguist Noam Chomsky who thought language was unique to humans—was raised in a human household. (Washoe had been treated like a person too but had her own trailer.) Later, Nim was removed from the family and his language lessons moved to a lab on Columbia’s campus. In the end, Terrace concluded Nim never really learned language; he had merely been trained to imitate his teachers to get rewards. The sad story of Nim’s life after the project ended is told in the new documentary Project Nim.

Chantek: Chimpanzees are not the only talking apes. In 1978, anthropologist Lyn Miles of the University of Tennessee at Chattanooga began studying an orangutan named Chantek. During eight years of study, Chantek learned 150 signs. He also showed signs of being self-aware: he could recognize himself in a mirror. Today, you can visit Chantek at Zoo Atlanta, his home since 1997.

Koko: Koko the gorilla is probably best known for her love of kittens and Mr. Rogers (and maybe less well-known for her encounter with Captain James T. Kirk). Koko’s sign-language training began in 1972 with then-graduate student Francine (Penny) Patterson of Stanford University. According to the Gorilla Foundation, Koko knows 1,000 signs and understands spoken English. It also claims the gorilla has an IQ somewhere between 70 and 95 (the average human IQ is 100). (Critics, however, remain skeptical about some of Koko’s supposed abilities due to the lack of recent scientific publications supporting the claims. (PDF))

Kanzi: Kanzi, a bonobo, doesn’t use sign language; he uses different combinations of lexigrams, or symbols, to communicate. In the early 1980s, psychologist Sue Savage-Rumbaugh, then of Georgia State University, was trying to teach Kanzi’s mom, Matata, to use the lexigrams; instead, Kanzi was the one who mastered the symbols. Kanzi understands spoken English and knows close to 400 symbols. When he “speaks,” his lexigram usage follows rules of grammar and syntax, according to researchers at the Great Ape Trust in Iowa, where Kanzi now resides. Kanzi is also an accomplished stone-tool maker.

Young male and female chimps may play differently (photo courtesy of flickr user Tambako the Jaguar)

Young female chimps that live in a Ugandan park sometimes treat sticks in the same ways a little girl might treat her dolly, according to a new study in the journal Current Biology.

Studies have shown that human girls tend to play more with dolls and boys with toy vehicles and fake weapons. Captive monkeys also show a tendency to split along gender lines when they play with sex-stereotyped toys, but there has been no evidence that any young wild animals that play with toys play differently depending on whether they or male or female.

Scientists have been watching and recording the activities of the Kanyawara chimpanzee community in Uganda’s Kibale National Park for 14 years. These chimps use sticks in four different ways: as probes in holes that might contain honey or water; as weapons; during play; or in a behavior the researchers have named “stick-carrying”:

Stick-carrying consisted of holding or cradling detached sticks. The juveniles carried pieces of bark, small logs or woody vine, with their hand or mouth, underarm or, most commonly, tucked between the abdomen and thigh. Individuals carried sticks for periods of one minute to more than four hours during which they rested, walked, climbed, slept and fed as usual.

The researchers say that the behavior is “suggestive of rudimentary doll play” and, as with humans, more common among young females than young males. They think that with stick-carrying, the young chimps are imitating their mothers. And unlike other behaviors that employ sticks, stick-carrying always ceased when a young female had a baby of her own.

Stick-carrying is rare among the Kanyawara chimps and has never been reported elsewhere. If the behavior is unique to this population, says study co-author Richard Wrangham of Harvard University, “it will be the first case of a tradition maintained just among the young, like nursery rhymes and some games in human children.”

Fifty years ago today, Jane Goodall arrived at Gombe Stream Chimpanzee Reserve (now Gombe National Park) in Tanzania and began documenting the lives of the chimpanzees that lived there. When Goodall ended her fieldwork to advocate for the chimps and the environment in general, other researchers took up the work, and the Gombe chimp research project is now one of the longest running studies of a population of wild animals. Since the study’s start in 1960, researchers have published more than 200 scientific papers about the chimps, including some of the most important discoveries about our primate cousins. Here are the top five:

Gombe chimps eating a red colobus monkey (courtesy of flickr user kibuyu)

1) Chimpanzees eat meat: Before Goodall began her studies in Gombe, most scientists thought that chimpanzees were vegetarians. That notion was quickly dropped after Goodall observed chimps eating what appeared to be a freshly killed piglet in October 1960. She would later observe chimps hunting young bush pigs and baby colobus monkeys.

2) Chimpanzees use tools: Goodall observed two chimps, David Greybeard and Goliath, using sticks to extract termites, the first instance of a non-human species using a tool. Gombe chimps also use sticks to catch army ants and use leaves to soak up water to drink and to clean themselves. Other chimps have been observed using stones to crack open nuts.

3) Chimpanzees engage in warfare: In 1974, the Gombe chimps split into two groups that then proceeded to battle for dominance for the next four years. This was the first instance of a non-human primate species engaging in long-term war.

4) Chimpanzees can be cannibals: In 1975, one female chimp, Passion, was observed killing another’s infant and sharing the meat with her daughter, Pom. The pair would continue their infant cannibalism for two years. A similar event has been observed among chimps in Uganda.

5) Chimpanzees have complex social relationships: Chimpanzees live in small groups of up to six individuals, and several of these smaller groups belong to a larger community of 40 to 60 chimps. The males, led by an alpha, dominate the group, while the females have their own hierarchy. Within those groups, there is a complex set of social interactions, a chimp “soap opera” almost, that has kept the Gombe researchers busy for the past five decades.