The way a baby chimpanzee gestures to her mother resembles how a human infant interacts with its mother. Photo by Flickr user Rennett Stowe

Thirteen years after the release of On the Origin of Species, Charles Darwin published another report on the evolution of mankind. In the 1872 book The Expression of the Emotions in Man and Animals, the naturalist argued that people from different cultures exhibit any given emotion through the same facial expression. This hypothesis didn’t quite pan out—last year, researchers poked a hole in the idea by showing that the expression of emotions such as anger, happiness and fear wasn’t universal (PDF). Nonetheless, certain basic things—such as the urge to cry out in pain, an increase in blood pressure when feeling anger, even shrugging when we don’t understand something—cross cultures.

A new study, published today in the journal Frontiers in Psychology, compares such involuntary responses, but with an added twist: Some observable behaviors aren’t only universal to the human species, but to our closest relatives too—chimpanzees and bonobos.

Using video analysis, a team of UCLA researchers found that human, chimpanzee and bonobo babies make similar gestures when interacting with caregivers. Members of all three species reach with their arms and hands for objects or people, and point with their fingers or heads. They also raise their arms up, a motion indicating that they want to be picked up, in the same manner. Such gestures, which seemed to be innate in all three species, precede and eventually lead to the development of language in humans, the researchers say.

To pick up on these behaviors, the team studied hree babies of differing species through videos taken over a number of months. The child stars of these videos included a chimpanzee named Panpanzee, a bonobo called Panbanisha and a human girl, identified as GN. The apes were raised together at the Georgia State University Language Research Center in Atlanta, where researchers study language and cognitive processes in chimps, monkeys and humans. There, Panpanzee and Panbanisha were taught to communicate with their human caregivers using gestures, noises and lexigrams, abstract symbols that represent words. The human child grew up in her family’s home, where her parents facilitated her learning.

Researchers filmed the child’s development for seven months, starting when she was 11 months old, while the apes were taped from 12 months of age to 26 months. In the early stages of the study, the observed gestures were of a communicative nature: all three infants engaged in the behavior with the intention of conveying how their emotions and needs. They made eye contact with their caregivers, added non-verbal vocalizations to their movements or exerted physical effort to elicit a response.

By the second half of the experiment, the production of communicative symbols—visual ones for the apes, vocal ones for the human—increased. As she grew older, the human child began using more spoken words, while the chimpanzee and bonobo learned and used more lexigrams. Eventually, the child began speaking to convey what she felt, rather than only gesturing. The apes, on the other hand, continued to rely on gestures. The study calls this divergence in behavior “the first indication of a distinctive human pathway to language.”

The researchers speculate that the matching behaviors can be traced to the last shared ancestor of humans, chimps and bobonos, who lived between four and seven million years ago. That ancestor probably exhibited the same early gestures, which all three species then inherited. When the species diverged, humans managed to build on this communicative capacity by eventually graduating to speech.

Hints of this can be seen in how the human child paired her gestures with non-speech vocalizations, the precursors to words, far more than the apes did. It’s this successful combination of gestures and words that may have led to the birth of human language.

A baby cao vit gibbon learns to search for food. Photo: Zhao Chao 赵超, Fauna and Flora International

You probably haven’t heard of the world’s second rarest ape, the cao vit gibbon. Scientists know of only one place the species still lives in the wild. In the 1960s, things got so bad for the cao vit gibbon that the species was declared extinct. But in 2002, to the surprise and elation of conservationists, the animals—whose shaggy coats can be a fiery orange or jet black—turned up along Vietnam’s remote northern border. Several years later, a few gibbons were found in China, too.

Also known as the eastern black-crested gibbon, the cao vit gibbons once covered an expanse of forest spanning from southern China and northern Vietnam just east of the Red River, but today only about 110 individuals survive. This gibbon is highly inclined to stick to the trees—in a previous study, during more than 2,000 hours spent observing gibbons in the field, researchers saw only once and very briefly one young male cao vit gibbon come down from the canopy and walk on a rock for a few seconds. Population surveys based on watching the animals in the branches reveal that the gibbons live in 18 groups scattered throughout the area. That makes it the second least populous species of ape, just after the Hainan gibbon, another type of extremely rare gibbon living in the same area of Asia.

In 2007 and 2009, Vietnam and then China hustled to establish special protected areas dedicated to preventing the cao vit gibbon’s extinction. Much of the area surrounding the remaining populations of gibbons is quickly being converted to agricultural fields and pasturesor cut down to make charcoal to sell and use at home, a common practice in the area. Hunting—though illegal—is also an issue, as exotic wild meat dinners are popular with locals in the region.

For an endangered species to recover rather than just survive, it needs to grow in numbers. But any given patch of land can only support so many animals given the amount of food and space that’s available. If populations exceed this threshold—called a carrying capacity—then animals will either starve, get picked off by predators or have to move somewhere else. 

Researchers from Dali University in Yunnan, the Chinese Academy of Sciences in Kunming and the Chinese Research Academy of Environmental Sciences in Beijing wanted to find out how much of the protected forest the cao vit gibbons had expanded into, and also how many animals that pocket of land could eventually support. To answer this question, they turned to high-resolution satellite images, describing their results in the journal Biological Conservation.

Once they acquired aerial images of the gibbons’ habitat, they classified it into forest, scrub, shrub land and developed areas. This was important because gibbons can only live high in forest canopies, meaning the latter three categories were out of bounds for potentially supporting the animals. Overall, the area could be divided into five different zones that were split apart by either roads or rivers. From there, the researchers plugged the data into computer models that ranked possible gibbon habitat from high to low quality.

Habitat quality over the five zones the researchers identified. Stars mark sites where gibbons currently live. Image from Fan et al., Biological Conservation

Their results revealed several bits of news, some good and some bad. First, from the models it seems that 20 groups of gibbons could eventually live in the protected forest areas before the population reaches its carrying capacity threshold. However, as human development creeps closer and closer, that disturbance could lower that figure. As things stand, the gibbons will likely reach their carrying capacity in the current habitat in 15 years, which doesn’t bode well for building up the species’ numbers.

There are a couple options. The protected area isn’t all great habitat, it turns out. Some of it is just mediocre for gibbons. If that span of forest could be improved, it could eventually support up to 26 groups of animals. The researchers also identified two other potential areas where gibbons could live if they could somehow manage to travel there (no gibbon has ever been known to cross a river or a road). But these patches of welcoming forest, located in Vietnam, are not protected, so they likely will not remain forests for long. If the government decided to protect those areas, the researchers write, they could serve as places for cao vit gibbons to live in the future, especially if narrow corridors of trees connecting the two areas were protected and restored as well.

If these patches of forest were protected, gibbons would not be the only species to benefit. Numerous other species of primates and monkeys, civets, pangolins, porcupines, birds, bats and many more depend upon those last remaining jungle habitats for survival. “In summary, the last remaining population of cao vit gibbon is nearing its carrying capacity in the current remaining forest patch,” the authors write. “Forest protection and active forest restoration using important food tree plantings to increase habitat quality and connectivity should be the most critical part of the ongoing conservation management strategy.”

This chimp may look innocent, but he may harbor any of dozens of diseases that infect humans. Photo by AfrikaForce

Anyone who has read a Richard Preston book, such as The Hot Zone or Panic in Level 4, knows the danger of tampering with wildlife. The story usually goes something like this: Intrepid explorers venture into a dark, bat infested cave in the heart of East Africa, only to encounter something unseen and living, which takes up residence in their bodies. Unknowingly infected, the happy travelers jump on a plane back to Europe or the States, spreading their deadly pathogen willy-nilly to every human they encounter upon the way. Those people, in turn, bring the novel virus or bacterium back home to strangers and loved ones alike. Before the world knows it, a pandemic has arrived.

This scenario may sound like fiction, but it’s exactly what infectious disease experts fear most. Most emerging infectious diseases in humans have indeed arisen from animals–think swine and bird flu (poultry and wild birds), SARS (unknown animals in Chinese markets), Ebola (probably bats) and HIV (non-human primates). Therefore, experts prioritize the task of figuring out which animals in which regions of the world are most prone to delivering the latest novel pathogen to hapless humanity.

With this in mind, researchers at Harvard University, the University of Granada and the University of Valencia set out to develop a new strategy for predicting the risk and rise of new diseases transmitted from animals before they happen, describing their efforts in the journal Proceedings of the National Academy of Sciences.

To narrow the hypothetical disease search down, the team chose to focus on non-human primates. Because monkeys and great apes are so closely related to us, their potential for developing and transmitting a pathogen suited to the human body is greater than the equivalent risk from animals such as birds or pigs. As a general rule, the more related species are, the greater the chances they can share a disease. The researchers gathered data from 140 species of primates. They overlaid that information with more than 6,000 infection records from those various primate species, representing 300 different pathogens, including viruses, bacteria, parasitic worms, protozoa, insects and fungus. This way, they could visualize which pathogens infect which species and where.

Like mapping links between who-knows-who in a social network, primates that shared pathogens were connected. This meant that the more pathogens an animal shared with other species, the more centrally located it was on the tangled web of the disease diagram.    

A diagram depicting shared parasites among primate species. Each bubble represents one species, with lines connecting species by shared pathogens. The larger the bubble, the more emerging infectious diseases that species harbors. The dark blue bubbles represent the top 10 primates that share the most emerging infectious diseases with humans. Photo by Gomez et al., via PNAS

From studying these charts, a few commonalities emerged. Animals at the center of the diagram tended to be those that lived in dense social groups and also covered a wide geographic range (yes, similar to humans). These species also tended to harbor parasites that are known to infect humans, including more pathogens identified as emerging infectious diseases. In other words, those species that occurred in the center of the diagram are the best positioned to kick off the next pandemic or horrific infectious disease, and thus should be the ones that experts should keep the closest watch on.

Such animals could qualify as “superspreaders,” or those that receive and transmit pathogens very often to other species.”The identification of species that behave as superspreaders is crucial for developing surveillance protocols and interventions aimed at preventing future disease emergence in human populations,” the authors write.

Apes appeared in the heart of the disease diagram and are among the species we should be most worried about, which is not surprising considering that diseases such as malaria and HIV first emerged from these animals. On the other hand, some non-ape primates, including baboons and vervet monkeys, also popped up in the center of the diagram and turn out to harbor many human emerging disease parasites. 

Currently, our ability to predict where, when and how new emerging infectious diseases might arise is “remarkably weak,” they continue, but if we can identify those sources before they become a problem we could prevent a potential health disaster on a regional or even global scale. This new approach for identifying animal risks, the authors write, could also be applied to other wildlife groups, such as rodents, bats, livestock and carnivores. “Our findings suggest that centrality may help to detect risks that might otherwise go unnoticed, and thus to predict disease emergence in advance of outbreaks—an important goal for stemming future zoonotic disease risks,” they conclude. 

Baby bonobos share papayas. Photo from Jingzhi Tan

In 1719, Daniel Defoe wrote in Robinson Crusoe, ”He declar’d he had reserv’d nothing from the Men, and went Share and Share alike with them in every Bit they eat.” Defoe’s famous sharing phrase has persisted throughout the years, passing from parent to child as a lesson on the virtues of sharing with family, peers and even strangers.

But in the context of evolution and survival of the fittest, sharing makes no sense. Until now, scientists assumed that humans alone subscribed to this behavior, especially when it comes to sharing with strangers, and wrote the trait off as a quirk stemming from our unique cognitive and social development.

Sure, primatologists know that great apes help and voluntarily share food with other group mates (acts that indirectly benefits themselves). But strangers? Such a behavior is unheard of amidst species that often compete aggressively with other groups and even murder foreign individuals.

Researchers from Duke University decided to challenge the great ape’s bad sharing rep, seeking to discover whether or not our furry relatives may also have a propensity for partitioning goods with animals they do not know. The scientists chose bonobos–a type of great ape sometimes referred to as a pygmy chimpanzee–for their study. Compared to chimpanzees, bonobos possess a relatively high tolerance for strangers, so they seemed like a logical candidate for investigations into the nature of sharing.

At a bonobo sanctuary in the Democratic Republic of the Congo, they enrolled 15 wild-born bonobos orphaned and rescued from the illegal wildlife trade in four experiments. In the first experiment, the researchers led a bonobo into a room piled high with delicious banana slices. Behind two sliding doors, they placed either a friend of the main bonobo or a stranger (a bonobo unrelated and unknown to their main research subject). The bonobo with the bananas could chose to eat the food all on its own, or open the sliding door and invite both or either the friend or stranger to join in. In the second experiment, they placed only one bonobo–either the friend or stranger–behind a door and left the second room empty.

The results, which they describe this week in the journal PLoS One, confounded the researchers. In more than 70 percent of the trials, the bonobos shared their food at least once. They preferred to release the stranger over their group mate, and the stranger in turn often released the other bonobo, even though that meant splitting the food three ways and being outnumbered by two bonobos that already knew each other. They ignored the door leading to the empty room, showing that the novelty of opening the door was not motivating their behavior.

So, were the bonobos willing to share their food with strangers because of an overwhelming desire to interact with the unknown apes, or were they motivated by a sense of altruism? The researchers set up two more experiments to find out. They arranged a rope which, when pulled, released either a bonobo stranger or friend into a room which held more bananas. A mesh divider separated the main bonobo from that room, however, meaning it could neither reach the food or interact directly with the released ape. Even when there was no immediate social or culinary reward on offer, the researchers found, 9 out of 10 bonobos still chose to release their friend or the stranger at least once, allowing the other ape to reach the banana reward.

Bonobos drew the line, however, in the final experiment. This setup allowed both bonobos to access the food, but did not let them interact physically with the stranger or friend. In other words, the main bonobo would have to forfeit some of its food but receive no reward of sniffing, petting or playing with another ape. None of the bonobos chose to open the door, suggesting that the seemingly altruistic sharing of the first two experiments was just a ploy to gain gratifying access to intriguing strangers and, to a lesser extent, friends. The third experiment, however, shows that the bonobos’ motivations are not completely selfish. When the food was so far out of reach that they themselves could not benefit, they allowed a friend or stranger to enjoy it instead.

Bonobos, in other words, break the rules when it comes to sharing, showing that kindness towards strangers is not unique to humans. Oddly enough, unlike their bipedal counterparts, bonobos even seem to prefer strangers to group mates. This behavior, the study authors think, might have evolved to help groups of bonobos expand their social networks. Further investigations may lend clues about evolution of sharing in humans.

“Like chimpanzees, our species would kill strangers; like bonobos, we could also be very nice to strangers,” said Jingzhi Tan, an evolutionary anthropologist at Duke University and lead author of the paper, in a statement. “Our results highlight the importance of studying bonobos to fully understand the origins of such human behaviors.”

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.

By stimulating neural activity with electrodes, researchers boosted the mental skills of rhesus monkeys under the influence of cocaine. Image via Wikimedia Commons/J.M. Garg

Over the past year, we’ve seen the invention of increasingly sophisticated prosthetic limbs, ears and eyes—ideas and inventions that once seemed so fanciful as to belong to the realm of science fiction. Now, a team of scientists at Wake Forest University in North Carolina is going one step further, working on developing a prosthesis for the most complex organ of all: the mind.

As revealed in a paper published today in the Journal of Neural Engineering, the researchers created a way to manipulate the neural activity of rhesus monkeys to assist them with decision-making when their cognitive abilities were impaired due to the administration of cocaine. The scientists say their research could someday lead to a new way of assisting people who have diminished cognitive ability to disease or injury.

To establish a baseline for the monkeys’ decision-making abilities, the researchers trained them to execute a simple matching task on a computer. As each of the five monkeys used in the study looked at a computer screen, they were shown a single clip-art image, then the screen went blank for a minute or two. Afterward, the original picture came back, along with one to seven other images.

At the same time, the position of the monkeys’ arms on the countertop in front of the computer was tracked via a camera that detected UV light, which bounced off of a special reflector affixed to the back of the monkeys’ hands. The position of their hands, as detected by the camera, was digitized and fed into the computer, so when they moved their hands, a cursor on the computer screen moved, as though they were holding a mouse.

When the images came back onto the computer screen after the blank interval, if the monkeys moved the cursor over the original picture they’d been shown, they were rewarded with a drop of juice via a sipper situated near their mouths. Over the course of several months, each monkey got the hang of the task and trained until they were able to select the correct image 40 to 75 percent of the time, depending on the number of photos shown.

While they were doing the matching, though, the researchers were closely monitoring the monkeys’ neural patterns with recording cylinders that had been implanted in the animals’ prefrontal cortex, an area of the brain known to be active during decision-making tasks. The scientists discovered that the same neural activity patterns reliably occurred in this area whenever the monkeys successfully completed the task and less frequently when the monkeys picked the wrong picture.

Next, things got interesting: As the monkeys looked at the images and sipped juice, the researchers surreptitiously injected each one with cocaine. Because the drug is known to disrupt the sort of continued concentration and decision-making skills necessary to getting the computer matching task correct, the monkeys’ success rates predictably dwindled, and they picked the correct image 13 percent less frequently than before they were administered cocaine.

When the researchers used the electrodes they had previously implanted in the monkeys’ brains–located in the precise locations inside the prefrontal cortex that had been firing reliably when they correctly matched the image–to later trigger those neurons, replicating the firing patterns, the results were dramatic.

“The prosthetic device is like ‘flipping a switch’ to turn on a decision in real time,” said Sam Deadwyler, a professor of physiology and pharmacology at Wake Forest and one of the study’s authors. Under the influence of cocaine, the prosthesis restored and even improved as compared with the baseline, with the monkeys selecting the correct image 10 percent more frequently than before.

“Based on the findings of this study, we hope in the future to develop an implantable neuroprosthesis that could help people recover from cognitive deficiencies due to brain injuries,” said Wake Forest professor Robert E. Hampson, the lead author of the study.

It’s conceivable, though, that the temptation of a neural prostheses could be strong enough to someday appeal to a different crowd—instead of those who suffered a stroke or lesion, people simply looking for a competitive edge. It might sound far-fetched, but in an age of “neuroenhancing” drugs and ever-increasing plastic surgery, there’s no telling where the concept of neural prosthetics might go.

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.

Scientists are still trying to figure out why primates have excellent vision. (langur monkey photo courtesy of flickr user Troup Dresser)

We humans aren’t alone in our aversion to snakes. Our primate cousins also fear serpents. And for good reason—snakes eat primates. Snakes have been preying on primates for millions of years, and some researchers think they might be the reason we—and our fellow primates—have such good eyesight.

Good vision is a hallmark of the primate order. Compared with many other mammals, primates have more closely spaced, forward-facing eyes that allow for a lot of overlap between each eye’s visual field, which in turn gives primates 3-D, or stereoscopic, vision and a good sense of depth perception.

In the early 20th century, scientists attributed primates’ keen sense of sight to their arboreal lifestyle. The ancestors of primates needed to accurately judge the distances between tree branches before taking a leap, so the theory went. But that hypothesis lost favor in the 1970s after biological anthropologist Matt Cartmill, now at Boston University, pointed out that many other acrobatic, tree-dwelling animals like squirrels get by without such an advanced visual system.

Cartmill offered his own explanation, called the “visual predation hypothesis”: early primates needed superb visual skills to hunt and grab insects. Another hypothesis is that primates needed to see well to pluck fruits from the ends of tree branches.

More recently, snakes came into the picture. In 2006, anthropologist Lynne Isbell of the University of California at Davis argued that early primates were stalked by constricting snakes, and it was highly beneficial to see these camouflaged predators before it was too late. Later, some monkeys and apes in Africa and Asia started to live alongside venomous snakes, which led to even more visual advancements.

But the idea may not hold up, according to the authors of a recent study in the Journal of Human Evolution. Led by behavioral ecologist Brandon Wheeler of the Cognitive Ethology Laboratory at the German Primate Center, the team tested the snake hypothesis by looking at variations in modern primates’ visual skills (in terms of stereoscopic vision, as measured by the closeness of the eyes) to see if the primates with the best eyesight had the longest evolutionary history of coexisting with snakes and the greatest likelihood of encountering and being attacked by them.

The team didn’t find any correlations between snake exposure and primate vision, concluding that snake attacks did not drive the evolution of better eyesight. Still, the researchers say, detecting snakes was definitely a beneficial side effect regardless of why better vision evolved.

A bonobo at Twycross Zoo (courtesy of flickr user GraphicReality)

Chimpanzees may announce with a grunt when they’ve found food, but bonobos also tell their compatriots when that food find is a good one, say scientists reporting in PLoS ONE.

When bonobos encounter a favorite food, like kiwi, they emit a series of long barks and short peeps. If that food is, say, an apple and not as well-liked, a bonobo makes other sounds, lower pitched yelps and peep-yelps. Researchers at the University of St Andrews in Scotland set out to discover whether other bonobos are able to extract information from those vocalizations. They studied four of the animals at the Twycross Zoo in central England.

The researchers started by training the bonobos that they would find kiwis on one side of their enclosure and apples on the other. In the morning, one group of animals would be let into the enclosure, and their responses to one of the fruits were recorded. That response was played later in the day when the second group of bonobos was let out. If the kiwi call was played, the bonobos were more likely to visit the kiwi side, and if the apple call was played, they were more likely to visit the apple side. If the call wasn’t clear, then the animals were also more confused in their foraging.

“These animals are highly intelligent and this kind of study highlights their ability to extract meaning from listening to each other’s vocalisations,” study co-author Zanna Clay told BBC News.

This doesn’t mean that bonobos have their own language—their communications lack syntax and structure—but “the way that the listening bonobos interpreted these sequences as meaningful shows some similarities with how we listen to language and understand it,” Clay said.

Richard Branson will bring 30 ring-tailed lemurs to Mosquito Island in a few weeks (image courtesy of flickr user Kabacchi)

When billionaire Richard Branson announced the construction of a luxury eco-resort in the British Virgin Islands, it sounded like a great idea. But his latest plan to populate one of those islands, Mosquito Island, with endangered lemurs, sounds more like a crazy-rich-man idea.

There are about 100 species of lemurs, a type of small primate native to the island of Madagascar. Most are classified as vulnerable, endangered or critically endangered and are threatened by deforestation, hunting and the exotic pet trade. Those threats have only increased during the political unrest of the last two years.

But will importing lemurs to Mosquito Island help those species? Or could there be ecological heartbreak in store?

Branson will start by bringing 30 ring-tailed lemurs to the island from zoos in Canada, South Africa and Sweden in a few weeks. They’ll be kept in cages to acclimatize before being released into the forest. They’ll be inoculated against diseases, and veterinarians will be available to treat sick lemurs. Releases of red-ruffed lemurs and sifakas may follow, according to reports.

When I asked Erik Patel, who studies silky safakas, about the plans, he said that the ring-tailed lemurs at least stand a chance of surviving their introduction to the island. “They are quite flexible,” he says. But, “it would certainly be a grave mistake to bring sifakas there, since sifakas are known to be amongst the most sensitive lemurs, are difficult to rear in captivity, and seldom survive reintroductions.”

And then there’s the question of what will happen to all the plants and creatures that already live on that island. Conservation plans rarely begin with (or even include) the introduction of a non-native species. And though lemurs surely are adorable, they “could damage native flora and fauna on the island, particularly reptiles such as the stout iguana, turnip-tailed gecko, and dwarf gecko, as well as birds’ eggs,” Patel says.

Even if the introduction of lemurs to Mosquito Island is ultimately successful and does no harm to the local ecology, it’s difficult to see how this will help the lemurs of Madagascar. Branson has said that his lemurs might eventually be reintroduced to their homeland, but there are already established projects that do so.

Branson has a good reputation for supporting the environment, pledging $3 billion towards biofuel research, for example, sponsoring a prize for climate change research, and even funding sifaka conservation efforts in Madagascar. “I think he does care about these animals, and basically wants to help them,” Patel says. “However, in this case, the risks may outweigh the benefits. I hope we can continue to channel his energy and sincere goodwill into further conservation projects in Madagascar itself, which may be a bargain compared to the high cost of purchasing and transporting all these lemurs to Mosquito Island.”

A young gorilla in the Hirwa group in Rwanda, 2009 (courtesy of flickr user petercolesdc)

On the one hand, it’s pretty amazing that I can find images of a specific mountain gorilla family in Rwanda through a simple Flickr search. But the availability of those photos comes from the numerous visits of humans to the national parks in Congo, Rwanda and Uganda where the world’s remaining 786 mountain gorillas live, and those visits may have a deadly downside for the gorillas: respiratory infections from human viruses.

Mountain gorillas (Gorilla berengei berengei) live only in the mountainous region where Congo, Rwanda and Uganda meet, and their small numbers make them vulnerable to extinction. To make matters worse, they are sandwiched between some of the most populous areas of Africa, and threatened by habitat destruction and poaching. A lesser known problem is infectious disease, which is the second biggest cause of death for the gorillas, after trauma, and accounts for one fifth of all sudden deaths.

And now a study in the journal Emerging Infectious Diseases documents two gorilla deaths from the human metapneumovirus (HMPV) in 2009. During that summer, the Hirwa family of gorillas in Rwanda experienced an outbreak of respiratory disease; 11 of the 12 animals experienced symptoms including coughing, nasal discharge and lethargy. Veterinarians from the Mountain Gorilla Veterinary Project treated five of the gorillas with antimicrobial drugs, but an untreated adult female and a 3-day-old male died. Analyses of the remains revealed that both individuals had been infected with HMPV, though the adult female died of a secondary bacterial pneumonia infection. The HMPV infection likely predisposed her to pneumonia, the researchers say.

“Because there are fewer than 800 living mountain gorillas, each individual is critically important to the survival of their species,” said Mike Cranfield, executive director of the Mountain Gorilla Veterinary Project. “But mountain gorillas are surrounded by people, and this discovery makes it clear that living in protected national parks is not a barrier to human diseases.”

The source of the HMPV is unknown, and the two animals that died had not been handled by any of the veterinarians or park staff during the course of their illness. But with the human population ever encroaching and tourists visiting them in their mountain homes, it seems better strategies are needed to protect the gorillas from human diseases.

A couple of years ago, the magazine profiled Yale psychologist and primate researcher Laurie Santos and her work studying a colony of rhesus macaques on Cayo Santiago, an island off the coast of Puerto Rico (read “Thinking Like a Monkey“).

She has built a growing and impressive list of publications in cognitive neuroscience (mostly having to do with how primates understand physical objects and relations) and evolutionary psychology, the field that grew out of sociobiology. “If you see something in a primate,” Santos reasons, “you can use it as a window into the evolutionary past of human beings.”

More recently, Santos gave a TEDTalk (above) on another aspect of her research in which she taught brown capuchin monkeys to use money. No, not so they could run her errands at the local shop, but so that she could learn about how we humans got ourselves into our latest financial mess.

See, if monkeys make the same financial mistakes we do, if they have the same biases, then it might prove a bit harder to prevent situations like the latest recession. Santos explains in the video:

[W]hat we’ve learned is that these biases might be a deeper part of us than that. In fact, they might be due to the very nature of our evolutionary history. You know, maybe it’s not just humans at the right side of this chain that’s duncey. Maybe it’s sort of duncey all the way back. And this, if we believe the capuchin monkey results, means that these duncey strategies might be 35 million years old.

It’s rather sad to think that we might be doomed to repeat the same financial decisions over and over because they are so ingrained into our human makeup that even our distant monkey cousins make the same bad decisions. But Santos also points out that if we know we do these things—that we have these biases and can’t just easily put them aside—then we can use technology and other work-arounds to overcome our limitations.

If we can create a monkey marketplace, surely we can figure out how to get our own to work better.

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.

Are you more like a bonobo (above) or a chimp? (via wikimedia commons)

Bonobos and chimpanzees may look alike, but behaviorally they are very different. Chimps are aggressive and warlike, and males dominate. Bonobos are more peaceful and tolerant and females rule. These two primate species are our closest living relatives (we share nearly 99 percent of our DNA), and humans share traits with both species. Some people are more like bonobos, and others more like chimpanzees.

A new study published this week in PNAS shows that most human males are hormonally similar to bonobos when in a competitive scenario, but those men striving for a high status are more like chimps.

The biologists conducting the study began by documenting changes in the levels of two hormones—cortisol and testosterone—in 12 pairs of bonobos and 24 pairs of chimpanzees presented with a situation in which they had to compete for food. The scientists used cotton swabs dipped in Sweet Tart dust (Sweet Tarts stimulate saliva production in primates) to collect saliva before and after the pairs were presented with a pile of food.

Previous research has shown that when human males are faced with a competition of some sort, your average guy will experience increases in levels of glucorticoids like cortisol. Men who are striving for a high status, however, exhibit increases in testosterone levels. And when the competition is over, winners (of either type) have an increase in testosterone and losers a decrease.

Bonobos are like the average guy, according to this new study. Prior to competition, they experience an increase in cortisol, which is associated with stress and a passive coping strategy. Chimps are like the men striving for power; their testosterone levels increase prior to competition and they react as if the situation is a threat to their status.

But humans are the only primate species out of the three to experience changes in hormone levels after the competition is over. ‘It’s exciting because we can see that in some ways we’re similar to bonobos, in others we’re similar to chimpanzees,” says Brian Hare of Duke University. “But then there’s also a part of our biology that seems to be entirely unique.”

Bonobo Handshake, by Vanessa Woods

I once told a friend about bonobos—”they’re like chimpanzees,” I said, “but they’re peaceful and have sex all the time”—and he thought I was making them up. My computer doesn’t think they exist either; it suggests alternative spellings including “bonbons” and “bongos.” Bonobos are our closest living primate cousins (along with chimpanzees), sharing 98.7 percent of their DNA with us, but most people don’t know anything about them.

Chimpanzees have been studied longer and there are more of them: Bonobos weren’t discovered until 1933, 150 years after their better-known cousins. And there are only some 10,ooo to 40,000 bonobos in the wild (about one-tenth the chimpanzee population), all in the Democratic Republic of Congo, which makes them more endangered than chimps. Bonobos have also lacked a Jane Goodall or a Dian Fossey to champion their cause, and there are few books about them.

Now there is a new book, Bonobo Handshake, by Vanessa Woods. Woods mixes bonobo science with her own personal tale. She meets, falls in love with (and later marries) a young primatologist, Brian Hare, and follows him to Congo, one of the most dangerous places on the planet (the U.S. State Department warns of armed rebels, kidnappings and deadly diseases). They go to Lola Ya Bonobo, a sanctuary for young bonobos orphaned by the bushmeat trade or rescued from being pets. Hare was there to learn more about the bonobos and discover how they differed from their chimpanzee cousins. Woods, a journalist, was just along for the ride at first but she was quickly drafted as research assistant to Hare when it turned out that the bonobos trusted only women.

The story follows Woods and Hare through research experiments, moves from country to country and even during marital spats. Woods eventually finds her purpose: saving the bonobos. She helps to care for the sanctuary’s orphans. She works with the organization, Friends of the Bonobos, that runs Lola. And she eventually becomes a research scientist in her own right.

Woods’ tale is interspersed with plenty of information about bonobos and how they interact with each other. Bonobos easily share and cooperate, unlike chimpanzees. They like to eat slowly and love sugarcane. They are afraid of doors. Despite their peaceful nature, they can still be mean or jealous or violent. Young bonobos can be very fragile. And yes, they really do have sex all the time, though not as often in the wild as in a zoo.

The book also details the (so far mostly successful) attempt to reintroduce the rescued bonobos back into the wild, an incredible feat in a country torn by violence. (Woods gives one of the best accounts I’ve read of Congo’s history and the effect of that violence on the people who live there.) Last June, nine bonobos were transferred to a site near the village of Basankusu. The local people work as trackers and administrative staff. The bonobos have brought jobs, schools and a clinic to the villagers.

It’s easy to look at a country like Congo and wonder whether the money spent on cute furry primates would be better put to use on food or medicine for an impoverished population. But saving wildlife can have benefits for the local people, too, as evidenced by the bonobo reintroduction. And the bonobos may have even more important lessons for us. Scientists keep trying to answer the question of what makes us human. They look to our own species, of course, and to our ancestors and our primate relatives. “Most of the time, bonobos have no hunger, no violence, no poverty. And for all of our intelligence, all of our things, bonobos have the most important of all possessions—peace,” Woods writes. “If we lose bonobos, we will never learn their secret. And even more tragically, because they share so much of what makes us human, we will never understand ourselves.”