Science
Remembrances of apes past: Chimpanzees and bonobos can recognize long-lost friends
Not long ago, comparative psychologist Christopher Krupenye and a colleague visited the Leipzig Zoo in Germany, where both had worked on a research project several years before.
The 145-year-old zoo gets roughly 2 million visitors per year, and its bonobos are used to a parade of human faces passing their enclosure. But as Krupenye and his colleague approached, a male named Jasongo appeared to recognize them from a distance. He came bounding over, his jaw extended in the open-mouthed facial expression bonobos make at play, emitting the laughter-like sounds of a happy ape.
“When you return, it really seems like they really remember you,” said Krupenye, an assistant professor of psychological and brain sciences at Johns Hopkins University. “They’re experiencing dozens or hundreds of unfamiliar zoo guests every day who they largely ignore, and when you show up they come over and respond to their name.”
For humans, memory is essential to maintaining our complex web of social relationships. We have to remember who is a friend and who is a foe; who can be counted on for loyalty and who royally screwed you over during the last struggle for dominance.
Bonobos and chimpanzees, our closest living relatives, maintain similar social dynamics. Like us, they live in what scientists call “fission-fusion” societies, meaning they frequently split up to collect food and other resources before joining up again.
We shared a common ancestor roughly 5 million to 7 million years ago, a heartbeat in evolutionary time. Our genomes are about 99% identical.
Given these similarities, researchers have long suspected that chimps and bonobos have a robust capacity for social memory just as humans do. But unlike battles between rivals or grooming behaviors among friends, it’s hard to observe the act of an ape’s remembering.
“They have long-lasting social relationships that are really important for their survival and well-being,” said Laura Simone Lewis, a biological anthropologist and comparative psychologist who is a postdoctoral fellow at UC Berkeley. “It would make sense that they then have capacities to foster and maintain these social relationships for decades as well. We think that one capacity that helps them with that is being able to remember individuals.”
Lewis, Krupenye and their colleagues set out to record evidence of social memory in nonhuman primates. They used the same tool scientists often employ as a proxy for attention in human studies: eye tracking.
Sure enough, they found that the apes spent significantly more time studying images of former groupmates compared with photos of strangers. When presented with a picture of an individual they had shared a positive relationship with, they lingered even longer.
“Chimpanzees and bonobos were looking longer at the images of their previous groupmates with whom they had these more positive social relationships, or something like you might call their friends,” Lewis said.
The researchers looked at four populations of apes in three different sites: chimpanzees at Scotland’s Edinburgh Zoo, bonobos at Planckendael Zoo in Belgium, and chimps and bonobos at Kumamoto Sanctuary in Japan.
Participation in the study was entirely voluntary: Researchers showed the images only to animals who chose to wander over to the research area attached to their enclosure.
To entice potential research subjects, the scientists offered an enticement that has reliably worked among Homo sapiens: free drinks. A window in the research area was fitted with a nozzle that dispensed a tasty juice to any animal who came by for a sip.
In addition to attracting study subjects, the nozzle kept animals’ heads in a steady, forward-facing position. Researchers then showed the animals a screen with two side-by-side photos: one a former groupmate, and one an unknown ape of the same sex and approximate age. Three such pairs of photos flashed in sequence for three seconds each, each with a once-familiar face next to that of a stranger.
The study team then tracked the animals’ eye movements to precisely measure the amount of time they spent looking at each image, using technology previously deployed in human studies.
“Their eyes are so similar to ours that you can actually use the exact same machines,” Lewis said.
The 26 apes who participated in the study saw 16 to 32 pairs of images each. On average, they looked 14% longer at the animals they once knew, the researchers reported Monday in the Proceedings of the National Academy of Sciences.
The authors expected the quality of the chimps’ and bonobos’ memories would degrade over time, but that wasn’t the case. The apes’ focus on former groupmates was equally intent if they had been separated for two years or 10.
The study also documented the longest memory so far recorded in a nonhuman animal.
Louise is a bonobo at Kumamoto Sanctuary who had been transferred there 26 years earlier from the San Diego Zoo. (Members of captive ape populations are often moved to new facilities to prevent inbreeding and to mimic social patterns in the wild, where females of reproductive age will frequently transfer groups, Lewis said.)
On eight separate occasions, Louise was presented with images of her sister Loretta or nephew Erin. Each time she stared at her relatives for significantly longer than the average look of recognition.
“For at least 5 million years social beings like us have roamed this planet remembering events and individuals from their complicated social lives that in many ways are as deeply meaningful and political as our own,” said Brian Hare, an evolutionary anthropologist at Duke University who was not involved with the study.
“Our shared ancestors with other apes undoubtedly had remarkable memory because we see here that other living ape relatives, like our own species, can remember for decades details about their social relationships.”
Other researchers said the findings resonated with their personal observations of ape behavior.
“I am not surprised that the research indicated that bonobos and chimpanzees possess an enduring memory for previous social partners,” said Arizona State University anthropologist Kevin Langergraber, who is co-director of the Ngogo Chimpanzee Project in Uganda’s Kibale National Park.
“In fission-fusion species some members of a group may not see each other for several weeks or months, perhaps even years,” Langergraber said. “But during reunification after these long separations, the individuals will treat each other as group members rather than as strangers.”
While the findings support the theory that apes have sturdy social memories, the study’s design leaves some unanswered questions about the quality of those memories, Krupenye said. We can’t know if the pictures evoked the uncanny feeling of seeing a familiar face you can’t quite place, or if the image of a former groupmate unleashed a flood of nostalgia for their time together.
Science
Cluster of farmworkers diagnosed with rare animal-borne disease in Ventura County
A cluster of workers at Ventura County berry farms have been diagnosed with a rare disease often transmitted through sick animals’ urine, according to a public health advisory distributed to local doctors by county health officials Tuesday.
The bacterial infection, leptospirosis, has resulted in severe symptoms for some workers, including meningitis, an inflammation of the brain lining and spinal cord. Symptoms for mild cases included headaches and fevers.
The disease, which can be fatal, rarely spreads from human to human, according to the U.S. Centers for Disease Control and Prevention.
Ventura County Public Health has not given an official case count but said it had not identified any cases outside of the agriculture sector. The county’s agriculture commissioner was aware of 18 cases, the Ventura County Star reported.
The health department said it was first contacted by a local physician in October, who reported an unusual trend in symptoms among hospital patients.
After launching an investigation, the department identified leptospirosis as a probable cause of the illness and found most patients worked on caneberry farms that utilize hoop houses — greenhouse structures to shelter the crops.
As the investigation to identify any additional cases and the exact sources of exposure continues, Ventura County Public Health has asked healthcare providers to consider a leptospirosis diagnosis for sick agricultural workers, particularly berry harvesters.
Rodents are a common source and transmitter of disease, though other mammals — including livestock, cats and dogs — can transmit it as well.
The disease is spread through bodily fluids, such as urine, and is often contracted through cuts and abrasions that contact contaminated water and soil, where the bacteria can survive for months.
Humans can also contract the illness through contaminated food; however, the county health agency has found no known health risks to the general public, including through the contact or consumption of caneberries such as raspberries and blackberries.
Symptom onset typically occurs between two and 30 days after exposure, and symptoms can last for months if untreated, according to the CDC.
The illness often begins with mild symptoms, with fevers, chills, vomiting and headaches. Some cases can then enter a second, more severe phase that can result in kidney or liver failure.
Ventura County Public Health recommends agriculture and berry harvesters regularly rinse any cuts with soap and water and cover them with bandages. They also recommend wearing waterproof clothing and protection while working outdoors, including gloves and long-sleeve shirts and pants.
While there is no evidence of spread to the larger community, according to the department, residents should wash hands frequently and work to control rodents around their property if possible.
Pet owners can consult a veterinarian about leptospirosis vaccinations and should keep pets away from ponds, lakes and other natural bodies of water.
Science
Political stress: Can you stay engaged without sacrificing your mental health?
It’s been two weeks since Donald Trump won the presidential election, but Stacey Lamirand’s brain hasn’t stopped churning.
“I still think about the election all the time,” said the 60-year-old Bay Area resident, who wanted a Kamala Harris victory so badly that she flew to Pennsylvania and knocked on voters’ doors in the final days of the campaign. “I honestly don’t know what to do about that.”
Neither do the psychologists and political scientists who have been tracking the country’s slide toward toxic levels of partisanship.
Fully 69% of U.S. adults found the presidential election a significant source of stress in their lives, the American Psychological Assn. said in its latest Stress in America report.
The distress was present across the political spectrum, with 80% of Republicans, 79% of Democrats and 73% of independents surveyed saying they were stressed about the country’s future.
That’s unhealthy for the body politic — and for voters themselves. Stress can cause muscle tension, headaches, sleep problems and loss of appetite. Chronic stress can inflict more serious damage to the immune system and make people more vulnerable to heart attacks, strokes, diabetes, infertility, clinical anxiety, depression and other ailments.
In most circumstances, the sound medical advice is to disengage from the source of stress, therapists said. But when stress is coming from politics, that prescription pits the health of the individual against the health of the nation.
“I’m worried about people totally withdrawing from politics because it’s unpleasant,” said Aaron Weinschenk, a political scientist at the University of Wisconsin–Green Bay who studies political behavior and elections. “We don’t want them to do that. But we also don’t want them to feel sick.”
Modern life is full of stressors of all kinds: paying bills, pleasing difficult bosses, getting along with frenemies, caring for children or aging parents (or both).
The stress that stems from politics isn’t fundamentally different from other kinds of stress. What’s unique about it is the way it encompasses and enhances other sources of stress, said Brett Ford, a social psychologist at the University of Toronto who studies the link between emotions and political engagement.
For instance, she said, elections have the potential to make everyday stressors like money and health concerns more difficult to manage as candidates debate policies that could raise the price of gas or cut off access to certain kinds of medical care.
Layered on top of that is the fact that political disagreements have morphed into moral conflicts that are perceived as pitting good against evil.
“When someone comes into power who is not on the same page as you morally, that can hit very deeply,” Ford said.
Partisanship and polarization have raised the stakes as well. Voters who feel a strong connection to a political party become more invested in its success. That can make a loss at the ballot box feel like a personal defeat, she said.
There’s also the fact that we have limited control over the outcome of an election. A patient with heart disease can improve their prognosis by taking medicine, changing their diet, getting more exercise or quitting smoking. But a person with political stress is largely at the mercy of others.
“Politics is many forms of stress all rolled into one,” Ford said.
Weinschenk observed this firsthand the day after the election.
“I could feel it when I went into my classroom,” said the professor, whose research has found that people with political anxiety aren’t necessarily anxious in general. “I have a student who’s transgender and a couple of students who are gay. Their emotional state was so closed down.”
That’s almost to be expected in a place like Wisconsin, whose swing-state status caused residents to be bombarded with political messages. The more campaign ads a person is exposed to, the greater the risk of being diagnosed with anxiety, depression or another psychological ailment, according to a 2022 study in the journal PLOS One.
Political messages seem designed to keep voters “emotionally on edge,” said Vaile Wright, a licensed psychologist in Villa Park, Ill., and a member of the APA’s Stress in America team.
“It encourages emotion to drive our decision-making behavior, as opposed to logic,” Wright said. “When we’re really emotionally stimulated, it makes it so much more challenging to have civil conversation. For politicians, I think that’s powerful, because emotions can be very easily manipulated.”
Making voters feel anxious is a tried-and-true way to grab their attention, said Christopher Ojeda, a political scientist at UC Merced who studies mental health and politics.
“Feelings of anxiety can be mobilizing, definitely,” he said. “That’s why politicians make fear appeals — they want people to get engaged.”
On the other hand, “feelings of depression are demobilizing and take you out of the political system,” said Ojeda, author of “The Sad Citizen: How Politics is Depressing and Why it Matters.”
“What [these feelings] can tell you is, ‘Things aren’t going the way I want them to. Maybe I need to step back,’” he said.
Genessa Krasnow has been seeing a lot of that since the election.
The Seattle entrepreneur, who also campaigned for Harris, said it grates on her to see people laughing in restaurants “as if nothing had happened.” At a recent book club meeting, her fellow group members were willing to let her vent about politics for five minutes, but they weren’t interested in discussing ways they could counteract the incoming president.
“They’re in a state of disengagement,” said Krasnow, who is 56. She, meanwhile, is looking for new ways to reach young voters.
“I am exhausted. I am so sad,” she said. “But I don’t believe that disengaging is the answer.”
That’s the fundamental trade-off, Ojeda said, and there’s no one-size-fits-all solution.
“Everyone has to make a decision about how much engagement they can tolerate without undermining their psychological well-being,” he said.
Lamirand took steps to protect her mental health by cutting social media ties with people whose values aren’t aligned with hers. But she will remain politically active and expects to volunteer for phone-banking duty soon.
“Doing something is the only thing that allows me to feel better,” Lamirand said. “It allows me to feel some level of control.”
Ideally, Ford said, people would not have to choose between being politically active and preserving their mental health. She is investigating ways to help people feel hopeful, inspired and compassionate about political challenges, since these emotions can motivate action without triggering stress and anxiety.
“We want to counteract this pattern where the more involved you are, the worse you are,” Ford said.
The benefits would be felt across the political spectrum. In the APA survey, similar shares of Democrats, Republicans and independents agreed with statements like, “It causes me stress that politicians aren’t talking about the things that are most important to me,” and, “The political climate has caused strain between my family members and me.”
“Both sides are very invested in this country, and that is a good thing,” Wright said. “Antipathy and hopelessness really doesn’t serve us in the long run.”
Science
Video: SpaceX Unable to Recover Booster Stage During Sixth Test Flight
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