Zarin Machanda, Tufts University and Kris Sabbi, Harvard University

Wild chimpanzees have been studied for more than 60 years, but they continue to delight and surprise observers, as we found during the summer of 2017 in Kibale National Park in Uganda.

We were observing young chimpanzees' play to better understand how they grow up. For most group-living animals, play is an integral component of development. Beyond just having fun, social play allows them to practice critical physical and social skills they will need later in life.

But that summer, we realized that it wasn't just the young ones playing. Adults were joining in on play more often than we had seen before, especially with each other. Watching fully grown female chimpanzees tickling each other and laughing surprised even the most veteran researchers of our project.

What made this so unusual was not that adult chimpanzees were playing at all, but that they were doing it so frequently. A behavior that we typically might see once every week or two became something that we saw every day and sometimes lasted for hours.

So what had changed that summer? For us, as primatologists, this is where the fun began.

Why would adults play in the first place?

Scientists tend to think the main reason play declines with age is that individuals essentially grow out of it as they master motor and social skills and shift toward more adult behaviors. By this logic, adults only rarely play because they no longer need to. The situation is different for domesticated species like dogs because the process of domestication itself preserves juvenile behaviors like playfulness into adulthood.

Neither of these reasons would explain why our adult chimpanzees were shoving babies out of the way to play with each other that summer. Instead of asking why adults would play, we had to ask what might, in other circumstances, stop them from playing. And for this, we had to go back to the basics of primatology and consider the effects of food on behavior.

The summer of 2017 was notable because there was an unusually high seasonal peak of a lipstick-red fruit called Uvariopsis, a favorite and calorie-rich chimpanzee food. During the months when these fruits are ripe and plentiful, chimpanzees spend more time hanging out together in larger groups.

This sort of energy surplus has been linked to rigorous activities, such as hunting among monkeys. We wondered whether fruit abundance might be linked to social play as well. Perhaps adult play is constrained because grown chimpanzees just don't usually have the extra time and energy to devote to it.

When life gets in the way of play

To test this idea, we turned to the long-term records of the Kibale Chimpanzee Project, extracting nearly 4,000 observations of adult play over 10 years.

Whether tussling with a young chimpanzee or playing chase with another adult, the frequency of adult play was strongly correlated with the amount of ripe fruit in the diet in any given month. When the forest was full of high-quality food, adult chimpanzees played a lot.

But when their prized fruits dwindled, their playful sides all but disappeared – that is, except for mothers.

A surprising sex difference

Among chimpanzees, males are much more social than females. Males invest a lot of time developing friendships, and, in turn, they reap the rewards of those bonds: higher dominance rank and more sex. For females, the high energetic costs of pregnancy and lactation mean socializing comes at the cost of sharing food that they need for themselves and their offspring.

We expected that play, as a social behavior, would follow other social patterns, with males playing more and being able to afford to play even when food abundance was low. To our surprise, we found the opposite. Females played more, especially during months with less fruit – because mothers kept playing with their babies even when all other chimpanzees had stopped.

A hidden cost of motherhood

Chimpanzees live in multimale, multifemale societies that exhibit what researchers call fission-fusion. In other words, the whole social group is rarely, if ever, all together. Instead, chimpanzees break up into temporary subgroups called parties that individuals move among throughout the day.

When food is scarce, parties tend to be smaller, and mothers are often alone with just their young. This strategy reduces feeding competition with group mates. But it also leaves mothers as the only social partners for their offspring. Mothers' time and energy that might be devoted toward other daily tasks, such as feeding and rest, go toward play instead.

Not only did our study reveal this previously unknown cost of motherhood, but it also highlighted how important play must be for these young chimpanzees that their mothers accept this cost.

You might be curious about how chimpanzee fathers fit in here. Chimpanzees mate promiscuously, so males do not know which offspring are theirs. Mothers are left to bear the costs of parenthood on their own.

An ape connection

Child development researchers know that play, and especially play with parents, is critically important for human social development. In fact, caregivers of young children might be reading this in between bouts of play with their little ones right now.

Since chimpanzees are one of our closest living relatives, these kinds of behavioral similarities between our species are not uncommon.

But not all primate parents reckon with costly play. In fact, there are almost no records of monkey mothers playing with their babies at all. Most other primate species, such as baboons and capuchins, don't go their separate ways during the day, so babies can play with each other and moms can catch a break.

Whether maternal play is a product of fission-fusion grouping or the developmental needs of offspring still needs to be tested directly. But the responsibility to play with your little ones certainly resonates with many human parents who experienced a sudden shift to become their children's main play partners when COVID-19 interrupted normal activities.

So on this Mother's Day, consider raising a glass to also celebrate these amazing – and tired – chimpanzee moms.

Zarin Machanda, Assistant Professor of Anthropology and Biology, Tufts University and Kris Sabbi, Fellow in Human Evolutionary Biology, Harvard University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

H. Colleen Sinclair, Louisiana State University

Conspiracy theories are everywhere, and they can involve just about anything.

People believe false conspiracy theories for a wide range of reasons – including the fact that there are real conspiracies, like efforts by the Sackler family to profit by concealing the addictiveness of oxycontin at the cost of countless American lives.

The extreme consequences of unfounded conspiratorial beliefs could be seen on the staircases of the U.S. Capitol on Jan. 6, 2021, and in the self-immolation of a protestor outside the courthouse holding the latest Trump trial.

But if hidden forces really are at work in the world, how is someone to know what's really going on?

That's where my research comes in; I'm a social psychologist who studies misleading narratives. Here are some ways to vet a claim you've seen or heard.

Step 1: Seek out the evidence

Real conspiracies have been confirmed because there was evidence. For instance, in the allegations dating back to the 1990s that tobacco companies knew cigarettes were dangerous and kept that information secret to make money, scientific studies showed problematic links between tobacco and cancer. Court cases unearthed corporate documents with internal memos showing what executives knew and when. Investigative journalists revealed efforts to hide that information. Doctors explained the effects on their patients. Internal whistleblowers sounded the alarm.

But unfounded conspiracy theories reveal their lack of evidence and substitute instead several elements that should be red flags for skeptics:

• Dismissing traditional sources of evidence, claiming they are in on the plot.

• Claiming that missing information is because someone is hiding it, even though it's common that not all facts are known completely for some time after an event.

• Attacking apparent inconsistencies as evidence of lies.

• Overinterpreting ambiguity as evidence: A flying object may be unidentified – but that's different from identifying it as an alien spaceship.

• Using anecdotes – especially vaguely attributed ones – in place of evidence, such as “people are saying” such-and-such or “my cousin's friend experienced” something.

• Attributing knowledge to secret messages that only a select few can grasp – rather than evidence that's plain and clear to all.

Step 2: Test the allegation

Often, a conspiracy theorist presents only evidence that confirms their idea. Rarely do they put their idea to the tests of logic, reasoning and critical thinking.

While they may say they do research, they typically do not apply the scientific method. Specifically, they don't actually try to prove themselves wrong.

So a skeptic can follow the method scientists use when they do research: Think about what evidence would contradict the explanation – and then go looking for that evidence.

Sometimes that effort will yield confirmation that the explanation is correct. And sometimes not. Like a scientist, ask yourself: What would it take for you to believe your perception was wrong?

Step 3: Watch out for tangled webs

When theories claim large groups of people are perpetrating wide-ranging activities over a long period of time, that's another red flag.

Confirmed conspiracies typically involve small, isolated groups, like the top echelon of a company or a single terrorist cell. Even the alliance among tobacco companies to hide their products' danger was confined to those at the top, who made decisions and enlisted paid scientists and ad agencies to spread their messages.

False conspiracies tend to implicate wide swaths of people, such as world leaders, mainstream media outlets, the global scientific community, the Hollywood entertainment industry and interconnected government agencies.

The online manifesto of Max Azzarello – the man who self-immolated on the steps of a New York courthouse in April 2024– railed against a conspiracy allegedly including every president since Bill Clinton, sex offender Jeffrey Epstein, even the writers of “The Simpsons.”

Remember that the more people who supposedly know a secret, the harder it is to keep.

Step 4: Look for a motive

Confirmed conspiracies tell stories about why a group of people acted as they did and what they hoped to gain. Dubious conspiracies involve a lot of accusations or just questions without examining what real benefit the conspiracy nets the conspirators, especially when factoring in the costs.

For instance, what purpose would NASA have to lie about the existence of Finland?

Be particularly suspicious when conspiracies allege an “agenda” being perpetrated by an entire sociodemographic, which is often a marginalized group, such as a “gay agenda” or “Muslim agenda.”

Also look to see whether those spreading the conspiracy theories have something to gain. For example, scholarly research has identified the 12 people who are the primary sources of false claims about vaccinations. The researchers also found that those people profit from making those claims.

Step 5: Seek the source of the allegations

If you can't figure out who is at the root of a conspiracy allegation and thus how they came to know what they claim, that is another red flag. Some people say they have to remain anonymous because the conspiracists will take revenge for revealing information. But even so, a conspiracy can usually be tracked back to its source – maybe a social media account, even an anonymous one.

Over time, anonymous sources either come forward or are revealed. For instance, years after the Watergate scandal took down Richard Nixon's presidency, a key inside source known as “Deep Throat” was revealed to be Mark Felt, who had been a high-level FBI official in the early 1970s.

Even the notorious “Q” at the heart of the QAnon conspiracy cult has been identified, and not by government investigators chasing leaks of national secrets. Surprise! Q is not the high-level official some people believed.

Reliable sources are transparent.

Step 6: Beware the supernatural

Some conspiracy theories – though none that have been proven – involve paranormal, alien, demonic or other supernatural forces. People alive in the 1980s and 1990s might remember the public fear that satanic cults were abusing and sacrificing children. That idea never disappeared entirely.

And around the same time, perhaps inspired by the TV series “V,” some Americans began to believe in lizard people. It may seem harmless to keep hoping for evidence of Bigfoot, but the person who detonated a bomb in downtown Nashville on Dec. 25, 2020, apparently believed lizard people ran the Earth.

The closer the conspiracy is to science fiction, the closer it is to just being fiction.

Step 7: Look for other warning signs

There are other red flags too, like the use of prejudicial tropes about the group allegedly behind the conspiracy, particularly antisemitic allegations.

But rather than doing the work to really examine their conspiratorial beliefs, believers often choose to write off the skeptics as fools or as also being in on it – whatever “it” may be.

Ultimately, that's part of the allure of conspiracy theories. It is easier to dismiss criticism than to admit you might be wrong.

H. Colleen Sinclair, Associate Research Professor of Social Psychology, Louisiana State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Ron Barrett, Macalester College

The last pandemic was bad, but COVID-19 is only one of many infectious diseases that emerged since the turn of this century.

Since 2000, the world has experienced 15 novel Ebola epidemics, the global spread of a 1918-like influenza strain and major outbreaks of three new and unusually deadly coronavirus infections: SARS, MERS and, of course, COVID-19. Every year, researchers discover two or three entirely new pathogens: the viruses, bacteria and microparasites that sicken and kill people.

While some of these discoveries reflect better detection methods, genetic studies confirm that most of these pathogens are indeed new to the human species. Even more troubling, these diseases are appearing at an increasing rate.

Despite the novelty of these particular infections, the primary factors that led to their emergence are quite ancient. Working in the field of anthropology, I have found that these are primarily human factors: the ways we feed ourselves, the ways we live together, and the ways we treat one another. In a forthcoming book, “Emerging Infections: Three Epidemiological Transitions from Prehistory to the Present,” my colleagues and I examine how these same elements have influenced disease dynamics for thousands of years. Twenty-first century technologies have served only to magnify ancient challenges.

Neolithic infections

The first major wave of newly emerging infections occurred with the start of the Neolithic revolution about 12,000 years ago, when people began shifting from foraging to farming as their primary means of subsistence.

Before then, human infections tended to be mild and chronic in nature, manageable burdens of long-term parasites that people carried around from place to place. But full-time agrarian living brought the kinds of acute and virulent infections that we are familiar with today. This global shift was humanity's first epidemiological transition.

Farming itself was not the cause. Rather, it was the major lifestyle changes associated with this new enterprise. Agriculture supplied people with high-calorie grains, but often did so at the expense of dietary diversity, resulting in compromised immunity from nutritional deficiencies.

The human population increased dramatically, and so did the number of large and densely settled communities that could sustain the transmission of deadlier pathogens.

Our ancient ancestors domesticated animals for food and labor, and their proximity to one another created opportunities for livestock diseases to evolve into human diseases.

Finally, the social hierarchies of newly agrarian societies led to disparities in the distribution of essential resources for healthy living.

These challenges of subsistence, settlement and social organization were the root causes of humanity's first major disease transition.

Declining infections

For a dozen millennia, these patterns spread across the world like a plague of plagues. They persisted until the 19th and 20th centuries, when life expectancy rose with the precipitous decline of infectious diseases in high- and middle-income countries.

Remarkably, the greatest proportion of this decline occurred before the discovery of effective antibiotics and most of the vaccines we use today. Health improvements were mainly due to nonmedicinal factors such as better farming and food distribution methods, major sanitation projects and housing reforms in poor urban areas.

These were significant reversals in the same ancient categories – subsistence, settlement and social organization – that led to the rise of infectious diseases in the first place. They resulted in humanity's second epidemiological transition, a significant but only partial reversal of the changes that first began in the Neolithic period.

This second pattern was not a panacea. Despite overall health improvements, chronic noninfectious conditions such as heart disease and cancer rose to become the primary causes of human mortality.

Most low-income countries experienced a later version of this transition after World War II, but their health gains from declining infections were significantly less than those of their wealthier counterparts. At the same time, their losses to noninfectious diseases rose at comparable rates. These conflicting trends have led to a “worst-of-all-worlds” scenario with respect to the health of poor societies.

It is also worth noting that the declining infections in low-income societies have depended more on affordable antimicrobial drugs. Given the emergence of drug-resistant pathogens, these medicinal buffers are proving to be little more than short-term solutions for the health consequences of poverty.

With the ability of pathogens to move freely across borders and boundaries, these consequences can quickly become everyone's problems.

Converging infections

In recent decades, humanity's interconnections have reached the point that nearly everyone now lives within a single global disease environment. Borders and boundaries no longer constrain the spread of distant outbreaks. The COVID-19 pandemic dramatically illustrated this new reality, when the SARS-CoV-2 virus spread around the world in only a few weeks.

The COVID-19 pandemic also highlighted the ways that infectious and noninfectious diseases can interact synergistically with one another to produce even worse outcomes than the simple sum of each disease. This is starkly illustrated by the majority of COVID-19 deaths, which occurred among people with chronic heart, lung and metabolic conditions that are common to a growing proportion of older people in populations both wealthy and poor.

When combined, these challenges have set the stage for the converging disease patterns visible today. This is the third epidemiological transition: the rise of new, virulent and drug-resistant infections occurring in a rapidly aging and highly interconnected world.

Unfortunately, the present pattern entails increasing outbreaks of new and deadly infections. The root causes of these outbreaks are in areas such as commercial agricultural practices, the urbanization of human populations and the challenges of poverty in the face of economic growth.

Despite the magnitude of these determinants, they are essentially the same issues of subsistence, settlement and social organization from 12,000 years ago. Addressing these recurring issues will do more than prepare the world for future pandemics; it will help to prevent them from happening in the first place.

Ron Barrett, Associate Professor of Anthropology, Macalester College

This article is republished from The Conversation under a Creative Commons license. Read the original article.