Monday, September 22, 2025

Research shows there are no easy fixes to political hatred

Study finds that interventions to reduce partisan animosity have fleeting effects.

Dartmouth College

Tune into American politics today, and you'll hear something far more sinister than simple disagreement. The language has escalated: political parties trash talk each other—blaming rival parties for policy failures or even for causing incidents with national implications.

And reducing polarization and "partisan animosity"—the distrust and hatred of the other party—is remarkably difficult, according to a new study published in the Proceedings of the National Academy of Sciences evaluating past attempts.

The research was led by the Polarization Research Lab, a nonpartisan team of political scientists from Dartmouth and the University of Pennsylvania.

"As long as political and media systems reward outrage with votes and viewership—stoking division—any individual-level effort to depolarize is up against a powerful, unending tide," says senior author Sean Westwood, an associate professor of government at Dartmouth and director of the Lab. "This isn't a problem that can be fixed at the grassroots level alone."

To determine if efforts to reduce partisan animosity have a lasting effect, the researchers conducted a massive meta-analysis of 25 previous studies, encompassing 77 different approaches. These "treatments" included everything from correcting misperceptions about the rival party to encouraging conversations with opponents and calls for civility from party leaders.

The study shows that such superficial interventions are largely ineffective.

On average, treatments improved a person's feelings towards the other political party by a mere 5.3%. The authors note this small gain is dwarfed by the 7% increase in partisan animosity observed between the 2016 and 2020 U.S. elections alone.

The results are not only modest, but fleeting. The researchers found that 75% of the initial reduction in hostility disappears after just one week. Within two weeks, the effects are almost completely gone.

The team also conducted two new large-scale experiments to see if combining or repeating interventions could work better.In one experiment with 3,500 respondents, they tested if "stacking treatments"—by exposing people to multiple interventions at once—would amplify the positive effect.

In another experiment with over 5,000 respondents, they evaluated if providing a "booster shot"—a repeated treatment over time—would make the effects last longer.

The results were clear: neither stacking treatments nor administering them repeatedly produced significantly larger or more durable results. In essence, flooding the airwaves with public service announcements to counter political hatred is not an effective strategy.

"To achieve lasting depolarization in the U.S., a fundamental shift in society is needed," says Westwood. "From the top down, we must address the behavior of political elites and the structural incentives that fuel conflict, and from the bottom up, we need a citizenry with the civic skills to engage constructively across differences."

The co-authors report that while interventions built on genuine dialogue are difficult to scale, they remain the single most effective tool for reducing polarization and require long-term investment.

"Principles of civil discourse and respectful dialogue need to be embedded into the education system in the U.S.," says Westwood. "The future of our democracy depends on it."

Westwood says, "Without more systematic changes, America's divisions will only continue to deepen."

Longtime collaborators Derek Holliday at The George Washington University and Yphtach Lelkes at the University of Pennsylvania also contributed to the study.

Westwood is available for comment at: sean.j.westwood@dartmouth.edu.

###

Journal

Proceedings of the National Academy of Sciences

Article Title

Why Depolarization is Hard: Evaluating Attempts to Decrease Partisan Animosity in America

Article Publication Date

22-Sep-2025

A recipe from two eras: How conifers ward off their enemies

Today's conifers contain a mixture of ancient and recent defense substances in their resin, which may be key to combating bark beetles

Max Planck Institute for Chemical Ecology

image:
Andrew O’Donnell in front of a gel imaging system. The gel image visualizes the purified ancestral terpene synthase enzymes examined in the study.
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Credit: Angela Overmeyer, Max Planck Institute for Chemical Ecology

To the point:

Conifers use resin to protect themselves against pests. This resin contains diterpenes, which are defensive substances.
Some of these diterpenes originated over 300 million years ago, before conifers evolved. Other diterpenes developed independently in different conifer species much later, presumably to protect against bark beetles.
This repeated evolution was only possible because enzymes that produce diterpenes had previously undergone changes that unlocked evolutionary pathways towards certain substances. This is based on a mechanism called “epistasis”, which allows new traits to evolve once preparatory changes have already occurred in some cases.
The findings provide insight into the evolutionary mechanisms of conifer defenses and could help us better understand and utilize natural plant protection.

Conifers, such as pines, spruces, and firs, produce sticky resins that protect the trees from insects and pathogens. Important components of this resin are diterpenes, special natural substances that repel bark beetles and fungi. The enzymes that produce these compounds are called diterpene synthases.

A research team at the Max Planck Institute for Chemical Ecology in Jena, Germany, and Iowa State University in Ames, Iowa, USA, wanted to find out whether these enzymes originated once in the distant past or evolved independently in different conifers more recently. "Diterpene synthases are exciting enzymes because even minor structural changes cause them to produce different chemical products. They are therefore ideal for investigating how plants came to produce such an enormous variety of defense substances over the course of evolution," said Andrew O'Donnell, the study's first author from the Department of Biochemistry, explaining the research's starting point.

A journey into the evolutionary past of enzymes

To unravel the evolutionary history of these enzymes, the team performed genetic analyses to reconstruct probable ancestral diterpene synthases and study them in the laboratory. The scientists modified these reconstructed enzymes to observe how their products changed. "To determine an enzyme's products, we transferred its genes into bacteria. The bacteria then produced the enzyme for us. We isolated the enzyme, added suitable starting materials, and analyzed the resulting products in detail using modern analytical methods," explained Axel Schmidt, head of the Conifer Defense Project Group.

In order to determine the age of certain ancestral enzymes, the researchers had to take into account the sequences of numerous diterpene synthases as well as the evolutionary relationships among conifer species. The result: Some of the diterpenes found in today's conifer resin originated 300 million years ago, long before pine, spruce, and fir trees existed in their current forms. Other important diterpenes, however, developed more recently and independently in several different tree species.

Why evolution sometimes takes a very long time

This raised the question of why some of these compounds took so long to develop – yet still led to similar results in different tree species. A genetic mechanism called epistasis played a central role in this process. New traits often emerge only if other changes occurred beforehand. "The potential for plants to develop certain substances increased slowly over millions of years and then dramatically after conifers separated from other plants. This could explain why some plant groups develop the same characteristics repeatedly," says Andrew O'Donnell.

Protection against bark beetles

Today, conifer resin is a mixture of ancient and more recent diterpenes. These more recent defensive substances may have developed when bark beetles already existed, as supported by fossil findings. Despite following different evolutionary paths, pine, spruce, and fir trees probably developed identical diterpenes independently as a defense against these pests.

This unique blend of ancient and more recent defensive substances may be crucial to how well trees fend off current pests, such as bark beetles. "A tree's ability to adapt quickly to new challenges, such as bark beetle attacks, depends on the changes that have already occurred in its metabolism over the course of evolution. This prehistory determines which new characteristics can develop — and thus, how well the plant adapts," explains Jonathan Gershenzon, head of the Department of Biochemistry.

The researchers now want to investigate how the evolution of diterpenes and diterpene synthases has influenced the trees' ability to defend themselves today against both bark beetles and their associated fungal species. A mixture of substances is likely needed to most effectively defend against the dual threat of beetles and fungi.

Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2510962122

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Favorable epistasis in ancestral diterpene synthases promoted convergent evolution of a resin acid precursor in conifers

Article Publication Date

26-Sep-2025

Want to save an endangered species? Start with the right DNA blueprint

New research led by USC Dornsife shows that when genomics studies rely on stand-in reference DNA from similar but different species, findings from genetic data can be distorted by up to 60% — putting vulnerable species at greater risk.

University of Southern California

Key points:

Since few species have their own sequenced genome, scientists often use the DNA of a related species as a stand-in — a shortcut that can distort research findings.
A new study published in Cell shows that, in animals such as gray foxes, using something other than a species-specific genome can miss up to a third of genetic variations — a problem that threatens nearly all species without their own sequenced genome.
Such errors could mislead conservation efforts, diverting resources to the wrong places and leaving truly at-risk species unprotected.

When scientists want to trace how a species has changed over time — and predict its prospects for survival — they turn to DNA. But what if the genetic map guiding them belongs to the wrong animal?

A new study led by researchers at the USC Dornsife College of Letters, Arts and Sciences shows that using the wrong “reference genome” — the master sequence scientists rely on to compare DNA — can significantly distort the picture. For the gray fox, one of North America’s most common wild canids, mapping against a dog or Arctic fox genome, instead of its own, made populations look smaller, less diverse and even in decline when they were actually stable or growing.

“It turns out the reference you use really changes the story you tell about a species,” said Jazlyn Mooney, Gabilan Assistant Professor of Quantitative and Computational Biology at USC Dornsife and corresponding author of the study published in Cell. “If you use the wrong reference, you can end up with misleading answers about a species’ history or health, and even its chances of long-term survival.”

Scientists put a reference genome to the test

Every genetic study needs a starting point: a reference genome, usually built by sequencing the DNA of one individual of a species. When scientists study additional individuals, they align the new DNA against that reference for comparison.

But many species, especially those less studied, lack their own reference. In these cases, researchers turn to the next best option — a close relative. For decades, the domestic dog’s genome has stood in for foxes, wolves and wild dogs.

Mooney and her colleagues wondered just how much that choice matters. Would using a genetically distant blueprint simply blur the details, or could it actually rewrite the story?

The team re-analyzed DNA from 12 gray foxes — six from eastern North America and six from the West — comparing how their genomes aligned to three different references: the gray fox itself, the domestic dog and the Arctic fox.

They asked:

How much genetic variation appears?
What does the data reveal about past population sizes?
Are current populations growing or shrinking?
Which genes seem to be under natural selection, hinting at adaptation?

The answers depended heavily on which genome served as the map.

This is the kind of thing that could change conservation decisions.

With the gray fox’s own genome, researchers detected 26%–32% more genetic differences among individuals and about a third more rare variants (the subtle DNA changes that reveal how populations have been evolving recently).

Estimates of population size were also 30%–60% higher. In the western United States, for instance, the gray fox genome showed stability and growth, while the dog and Arctic fox genomes suggested decline.

The wrong reference also threw off measures of how DNA shuffles during reproduction. With the dog or Arctic fox genomes, the numbers sometimes doubled or even tripled compared with the gray fox genome, especially near the ends of chromosomes.

“This is the kind of thing that could change conservation decisions,” Mooney said. “If you think a population is shrinking when it’s not, or vice versa, you might end up protecting the wrong group or missing an opportunity to safeguard genetic diversity.”

The study also showed that using the wrong reference could create misleading signs of natural selection. The dog and Arctic fox genomes identified twice as many potential DNA “hot spots”— regions that looked like they might be adaptive — compared with the gray fox genome. Many of these signals were false alarms, caused by the mismatch between species.

Why the right reference genome matters for conservation — and people

The study’s implications go well beyond foxes. Conservation biologists use genetic data to decide which populations to protect, how to design breeding programs and whether endangered species are at risk of inbreeding. If the genetic picture is distorted, those decisions may rest on shaky ground.

That could affect high-profile species such as the Ethiopian wolf, the African wild dog or even the tiny Channel Island foxes off Southern California’s coast. For animals already on the edge, a flawed map could mean misjudging their vulnerability.

“Maintaining the world’s biodiversity isn’t just about saving animals for their own sake,” Mooney said. “Biodiversity supports clean water, food security and climate stability. If conservation plans are based on incomplete or biased genetic information, we risk mismanaging species and weakening the natural systems people depend on.”

These findings echo a lesson from human genetics: For years, the human reference genome drew mostly from just a few people, limiting research across populations. More recent efforts are building references that better reflect global diversity.

Scientists call for better genomic maps

The researchers argue that the solution is to invest in building species-specific reference genomes. Assembling a high-quality genome sequence is expensive, and nearly 99% of species still lack one, but the payoff could be crucial.

For species without their own reference, Mooney and her team point to new computational methods and building high quality genomes that capture more of a species’ diversity — as ways to reduce bias.

“We’re not saying every species will be as impacted as gray foxes,” Mooney said. “But our study shows the risks are real, and can lead you astray.”

The gray fox study stands as both a warning and a call to action: choosing the wrong reference doesn’t just blur the details — it can redraw a species’ past and future.

About the study

In addition to corresponding author Mooney, the research team includes first author and former USC Dornsife postdoctoral fellow Maria Akopyan, now at the University of California, Riverside; USC undergraduate Matthew Genchev; and Assistant Professor Ellie Armstrong of UC Riverside.

Journal

Cell

DOI

10.1016/j.cell.2025.08.034

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

Reference genome choice compromises population genetic analyses

Article Publication Date

22-Sep-2025

COI Statement

N/A

Study shows UV light can disable airborne allergens within 30 minutes

The findings could lead to new ways to prevent allergies at home, school and in the workplace

University of Colorado at Boulder

UV 222 light — image:
UV222 lights hang on the ceiling of the Aerobiology and Disinfection Laboratory at CU Boulder.
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Credit: Patrick Campbell/CU Boulder

Cats. Dust mites. Mold. Trees.

For people with allergies, even a brief whiff of the airborne allergens these organisms produce can lead to swollen eyes, itchy skin and impaired breathing.

Such allergens can persist indoors for months after the original source is gone, and repeated exposure can exacerbate, and even lead to, asthma.

What if you could just flip a switch and disable them? You can, according to new University of Colorado Boulder research.

“We have found that we can use a passive, generally safe ultraviolet light treatment to quickly inactivate airborne allergens,” said study author Tess Eidem, a senior research associate in the Department of Civil, Environmental and Architectural Engineering.

“We believe this could be another tool for helping people fight allergens in their home, schools or other places where allergens accumulate indoors.”

The findings were published in August in the journal ACS ES&T Air.

Why you can’t kill an allergen

Walk into a room with a cat and, if you sneeze, it’s not actually the cat you are reacting to. It’s likely airborne flecks of a protein called Fel d1 produced in their saliva. The protein spreads when they lick themselves and ends up in microscopic flakes of dead skin floating in the air, a.k.a. dander. When we inhale these particles, our immune system produces antibodies that bind to the protein’s unique 3D structure, kicking off an allergic reaction.

Dogs, mice, dust mites, mold and plants all emit their own unique proteins, with their own unique structure. Unlike bacteria and viruses, these allergens can’t be killed because they were never alive.

“After those dust mites are long gone, the allergen is still there,” said Eidem. “That’s why, if you shake out a rug, you can have a reaction years later.”

Standard methods of reducing allergens — like vacuuming, washing walls, using an air filter and regularly bathing pets — can work OK but are hard to maintain long-term studies show.

Eidem and co-authors Mark Hernandez, a professor of Civil, Environmental and Architectural Engineering, and Kristin Rugh, a microbiologist in the lab, sought a simpler way.

Instead of eliminating the proteins that cause allergies, they sought to change their structure — much like unfolding an origami animal — so the immune system wouldn’t recognize them.

“If your immune system is used to a swan and you unfold the protein so it no longer looks like a swan, you won’t mount an allergic response,” explained Eidem.

UV light, their study suggests, can do that.

Let there be light

Previous research has shown that UV light can kill airborne microorganisms, including the virus that causes COVID-19.

It’s already used widely to disinfect equipment in hospitals, airports and elsewhere, but the bandwidth is typically so strong (a wavelength of 254 nanometers) that users must wear protective equipment to prevent damage to skin and eyes.

Eidem used 222-nanometer-wavelength lights, a less-intense alternative considered safe for occupied spaces because it doesn’t penetrate deep into cells. (It does not come entirely without risks, including ozone production, she notes, so exposure should be limited.)

The team pumped microscopic aerosolized allergens from mites, pet dander, mold and pollen into an unoccupied and sealed 350-cubic-foot chamber. Then they switched on four lunchbox-sized UV222 lamps on the ceiling and floor.

When they sampled the air at 10-minute intervals and compared it to untreated, allergen-filled air via laboratory tests, they saw significant differences. In the treated samples, immunorecognition was reduced, meaning the antibodies no longer recognized many of the proteins and stuck to them.

After just 30 minutes, airborne allergen levels effectively decreased by about 20% to 25% on average, the study showed.

“Those are pretty rapid reductions when you compare them to months and months of cleaning, ripping up carpet, and bathing your cat,” said Eidem.

A portable allergy buster?

UV222 lights are already commercially available, mostly for industrial antimicrobial uses.

But Eidem envisions a day when companies could engineer portable versions for people to switch on when they visit a friend with a pet or clean out a dusty basement.

UV222 systems could also potentially protect workers frequently exposed to allergens, such as those who work around live animals or in cannabis grow houses where, her own research shows, allergic reactions can be deadly.

One-in-three adults and children in the United States have allergies, according to the Centers for Disease Control. Eidem hopes her research, and more to come, can provide them with some relief — or even save lives.

“Asthma attacks kill about 10 people every day in the United States, and they are often triggered by airborne allergies,” she said. “Trying to develop new ways to prevent that exposure is really important.”

Tess Eidem holds up a jar of fungus used to generate allergens for research.

Tess Eidem pumps allergens into a chamber to study the impact of UV light on them.

Credit

Patrick Campbell/CU Boulder

DOI

10.1021/acsestair.5c00080

Method of Research

Experimental study

Subject of Research

Cells

Article Title

Far UV Exposure (UV222) Decreases Immune-Based Recognition of Common Airborne Allergens

Indoor surfaces act as massive sponges for harmful chemicals, UC Irvine-led study shows

Permeable materials in homes can retain volatile organic compounds for up to a year

University of California - Irvine

Irvine, Calif., Sept. 22, 2025 — Indoor surfaces have an unexpectedly strong ability to absorb and hold harmful chemical compounds that can threaten human health for as long as a year, according to air chemistry researchers at the University of California, Irvine.

In a paper published today in Proceedings of the National Academy of Sciences, the UC Irvine scientists quantify how various indoor surfaces absorb volatile organic compounds, which can result in unhealthy conditions for people and animals when inhaled or absorbed through skin contact.

The sources of VOCs are many, such as cooking, spray cleaning, personal care and other consumer products. Additional significant contributors include tobacco smoke and, increasingly, air pollution caused by wildfires. The researchers note that health risks come from inhaling compounds when they “off gas” from surfaces and through dermal uptake when contaminated surfaces are touched.

In the spring of 2022, co-author Jonathan Abbatt, professor of chemistry at the University of Toronto, led the Chemical Assessment of Surfaces and Air study, which utilized simulation chambers in the National Institute of Standards and Technology’s Net-Zero Energy Residential Test Facility. Contaminants were injected into a structure mimicking a home environment, with typical building materials. The research team used mass spectrometry instruments to track the movement and persistence of VOCs in the controlled indoor environment.

“Scientists in the air chemistry research community have known for a long time that many indoor contaminants can be absorbed by indoor surfaces, but the size of indoor surface reservoirs inside homes and buildings had not been established,” said Manabu Shiraiwa, UC Irvine professor of chemistry, who was responsible for modeling observations and is a corresponding author on the PNAS paper. “Our modeling found that surfaces inside homes have a much greater size to absorb and hold chemicals than previously realized. We can think of these surfaces as massive chemical sponges that soak up VOCs.”

Before this study, thin organic films with nanometer thickness were thought to be main surface reservoirs. However, this work proves that permeable and porous materials such as painted surfaces, cement and wood are likely the major surface reservoirs in a home.

“This discovery has significant implications for human health,” Shiraiwa said. “It means people can be exposed to harmful chemicals long after their initial introduction into indoor spaces, and compounds can later be released back into the air or transferred to humans through direct contact with contaminated surfaces.”

He added, “This result significantly impacts our understanding of VOC fate and human exposure in indoor environments. With such a large partitioning capacity, organic contaminants will have much longer indoor residence times than previously predicted.”

The research explains why certain odors and contaminants persist indoors even after their sources are removed. For example, it provides scientific evidence for why tobacco smoke odors linger in rooms long after smoking has stopped: The residual compounds, known as “thirdhand smoke,” slowly partition back into the air from surface reservoirs.

The findings suggest that regular ventilation alone may be insufficient to remove many indoor contaminants. Physical cleaning activities such as vacuuming, mopping and dusting are necessary to effectively remove compounds with high partition coefficients from surface reservoirs.

Joining Shiraiwa and Abbatt in this study were Pascale Lakey, project scientist in chemistry at UC Irvine; Jie Yu and Xing Wang at the University of Toronto; Jenna Ditto at Washington University in St. Louis, Missouri; Han Huynh and Marina Vance at the University of Colorado Boulder; Michael Link, Dustin Poppendieck and Stephen Zimmerman at the National Institute of Standards and Technology; and Delphine Farmer at Colorado State University.

The research was supported by funding from the Alfred P. Sloan Foundation.

About the University of California, Irvine: Founded in 1965, UC Irvine is a member of the prestigious Association of American Universities and is ranked among the nation’s top 10 public universities by U.S. News & World Report. The campus has produced five Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UC Irvine has more than 36,000 students and offers 224 degree programs. It’s located in one of the world’s safest and most economically vibrant communities and is Orange County’s second-largest employer, contributing $7 billion annually to the local economy and $8 billion statewide. For more on UC Irvine, visit www.uci.edu.

Media access: Radio programs/stations may, for a fee, use an on-campus studio with a Comrex IP audio codec to interview UC Irvine faculty and experts, subject to availability and university approval. For more UC Irvine news, visit news.uci.edu. Additional resources for journalists may be found at https://news.uci.edu/media-resources.

Journal

Proceedings of the National Academy of Sciences

Article Title

VOC injection into a house reveals large surface reservoir sizes in an indoor environment

Article Publication Date

22-Sep-2025