Out of the frying pan: Coyotes, bobcats move into human-inhabited areas to avoid apex predators — only to be killed by people

Peer-Reviewed Publication

UNIVERSITY OF WASHINGTON

 

IMAGE: THIS IMAGE SHOWS A BOBCAT BEING RELEASED BACK INTO THE WILD IN FEBRUARY 2020 AFTER BEING FITTED WITH A GPS COLLAR AS PART OF THE WASHINGTON PREDATOR-PREY PROJECT. view more 

CREDIT: ZACHARY WARDLE

Link to Google Drive folder containing images:

https://drive.google.com/drive/folders/1Wv5Va5E0Pti0kLRogMUdoSnCEIaWlEFy?usp=sharing

Since their protection under the Endangered Species Act, wolf populations have been making a comeback in the continental United States. Conservationists have argued that the presence of wolves and other apex predators, so named because they have no known predators aside from people, can help keep smaller predator species in check.

New research shows that in Washington state, the presence of two apex predators — wolves and cougars — does indeed help keep populations of two smaller predators in check. But by and large the apex predators were not killing and eating the smaller predators, known as mesopredators. Instead, they drove the two mesopredator species — bobcats and coyotes — into areas with higher levels of human activity. And people were finishing the job.

The study — published May 18 in the journal Science by researchers at the University of Washington, the Washington Department of Fish and Wildlife and the Spokane Tribe of Indians — reports that bobcats and coyotes were more than three times likely to die from human activity, like hunting or trapping, than from the claws and jaws of cougars and wolves.

The findings illustrate how humankind’s growing footprint is changing interactions among other species.

“When cougars and wolves moved into an area, coyotes and bobcats employed a specific strategy to avoid apex predators by moving into more human-impacted regions,” said lead author Laura Prugh, a wildlife ecologist and UW associate professor in the School of Environmental & Forest Sciences. “That indicated to us that coyotes and bobcats likely perceived these large carnivores as a greater threat to them than people. But when we looked at causes of mortality for the mesopredators, humans were by far the largest cause of death.”

For the study, researchers used GPS collars to track the activity of 22 wolves (Canis lupus), 60 cougars (Puma concolor), 35 coyotes (Canis latrans) and 37 bobcats (Lynx rufus) across two study areas in north central and northeastern Washington from winter 2017 to summer 2022 as part of the Washington Predator-Prey Project. The study areas — which included portions of Okanagan, Stevens, Spokane, Pend Oreille and Lincoln counties — consisted of national forests; recreational areas for camping, hunting and fishing; and lands dedicated to agriculture, timber harvesting, ranching and residential use.

Tracking data indicated that, when wolves or cougars moved into their region, bobcats and coyotes would shift their movements accordingly.

“Coyotes and bobcats started using areas that had twice as much human influence compared to where they were before the large carnivores moved in,” said Prugh.

Researchers also attempted to determine the cause of death for any tracked animals that died during the study period. They discovered that areas with high human activity were far more deadly to mesopredators than those without a large human presence.

More than half of the 24 coyotes that died over the course of the study were killed by people. Some were shot after preying on livestock. Humans also killed half of the 22 bobcats that died during the study, including several that were attacking chickens.

In general, humans killed between three and four times more mesopredators in this study than wolves or cougars, both of which typically avoid areas with high levels of human activity.

In the short term, human activity poses little threat to the overall populations of bobcats and coyotes, which are two of the most widespread mesopredators in North America. Neither are endangered, and coyotes in particular are highly adaptable to the presence of people.

But not all mesopredator species are as resilient in human areas as coyotes and bobcats, said Prugh. Others reproduce more slowly or may be vulnerable in multiple ways to human activity. Rodent poisons used to keep away pests, for example, can kill fishers, another mesopredator species.

Future studies would need to investigate how mesopredators use space and resources in areas with high human activity, and what the risks of these shifts are to people.

“These are not trivial shifts in territory or space,” said Prugh. “There are real consequences.”

The findings also add a wrinkle to a working theory of wildlife-human interactions called the human shield hypothesis. Under the hypothesis, the presence of predators in a region causes prey species to move to areas with higher human activity. In Yellowstone National Park, for example, elk have at times moved near hiking trails, which wolves and other large carnivores typically avoid.

But the impact of humans in Yellowstone is typically smaller compared to other types of recreational areas or farms, grazing lands and residential developments – leaving some scientists to wonder if humans would be much of a “shield” in those areas.

“In these areas with higher levels of human activity, it was unknown whether a mesopredator would perceive the apex predator or humans as the greater threat,” said Prugh. “Here, we found that bobcats and coyotes perceived their apex predators as the greater threat, but their strategy of avoiding those large carnivores backfired by bringing them into contact with a much more effective predator: us.”

Co-authors are UW postdoctoral researcher Calum Cunningham; former UW researcher Rebecca Windell; Brian Kertson, a biologist with the Washington Department of Fish and Wildlife; Taylor Ganz, a UW doctoral student in environmental and forest sciences; Savanah Walker with the Spokane Tribe of Indians; and Aaron Wirsing, UW professor of environmental and forest sciences. The research was funded by the National Science Foundation, the Washington Department of Fish and Wildlife and the Australia Fulbright Program.

###

For more information, contact Prugh at lprugh@uw.edu.

Grant numbers: DEB-1652420, 16-07846

Reference: Prugh LR, Cunningham CX, Windell RM, Kertson BN, Ganz TR, Walker SL and Wirsing AJ. “Fear of large carnivores amplifies human-caused mortality for mesopredators.” Science 2023. DOI: 10.1126/science.adf2472

A note from Science for journalists: “Advance copies of embargoed papers may be obtained by registered reporters from our press package, SciPak, at https://www.eurekalert.org/press/scipak/. For reporters having difficulties accessing the paper from the press package, please have them contact scipak@aaas.org. After embargo lift, anyone may view a copy of your manuscript at https://www.science.org/journal/science.”

This video shows UW researchers trapping a bobcat in 2020, fitting it with a GPS collar and releasing it as part of the Washington Predator-Prey Project:
https://www.youtube.com/watch?v=fYPCD6yKNHs [Credit: Calum Cunningham]

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JOURNAL

Science

DOI

10.1126/science.adf2472 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Fear of large carnivores amplifies human-caused mortality for mesopredators

ARTICLE PUBLICATION DATE

18-May-2023

This image taken by a game camera at night shows a coyote wearing a GPS collar in September 2018 as part of the Washington Predator-Prey Project.

CREDIT

Savanah Walker

Fear of large predators drives smaller predators into areas they perceive as safer, but where risk is greater

Peer-Reviewed Publication

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)

Medium-sized carnivorous species – mesopredators like coyotes or bobcats – tend to move into human-dominated areas to avoid predation by larger carnivores, a phenomenon also known as the “human shield” effect. However, according to a new study, doing so places these safety-seeking species at considerably greater risk for mortality due to human activities. The findings describe a “paradox of the lethal human shield” for mesopredators, which could become an increasingly important driver of carnivore community dynamics and ecological trophic structures as species restoration and recovery efforts expand the coexistence of large predators and humans in shared landscapes. Although the use of human shields has been linked to increased wildlife survival rates in some instances, it also has the potential to impose increased risk for human-caused mortality through hunting, human-wildlife conflict removals, or vehicular collisions. However, the interacting dangers posed by large carnivores and humans affect the behavior and mortality of smaller predators remains poorly understood. Using data from radio-collared coyotes and bobcats (mesopredators), as well as wolves and cougars (sympatric large carnivores), Laura Prugh and colleagues investigated the movements of these animals in relation to one another and in relation to substantial human activities across northern Washington state. Prugh et al. found that smaller predators tended to move away from the larger predators into areas with greater human influence, suggesting the smaller species perceived humans to be less of a threat than larger carnivores. However, rather than shielding mesopredators and improving their overall survival, the authors discovered that the human-caused mortality rates for mesopredators were more than three times higher than large-carnivore-caused mortality in these areas. Prugh et al. suggest that this scenario could represent an ecological trap. “Despite uncertainty among underlying behavioral and evolutionary processes, the study by Prugh et al. highlights the ecological implications of human influence on relationships among multiple trophic levels,” write Chris Darimont and Ishana Shukla in a related Perspective.

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JOURNAL

Science

DOI

10.1126/science.adf2472 

ARTICLE TITLE

Fear of large carnivores amplifies human-caused mortality for mesopredators

ARTICLE PUBLICATION DATE

19-May-2023

Unmanaged global forests have limited carbon sequestration potential

Peer-Reviewed Publication

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)

Even if all direct human management of global forests ended immediately, their carbon sequestration potential would not be enough to curb ongoing climate change, according to a new study. The findings suggest that the planet’s current forests have only limited remaining carbon storage potential – even under the most unlikely of scenarios – to substantially mitigate atmospheric carbon dioxide (CO2) without major reductions in emissions. By capturing and storing carbon in biomass and soil organic matter, forests are integral to the global carbon cycle. As a result, the planet’s forests are often considered a central component in climate change policymaking, and many climate mitigation plans rely on forest-based carbon storage strategies to complement hard reductions in anthropogenic carbon emissions to achieve carbon neutrality. Despite this, the total amount of carbon that could realistically be stored in global forests remains poorly understood, nor has it been fully considered in climate mitigation strategies and policies. To address this, Caspar Roebroek and colleagues investigated the natural limits to additional carbon accumulation in the biomass of existing forests in the hypothetical absence of all direct human forest management activities, including wood harvesting, planting, and fire suppression, for example. Combining global maps of forest biomass in natural and managed forests with a novel machine learning, Roebroek et al. discovered that, under current climatic conditions and atmospheric CO2 concentrations, and the removal of all human forest management activities, existing global forests could increase their aboveground biomass by an additional ~44.1 petagrams of carbon. According to the authors, this represents an increase of roughly 15% more carbon than is currently stored in global forests, which would only offset about 4 years of worth of anthropogenic CO2 under current emission rates.

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JOURNAL

Science

DOI

10.1126/science.add5878 

ARTICLE TITLE

Releasing global forests from human management: How much more carbon could be stored?

ARTICLE PUBLICATION DATE

19-May-2023

POLITICAL ECOLOGY

In years after El Niño, global economy loses trillions

Study: Global downturn after Pacific climate pattern persists for several years

Peer-Reviewed Publication

DARTMOUTH COLLEGE

 

IMAGE: BY 2003, LOWER-INCOME TROPICAL NATIONS HAD EXPERIENCED THE GREATEST RESIDUAL LOSSES ON GROSS DOMESTIC PRODUCT (GDP) AS A RESULT OF THE 1997-98 EL NIÑO. THE COLOR SCALE INDICATES PERCENTAGE SHIFT IN GDP AS A RESULT OF THE 1997-98 EL NIÑO, FROM THE HIGHEST GAIN (BLUE) TO THE HIGHEST LOSS (RED). view more 

CREDIT: CHRIS CALLAHAN

In the years it strikes, the band of warm ocean water spanning from South America to Asia known as El Niño triggers far-reaching changes in weather that result in devastating floods, crop-killing droughts, plummeting fish populations, and an uptick in tropical diseases.

With El Niño projected to return this year, Dartmouth researchers report in the journal Science that the financial toll of the recurring climate pattern can persist for several years after the event itself—and cost trillions in lost income worldwide. The study is among the first to evaluate the long-term costs of El Niño and projects losses that far exceed those estimated by previous research.

El Niño is the warm phase of the El Niño-Southern Oscillation, the natural cycle of warm and cold temperatures in the tropical Pacific Ocean that includes La Niña, El Niño’s cooler counterpart. El Niño alters weather patterns worldwide and, in the United States, typically results in wetter, warmer winters for the West Coast and a milder hurricane season on the Atlantic seaboard.

The researchers spent two years examining global economic activity in the decades following the 1982-83 and 1997-98 El Niño events and found a "persistent signature" of slowed economic growth more than five years later. The global economy bled $4.1 trillion and $5.7 trillion, respectively, in the half-decade after each of these events, most of it borne by the world’s poorest nations in the tropics.

The researchers project that global economic losses for the 21st century will amount to $84 trillion as climate change potentially amplifies the frequency and strength of El Niño—even if current pledges by world leaders to reduce carbon emissions come to fruition. The researchers estimate that the El Niño predicted for 2023 alone could hold the global economy back by as much as $3 trillion by 2029.

Lead author Christopher Callahan, a doctoral candidate in geography at Dartmouth, said the study addresses an ongoing debate about how quickly societies rebound from major climate events such as El Niño.

"We can say with certainty that societies and economies absolutely do not just take a hit and recover," said Callahan, adding that their data suggested a downturn after El Niño could last as long as 14 years, if not longer.

"In the tropics and places that experience the effects of El Niño, you get a persistent signature during which growth is delayed for at least five years," he said. "The aggregate price tag on these events has not ever been fully quantified—you have to add up all the depressed growth moving forward, not just when the event is happening."

Senior author Justin Mankin, an assistant professor of geography, said the findings highlight a critical and understudied factor shaping the economic toll of global warming—year-to-year variations in climate conditions. While these swings are largely independent from global warming, they can amplify or diminish its effects. Once described as the "trunk of the tree of climate variability," El Niño is the largest and most important source of year-to-year climate variation, altering weather around the world and resonating across national economies.

When it comes to climate change, world leaders and the public rightfully focus on the unabated rise in the global average temperature, Mankin said. "But if you're estimating the costs of global warming without considering El Niño, then you are dramatically underestimating the costs of global warming."

"Our welfare is affected by our global economy, and our global economy is tied to the climate," Mankin said. "When you ask how costly climate change is, you can start by asking how costly climate variation is. We're showing here that such variation, as embodied in El Niño, is incredibly costly and stagnates growth for years, which led us to cost estimates that are orders of magnitudes larger than previous ones."

Callahan and Mankin found that the 1982-83 and 1997-98 events caused the gross domestic product of the United States to be approximately 3% lower in 1988 and 2003 than it would have been otherwise. But in 2003, the GDPs of coastal tropical nations such as Peru and Indonesia were lower by more than 10%.

“The global pattern of El Niño’s effect on the climate and on the prosperity of different countries reflects the unequal distribution of wealth and climate risk—not to mention the responsibility for climate change—worldwide,” Mankin said. “El Niño amplifies the wider inequities in climate change, disproportionately impacting the least resilient and prepared among us.”

"The duration and magnitude of the financial repercussions we uncovered suggests to me that we are maladapted to the climate we have," he said. "Our accounting dramatically raises the cost estimate of doing nothing. We need to both mitigate climate change and invest more in El Niño prediction and adaptation because these events will only amplify the future costs of global warming.”

The 2023 El Niño is predicted to come at a time when sea-surface temperatures are at an all-time high, Callahan said. The last major El Niño occurred in 2016 and made that year the hottest in recorded history. Global warming has only intensified in the seven years since. In addition, the world is coming out of an extended La Niña and the two phases can strengthen each other. The National Oceanic and Atmospheric Administration projects the chances of El Niño setting in by late summer as higher than 80%.

"The deck is potentially stacked for a really big El Niño," Callahan said. "Our results suggest that there will likely be a major economic toll that depresses economic growth in tropical countries for potentially up to a decade. The result could be trillions of dollars in productivity lost globally relative to a world without this El Niño."

The paper "Persistent effect of El Niño on global economic growth" was published May 18, 2023, by Science. The research was funded by a Graduate Research Fellowship (1840344) from the National Science Foundation; the Wright Center for the Study of Computation and Just Communities in Dartmouth’s Neukom Institute for Computational Science; and the Nelson A. Rockefeller Center for Public Policy and the Social Sciences.

###

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JOURNAL

Science

DOI

10.1126/science.adf2983 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Persistent effect of El Niño on global economic growth

ARTICLE PUBLICATION DATE

18-May-2023

Half of world's largest lakes losing water

Climate change, human consumption and sedimentation contributing to decline

Peer-Reviewed Publication

UNIVERSITY OF COLORADO AT BOULDER

 

IMAGE: LOOKING NORTHEAST, THE IMPERIAL VALLEY AND SALTON SEA IN SOUTHERN CALIFORNIA IS PHOTOGRAPHED FROM THE EARTH-ORBITING GEMINI-5 SPACECRAFT. PHOTO CREDIT: NASA. view more 

CREDIT: PHOTO CREDIT: NASA

More than 50 percent of the largest lakes in the world are losing water, according to a groundbreaking new assessment published today in Science . The key culprits are not surprising: warming climate and unsustainable human consumption.

But lead author Fangfang Yao, a CIRES visiting fellow, now a climate fellow at University of Virginia, said the news is not entirely bleak. With this new method of tracking lake water storage trends and the reasons behind them, scientists can give water managers and communities insight into how to better protect critical sources of water and important regional ecosystems.

“This is the first comprehensive assessment of trends and drivers of global lake water storage variability based on an array of satellites and models,” Yao said. 

He was motivated to do the research by the environmental crises in some of Earth's largest water bodies, such as the drying of the Aral Sea between Kazakhstan and Uzbekistan. 

So he and colleagues from the University of Colorado Boulder, Kansas State University, France, and Saudi Arabia created a technique to measure changes in water levels in nearly 2,000 of the world’s biggest lakes and reservoirs, which represent 95 percent of the total lake water storage on Earth. 

The team combined three decades of observations from an array of satellites with models to quantify and attribute trends in lake storage globally. 

Globally, freshwater lakes and reservoirs store 87 percent of the planet's water, making them a valuable resource for both human and Earth ecosystems. Unlike rivers, lakes are not well monitored, yet they provide water for a large part of humanity – even more than rivers.

But despite their value, long-term trends and changes to water levels have been largely unknown – until now.

“We have pretty good information on iconic lakes like Caspian Sea, Aral Sea and Salton Sea, but if you want to say something on a global scale, you need reliable estimates of lake levels and volume,” said Balaji Rajagopalan, a CIRES fellow, professor of engineering at CU Boulder, and co-author. “With this novel method …we are able to provide insights into global lake level changes with a broader perspective.” 

For the new paper, the team used 250,000 lake-area snapshots captured by satellites between 1992-2020 to survey the area of 1,972 of Earth’s biggest lakes. They collected water levels from nine satellite altimeters and used long-term water levels to reduce any uncertainty. For lakes without a long-term level record, they used recent water measurements made by newer instruments on satellites. Combining recent level measurements with longer-term area measurements allowed scientists to reconstruct the volume of lakes dating back decades. 

The results were staggering: 53 percent of lakes globally experienced a decline in water storage. The authors compare this loss with the magnitude of 17 Lake Meads, the largest reservoir in the United States.

To explain the trends in natural lakes, the team leveraged recent advancements in water use and climate modeling. Climate change and human water consumption dominated the global net decline in natural lake volume and water losses in about 100 large lakes, Yao said. “And many of the human and climate change footprints on lake water losses were previously unknown, such as the desiccations of Lake Good-e-Zareh in Afghanistan and Lake Mar Chiquita in Argentina.” 

Lakes in both dry and wet areas of the world are losing volume. The losses in humid tropical lakes and Arctic lakes indicate more widespread drying trends than previously understood.  

Yao and his colleagues also assessed storage trends in reservoirs. They found that nearly two-thirds of Earth’s large reservoirs experienced significant water losses. 

“Sedimentation dominated the global storage decline in existing reservoirs,” said Ben Livneh, also a co-author, CIRES fellow, and associate professor of engineering at CU Boulder. In long-established reservoirs—those that filled before 1992—sedimentation was more important than droughts and heavy rainfall years.

While the majority of global lakes are shrinking, 24 percent saw significant increases in water storage. Growing lakes tend to be in underpopulated areas in the inner Tibetan Plateau and Northern Great Plains of North America and in areas with new reservoirs such as the Yangtze, Mekong, and Nile river basins. 

The authors estimate roughly one-quarter of the world’s population, 2 billion people, resides in the basin of a drying lake, indicating an urgent need to incorporate human consumption, climate change, and sedimentation impacts into sustainable water resources management. 

And their research offers insight into possible solutions, Livneh said. “If human consumption is a large factor in lake water storage decline, then we can adapt and explore new policies to reduce large-scale declines.” 

This happened in one of the lakes the team studied, Lake Sevan in Armenia. Lake Sevan has seen an increase in water storage, in the last 20 years, which the authors linked to enforcement of conservation laws on water withdrawal since the early 2000s.

For an interactive map illustrating the findings, click here.

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JOURNAL

Science

DOI

10.1126/science.abo2812 

METHOD OF RESEARCH

Imaging analysis

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Satellites reveal widespread decline in global lake water storage

ARTICLE PUBLICATION DATE

18-May-2023

Global analysis reveals widespread decline in lake water storage worldwide

Peer-Reviewed Publication

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)

The amount of water stored in more than half of the largest lakes and reservoirs worldwide is declining, according to a new study. This drying is largely attributable to a warming climate and increased human impacts. The findings underscore the importance of accounting for these impacts in future surface water resources management strategies. Although they cover roughly 3% of the global land area, lakes hold 87% of Earth’s liquid surface fresh water. These features also provide essential ecosystem services and are key components in global biogeochemical processes. Many of these benefits are modulated by lake water storage (LWS), which can naturally fluctuate in response to local precipitation. However, direct human activities, like damming and water consumption, as well as ongoing climate change, increasingly threaten these crucial water resources. While it’s well known that the amount of water stored in some of the world’s largest lakes and human-managed reservoirs has progressively declined over recent years, the drivers behind these losses – particularly those related to human impacts and climate change – are poorly understood at the global scale. Combining global satellite measurements with climate and hydrologic models, Fangfang Yao et al. built a global dataset of decadal-scale trends in LWS from 1992 to 2020 for nearly 2,000 of the world’s largest lakes and reservoirs. Through their analysis, Yao et al. revealed a widespread decline in global LWS; according to the findings, 53% of these water bodies have experienced significant water losses over the last 28 years at a rate of roughly 22 gigatonnes (Gt) per year. The authors attribute much of the net volume loss in natural lakes to climate warming, increased evapotranspiration, and human water consumption, while sedimentation is to blame for storage loss in drying reservoirs. Yao et al. argue that the findings underscore the need for incorporating climate change and sedimentation impacts into sustainable water resources management. “Yao et al. estimated that nearly one-quarter of the world’s population lives in a basin with a large, drying lake,“ writes Sarah Cooley in a related Perspective. “Considering the importance of these lakes for ecosystem services, water supply, irrigation, and/or hydropower, the potential consequences of lake drying are both locally and globally important.”

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JOURNAL

Science

DOI

10.1126/science.abo2812 

ARTICLE TITLE

Satellites reveal widespread decline in global lake water storage

ARTICLE PUBLICATION DATE

19-May-2023

Humanity’s earliest recorded kiss occurred in Mesopotamia 4,500 years ago

Written sources document that kissing was practiced by the peoples of the ancient Middle East 4,500 years ago, conclude researchers from the University of Copenhagen and University of Oxford in a new article published in the journal Science.

Peer-Reviewed Publication

UNIVERSITY OF COPENHAGEN - FACULTY OF HUMANITIES

 

IMAGE: BABYLONIAN CLAY MODEL SHOWING A NUDE COUPLE ON A COUCH ENGAGED IN SEX AND KISSING. DATE: 1800 BC. view more 

CREDIT: © THE TRUSTEES OF THE BRITISH MUSEUM

Recent research has hypothesised that the earliest evidence of human lip kissing originated in a very specific geographical location in South Asia 3,500 years ago, from where it may have spread to other regions, simultaneously accelerating the spread of the herpes simplex virus 1.

But according to Dr Troels Pank Arbøll and Dr Sophie Lund Rasmussen, who in a new article in the journal Science draw on a range of written sources from the earliest Mesopotamian societies, kissing was already a well-established practice 4,500 years ago in the Middle East. And probably much earlier, moving the earliest documentation for kissing back 1,000 years compared to what was previously acknowledged in the scientific community.

“In ancient Mesopotamia, which is the name for the early human cultures that existed between the Euphrates and Tigris rivers in present-day Iraq and Syria, people wrote in cuneiform script on clay tablets. Many thousands of these clay tablets have survived to this day, and they contain clear examples that kissing was considered a part of romantic intimacy in ancient times, just as kissing could be part of friendships and family members’ relations,” says Dr Troels Pank Arbøll, an expert on the history of medicine in Mesopotamia.

He continues:

“Therefore, kissing should not be regarded as a custom that originated exclusively in any single region and spread from there but rather appears to have been practiced in multiple ancient cultures over several millennia.”

Dr Sophie Lund Rasmussen adds:

“In fact, research into bonobos and chimpanzees, the closest living relatives to humans, has shown that both species engage in kissing, which may suggest that the practice of kissing is a fundamental behaviour in humans, explaining why it can be found across cultures.”

Kissing as potential transmitter of disease

In addition to its importance for social and sexual behaviour, the practice of kissing may have played an unintentional role in the transmission of microorganisms, potentially causing viruses to spread among humans.

However, the suggestion that the kiss may be regarded as a sudden biological trigger behind the spread of particular pathogens is more doubtful. The spread of the herpes simplex virus 1, which researchers have suggested could have been accelerated by the introduction of the kiss, is a case in point:

“There is a substantial corpus of medical texts from Mesopotamia, some of which mention a disease with symptoms reminiscent of the herpes simplex virus 1,” Dr Arbøll remarks.

He adds that the ancient medical texts were influenced by a variety of cultural and religious concepts, and it therefore must be emphasized that they cannot be read at face value.

“It is nevertheless interesting to note some similarities between the disease known as buʾshanu in ancient medical texts from Mesopotamia and the symptoms caused by herpes simplex infections. The bu’shanu disease was located primarily in or around the mouth and throat, and symptoms included vesicles in or around the mouth, which is one of the dominant signs of herpes infection.”

“If the practice of kissing was widespread and well-established in a range of ancient societies, the effects of kissing in terms of pathogen transmission must likely have been more or less constant”, says Dr Rasmussen.

Dr Arbøll and Dr Rasmussen conclude that future results emerging from research into ancient DNA, inevitably leading to discussions about complex historical developments and social interactions – such as kissing as a driver of early disease transmission - will benefit from an interdisciplinary approach.

Read the article “The ancient history of kissing” in Science.

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JOURNAL

Science

DOI

10.1126/science.adf0512 

METHOD OF RESEARCH

Commentary/editorial

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

The ancient history of kissing

ARTICLE PUBLICATION DATE

19-May-2023

Ancient history of kissing and its role in disease transmission

Reports and Proceedings

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)

In a Perspective, Troels Arbøll and Sophie Rasmussen review the ancient history of kissing, particularly the emergence of romantic-sexual kissing in Mesopotamia more than 4000 years ago and its role in the evolution and spread of orally transmitted diseases like herpes simplex virus 1 (HSV-1). They say the kiss cannot be regarded as a sudden biological trigger causing a spread of specific pathogens, as some research has recently proposed. “Evidence indicates that kissing was a common practice in ancient times, potentially representing a constant influence on the spread of orally transmitted microbes, such as HSV-1,” write Arbøll and Rasmussen. Humans generally exhibit two main types of kissing – the friendly-parental kiss and the romantic-sexual kiss. Although research has suggested that friendly-parental kissing is a ubiquitous behavior among humans across time and geography, romantic-sexual kissing is not culturally universal and tends to occur in stratified societies; Arbøll and Rasmussen highlight a body of overlooked evidence of romantic-sexual kissing occurring in ancient Mesopotamian texts from 2500 BCE. Beyond its importance for social and sexual behavior, the emergence and act of this form of kissing may have had a secondary, unintended effect on disease transmission. Recent paleogenomics research has shown that common kiss-transmissible pathogens of today, including HSV-1, Epstein-Barr virus, and human parvovirus B19, were present in ancient historical and even prehistorical periods. Arbøll and Rasmussen review ancient DNA, cultural works of art, and ancient medical records to show that the presence of kissing-transmitted diseases may be more ancient and widespread than some recent studies have suggested. “It … seems unlikely that kissing would have arisen as an immediate behavioral adaptation in other contemporary societies, which inadvertently accelerated disease transmission,” they say.

This Perspective follows up on the conclusions of a July 2022 study published in Science Advances, which linked a shift in lineages of HSV-1 in ancient humans to the emergence of sexual-kissing behavior during the Bronze Age.

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JOURNAL

Science

DOI

10.1126/science.adf0512 

ARTICLE TITLE

The ancient history of kissing

ARTICLE PUBLICATION DATE

19-May-2023