Making a memory positive or negative

Salk researchers pinpoint a neurotransmitter that helps assign positive or negative emotions to a memory

Peer-Reviewed Publication

SALK INSTITUTE

 

IMAGE: EXPRESSION OF VARIOUS GENES AND PROTEINS (WHITE, RED, AND GREEN) IN NEURONS AMONGST MOUSE BRAIN CELLS (BLUE). view more 

CREDIT: SALK INSTITUTE

LA JOLLA—(July 20, 2022) Researchers at the Salk Institute and colleagues have discovered the molecule in the brain responsible for associating good or bad feelings with a memory. Their discovery, published in Nature on July 20, 2022, paves the way for a better understanding of why some people are more likely to retain negative emotions than positive ones—as can occur with anxiety, depression or post-traumatic stress disorder (PTSD).

“We’ve basically gotten a handle on the fundamental biological process of how you can remember if something is good or bad,” says senior author Kay Tye, a professor in Salk’s Systems Neurobiology Laboratory and a Howard Hughes Medical Institute Investigator. “This is something that’s core to our experience of life, and the notion that it can boil down to a single molecule is incredibly exciting.”

For a human or animal to learn whether to avoid, or seek out, a particular experience again in the future, their brain must associate a positive or negative feeling, or “valence” with that stimulus. The brain’s ability to link these feelings with a memory is called “valence assignment.”

In 2016, Tye discovered that a group of neurons in the brain’s basolateral amygdala (BLA) helps assign valence when mice are learning. One set of BLA neurons was activated with positive valence, as the animals learned to associate a tone with a sweet taste. A separate set of BLA neurons was activated with negative valence, as the animals learned to associate a different tone with a bitter taste.

“We found these two pathways—analogous to railroad tracks—that were leading to positive and negative valence, but we still didn’t know what signal was acting as the switch operator to direct which track should be used at any given time,” says Tye, holder of the Wylie Vale Chair.

In the new study, the researchers homed in on the importance of the signaling molecule neurotensin to these BLA neurons. They already knew that neurotensin is a neuropeptide produced by the cells associated with valence processing, but so are a few other neurotransmitters. So, they used CRISPR gene editing approaches to selectively remove the gene for neurotensin from the cells—the first time that CRISPR has been used to isolate specific neurotransmitter function.

Without neurotensin signaling in the BLA, mice could no longer assign positive valence and didn’t learn to associate the first tone with a positive stimulus. Interestingly, the absence of neurotensin did not block negative valence. The animals instead became even better at negative valence, having a stronger association between the second tone and a negative stimulus.

The findings suggest that the brain’s default state is to have a bias toward fear—the neurons associated with negative valence are activated until neurotensin is released, switching on the neurons associated with positive valence. From an evolutionary perspective, Tye says, this makes sense because it helps people avoid potentially dangerous situations—and it probably resonates with people who tend to find the worst in a situation.

CAPTION

From left: Kay Tye and Hao Li

CREDIT

Salk Institute

In further experiments, Tye and her team showed that high levels of neurotensin promoted reward learning and dampened negative valence, further supporting the idea that neurotensin is responsible for positive valence.

“We can actually manipulate this switch to turn on positive or negative learning,” says co-first author Hao Li, a postdoctoral fellow in the Tye Lab. “Ultimately, we’d like to try to identify novel therapeutic targets for this pathway.”

The researchers still have questions about whether levels of neurotensin can be modulated in people’s brains to treat anxiety or PTSD. They are also planning future studies to probe what other brain pathways and molecules are responsible for triggering the release of neurotensin.

Other authors of the paper were Matilde Borio, Mackenzie Lemieux, Austin Coley, Avraham Libster, Aneesh Bal, Caroline Jia, Jasmin Revanna, Kanha Batra, Kyle Fischer, Laurel Keyes, Nancy Padilla-Coreano and Romy Wichmann of Salk; Praneeth Namburi, Jacob Olson, Anna Beyeler, Gwendolyn Calhoon, Natsuko Hitora-Imamura, Ada Felix-Ortiz, Verónica de la Fuente, Vanessa Barth, Hunter King, Ehsan Izadmehr, Cody Siciliano and Ila Fiete of MIT; Xin Jin, Sourav Choudhury, Xi Shi and Feng Zhang of the Broad Institute of MIT and Harvard; Huan Wang and Yulong Li of Peking University; and Kenneth McCullough and Kerry Ressler of Harvard Medical School.

The work was supported by the JPB Foundation, PIIF, PNDRF, JFDP, Alfred P. Sloan Foundation, New York Stem Cell Foundation, Klingenstein Foundation, McKnight Foundation, Clayton Foundation, National Institutes of Health (R01-MH102441, RF1-AG047661, DP2-DK102256, DP1-AT009925, F32 MH115446-01 and K99 DA055111), the Brain and Behavior Research Foundation, MEXT (15K21744, 17H06043), the Uehara Memorial Foundation, Singleton, Leventhal and Whitaker fellowships, a fellowship from the Swiss National Science Foundation and a Fulbright scholarship.

About the Salk Institute for Biological Studies:

Every cure has a starting point. The Salk Institute embodies Jonas Salk’s mission to dare to make dreams into reality. Its internationally renowned and award-winning scientists explore the very foundations of life, seeking new understandings in neuroscience, genetics, immunology, plant biology and more. The Institute is an independent nonprofit organization and architectural landmark: small by choice, intimate by nature and fearless in the face of any challenge. Be it cancer or Alzheimer’s, aging or diabetes, Salk is where cures begin. Learn more at: salk.edu.

VIDEO Making a memory positive or ne [VIDEO] | EurekAlert! Science News Releases

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JOURNAL

Nature

DOI

10.1038/s41586-022-04964-y 

ARTICLE TITLE

Neurotensin orchestrates valence assignment in the amygdala

ARTICLE PUBLICATION DATE

20-Jul-2022

Burning woody biomass in power plants could reduce carbon

Peer-Reviewed Publication

UNIVERSITY OF GEORGIA

According to a new study by researchers in the University of Georgia’s Warnell School of Forestry and Natural Resources, replacing coal in Georgia’s power plants with woody biomass could not only meet Georgia’s power needs, but reduce carbon emissions.

The research calculated both economic and environmental factors to provide a comprehensive picture of the impact of replacing coal with timber for a 50-year period.

As one of the largest consumers of coal in the Southeast, Georgia burns over 7 million tons each year. This accounts for nearly two-thirds of all carbon emissions from Georgia’s power sector. Replacing coal with another fuel source could reduce those emissions by 43%, according to Farhad Hossain Masum, a Ph.D. graduate and first author of the study.

Masum’s research started in 2017 when he began looking for a suitable feedstock to replace coal in power plants. Early on, the research showed that woody biomass, like wood chips and the residue from logging, could be more economical and better for the environment than other renewable fuel sources.

“Torrefied pulpwood and logging residue can be used in coal-fired power plants without making major upgrades to the plant. This makes it a great alternative to coal, especially in forest-rich southern states,” said Puneet Dwivedi, an associate professor at Warnell School, Masum’s advisor and co-author of the study.

The torrefaction of wood is like roasting coffee. Wood is heated in a controlled environment, usually around 400 degrees Fahrenheit. The heat removes moisture and chemically alters the wood. This process reduces the biomass of the wood by around 25%, turns it into a charcoal-like substance, and gives it a similar energy density to coal.

“Based on previous research, we knew this could work, but we weren’t sure of the best way to add torrefied wood as a fuel source. We looked at a few different models to see what would happen if we implemented these programs across Georgia,” said Masum.

First, they quantified the impact of making no changes and continuing to burn coal. Second, they studied using pulpwood as a fuel source; a portion of trees usually with trunks ranging from 5 to 9 inches in diameter. Third, they measured the impact of using both pulpwood and logging residues to replace coal.

They found the third scenario, using both pulpwood and logging residues, would be the most carbon-efficient way to generate electricity for Georgia. This method could reduce 43% of carbon emissions from coal-fired power plants without major upgrades to the facilities.

However, it would require an additional 100,000 acres of forestland to be harvested each year. In the scenario, these trees would be harvested from six southern states.

This is still more efficient than using only pulpwood, according to the researchers. If only pulpwood was used to manufacture the torrefied wood chips, an additional 340,000 acres of forestland would need to be harvested annually to replace Georgia’s coal.

“Our results indicate that Georgia and Alabama could supply most of the additional wood required for biopower generation,” said Masum.

Even though more trees would need to be cut to replace coal, the research showed that this would benefit the environment by keeping carbon out of the atmosphere. Coal releases significantly more non-renewable carbon than torrefied wood when burned. In general, this carbon can be considered extra carbon that was not in the environment but sequestered underground.

On the other hand, trees soak up carbon from the atmosphere as they grow. While some of this carbon may be re-released, it results in a net reduction of carbon from the atmosphere. This reduction was the highest when both pulpwood and logging residues replaced coal for electricity generation.

Integrating logging residues into the energy supply chain would also allow foresters to make better use of every part of the tree. Currently, most logging residue in the southeast is left in the field and burned.

“The use of wood-based electricity will not only reduce the carbon footprint of the state, but it will potentially create local jobs, boost forest health, increase the income of rural households, and ensure the flow of forest-based ecosystem services,” said Dwivedi.

“However, a need exists to evaluate the economic and welfare impacts of any initiative to replace coal-based power generation in Georgia to tackle issues operating at the interface of energy access and climate change.”

Co-authors include Weiwei Wang of the Nanjing University of Information Science and Technology in Nanjing, China, and Greg Colson in the Department of Agricultural and Applied Economics at the University of Georgia. The research was supported by a McIntire-Stennis grant from the United States Department of Agriculture.

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JOURNAL

Journal of Environmental Management

DOI

10.1016/j.jenvman.2022.115060 

ARTICLE TITLE

Replacing coal in Georgia's power plants with woody biomass to increase carbon benefit: A mixed integer linear programming model

A history of rye: How early farmers made plants genetically less flexible

Peer-Reviewed Publication

MARTIN-LUTHER-UNIVERSITÄT HALLE-WITTENBERG

 

IMAGE: DOMESTICATED RYE GROWN IN HALLE (SAALE), GERMANY view more 

CREDIT: UNI HALLE / STEVEN DREISSIG

Over the course of many thousands of years, humans turned rye into a cultivated plant. In doing so, they have considerably limited its genetic flexibility. Today, wild rye not only has a more diverse genetic make-up, it is able to recombine this more freely than its domesticated cousins. A research team led by Martin Luther University Halle-Wittenberg (MLU) and the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) has demonstrated this in a new study published in the scientific journal "Molecular Biology and Evolution". The results also explain why cultivated rye is less resistant than wild species to developments such as climate change.

In their study, the team investigated various properties and the genetic material of 916 wild and domesticated rye plants from different regions in Europe and Asia. They were particularly interested in the so-called recombining regions of rye. In essence, this describes how often the genetic material within a plant mixes along a chromosome during cell division. "The process of recombination plays an important role in a species’ evolution because it enables two beneficial gene variants to combine," explains Dr Steven Dreissig from MLU. At the same time, useful variants can also be separated from ones that are less beneficial. The larger the recombination landscape, the more plants are able to flexibly recombine their genetic material.

For early farmers, however, this process was disadvantageous: agriculture relies on uniform plants with more or less there the same properties and the same genetic material. In the case of rye, says Dreissig, the situation is aggravated by the fact that the plants depend on cross-pollination; unlike barley or wheat, they are unable to self-pollinate. "Rye pollen can travel up to several kilometres. This allows populations that are separated spatially to remain in contact and exchange genetic material," says Dreissig.

People started growing cereals, such as barley or wheat, around 12,000 years ago. Most of the varieties established today originated in the Fertile Crescent region of the Middle East. "Rye is assumed to have first spread to Europe as a weed and could only be domesticated there much later because there were no disturbing wild varieties," says Dr Martin Mascher from IPK, who is also a member of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig.

Their new analyses have allowed the researchers to reconstruct the distribution of rye and recreate a kinship network from Asia to Central Europe. The wider the distance between the individual locations, the greater the differences in the recombination landscape of the plants. "We actually found major differences between domesticated and wild rye, especially in the non-recombining regions. In cultivated rye, the recombining regions are significantly smaller than in the weed-like plants, such as those still found today in Turkey," says Dreissig. This is advantageous for cultivated plants because it makes plants with desirable properties, for example firm ears and large grains, more uniform and controllable. Wild rye, on the other hand, benefits from this genetic flexibility, which allows it to react better to disturbance factors, such as a changing climate.

The team also identified a gene region that appears to play a major role in the flexibility of the genetic material. In doing so, they also found a gene that was already known to influence recombining regions in yeast.

 

The study was funded by the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG) and the Federal Ministry of Education and Research (BMBF).

 

Study: Schreiber M. et al. Recombination Landscape Divergence Between Populations is Marked by Larger Low-Recombining Regions in Domesticated Rye. Molecular Biology and Evolution (2022). doi: 10.1093/molbev/msac131

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JOURNAL

Molecular Biology and Evolution

DOI

10.1093/molbev/msac131 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Recombination Landscape Divergence Between Populations is Marked by Larger Low-Recombining Regions in Domesticated Rye

Human activities increase likelihood of more extreme heatwaves, researchers find

Peer-Reviewed Publication

INSTITUTE OF ATMOSPHERIC PHYSICS, CHINESE ACADEMY OF SCIENCES

 

IMAGE: SHADING REPRESENTS SURFACE AIR TEMPERATURE ANOMALIES, AND THE GREEN VECTOR DENOTES JETSTREAM (A NARROW BAND OF VERY STRONG WESTERLY AIR CURRENTS NEAR THE ALTITUDE OF THE TROPOPAUSE). TWO BLUE VECTORS INDICATE THAT THE HEATWAVE IS RELATED TO ANOMALOUS CIRCULATIONS IN THE NORTH PACIFIC AND THE ARCTIC. view more 

CREDIT: JIAYU ZHENG

July 19 was the hottest day ever recorded in the United Kingdom, with temperatures surpassing 40 degrees Celsius (about 104 degrees Fahrenheit). The heatwave serves as an early preview of what climate forecasters theorized will be typical summer weather in the U.K. in 2050. The heat continues across Europe today, as well as in the United States, where more than a third of the country is under heat warnings.

The temperatures harken back to just over a year ago when nearly 1,500 people died during a late June heatwave that more than doubled average temperatures in the United States and Canada.

Will temperatures continue to rise, leading to more frequent extreme heat events?

Yes, according to the latest analysis of the atmospheric circulation patterns and human-caused emissions that led to the 2021 heatwave in North America. The findings, published on July 22 in Advances in Atmospheric Sciences, may also explain the U.K.'s current heatwave.

The research team found that greenhouse gases are the primary reason for increased temperatures in the past and will likely continue to be the main contributing factor, with simulations showing that extreme heatwave events will increase by more than 30% in the coming years. Almost two-thirds of that increased probability is the result of greenhouse gases, according to their results.

“An extraordinary and unprecedented heatwave swept western North America in late June of 2021, resulting in hundreds of deaths and a massive die-off of sea creatures off the coast as well as horrific wildfires,” said co-corresponding author Chunzai Wang, a researcher in the Southern Marine Science and Engineering Guangdong Laboratory and head of the State Key Laboratory of Tropical Oceanography at the South China Sea Institute of Oceanology, Chinese Academy of Sciences (CAS).

“In this paper, we studied the physical processes of internal variability, such as atmospheric circulation patterns, and external forcing, such as anthropogenic greenhouse gases.”

Atmospheric circulation patterns describe how air flows and influences surface air temperatures around the planet, both of which can change based on natural warming from the Sun and atmospheric internal variability, as well as Earth’s rotation. These configurations are responsible for daily weather, as well as the long-term patterns comprising climate. . Using observational data and climate models, the researchers identified that three atmospheric circulation patterns co-occurred during the 2021 heatwave: the North Pacific pattern, the Arctic-Pacific Canada pattern and the North America pattern.

“The North Pacific pattern and the Arctic-Pacific Canada pattern co-occurred with the development and mature phases of the heatwave, whereas the North America pattern coincided with the decaying and eastward movements of the heatwave,” Wang said. “This suggests the heatwave originated from the North Pacific and the Arctic, while the North America pattern ushered the heatwave out.”

But atmospheric circulation patterns can co-occur — and have before — without triggering an extreme heatwave, so how much was the 2021 event influenced by human activities? Wang and the team used the internationally curated, tested and assessed models from the World Climate Research Programme, specifically the Detection Attribution Model Comparison models of the Coupled Model Intercomparison Project Phase 6 (CMIP6).

“From the CMIP6 models, we found that it is likely that global warming associated with greenhouse gases influences these three atmospheric circulation pattern variabilities, which, in turn, led to a more extreme heatwave event,” Wang said. “If appropriate measures are not taken, the occurrence probability of extreme heatwaves will increase and further impact the ecological balance, as well as sustainable social and economic development.”

Other contributors include co-corresponding author Jiayu Zheng and two students from the University of CAS: Wei Lin and Yuqing Wang.

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JOURNAL

Advances in Atmospheric Sciences

DOI

10.1007/s00376-022-2078-2 

ARTICLE TITLE

Unprecedented Heatwave in Western North America during Late June of 2021: Roles of Atmospheric Circulation and Global Warming

ARTICLE PUBLICATION DATE

22-Jul-2022

Preterm birth is more likely with exposure to phthalates

Rutgers contributes to a National Institutes of Health study of pregnant women confirming link with chemicals that could put pregnancy at risk

Peer-Reviewed Publication

RUTGERS UNIVERSITY

A Rutgers researcher was part of a National Institutes of Health study that found pregnant women who were exposed to chemical compounds known as phthalates during pregnancy had an increased risk of preterm birth.

Phthalates are industrial chemicals used in personal-care products, such as cosmetics, as well as solvents, detergents and in food packaging.

After examining data from 6,045 pregnant women in the U.S., researchers found that women with higher concentrations of several phthalate metabolites in their urine were more likely to deliver their babies preterm—or delivering three or more weeks before a mother’s due date. The study was published in the journal JAMA Pediatrics.

“Preterm birth is one of the most poorly understood, intractable challenges in maternal-child health,” said author Emily Barrett, an associate professor at the Rutgers School of Public Health and a member of the Environmental and Occupational Health Sciences Institute.

“This study provides compelling evidence that everyday chemicals in our environment are part of the problem,” Barrett said. Conducting the largest study in the United States to date on this topic, researchers pooled data from 16 studies conducted throughout the U.S. that had individual participant data on prenatal urinary phthalate metabolites (which represent exposure to phthalates) as well as the timing of delivery of the study participants. Pregnant women participating in in the study delivered babies between 1983 and 2018. Nine percent, or 539, of the women delivered preterm births. Phthalate metabolites were detected in more than 96 percent of urine samples.

The researchers developed statistical models to examine whether exposure to phthalates were associated with preterm birth. Higher concentrations of most phthalate metabolites examined were associated with slightly higher odds of preterm birth. Exposure to four of the 11 phthalates in pregnancy was associated with a significantly greater probability of having a preterm birth. The most consistent findings were for exposure to a phthalate that is used commonly in personal-care products such as nail polish and cosmetics.

The researchers also used computational models to simulate hypothetical interventions that could reduce phthalate exposure. They estimated that reducing the phthalate exposure by even 50 percent could reduce preterm birth by 12 percent. The potential interventions could be behavioral, such as selecting personal-care products that don’t contain phthalates (if listed on label); voluntary actions from companies to eliminate phthalates from their products; or regulatory in nature.

“Our data demonstrate that if we could reduce our exposures to phthalates, we could make considerable progress towards reducing our unacceptably high rates of preterm birth,” said Barrett.

Eating fresh, home-cooked food as often as possible, avoiding processed food that comes in plastic and selecting fragrance-free products or those labeled as “phthalate free,” are some examples of ways pregnant people can reduce their exposure to the chemicals.

The researchers are conducting additional studies to better understand the mechanisms by which exposure to phthalates can impact pregnancy and determine if there are effective ways for mothers to reduce their exposure.

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JOURNAL

JAMA Pediatrics

DOI

10.1001/jamapediatrics.2022.2252 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Associations Between Prenatal Urinary Biomarkers of Phthalate Exposure and Preterm Birth

ARTICLE PUBLICATION DATE

11-Jul-2022

Our Synthetic Environment - Libcom.org

https://files.libcom.org › files › Bookchin M. Our ...

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by M Bookchin · Cited by 270 — The link between environment and illness is becoming difficult to ignore. This is not to say that every degenerative disease is environmentally induced. But it ...

101 pages

Mammals were not the first to be warm-blooded

Karoo fossils provide “smoking gun” on clues to when warm-bloodedness evolved in pre-mammalian ancestors

Peer-Reviewed Publication

UNIVERSITY OF THE WITWATERSRAND

 

IMAGE: A WARM-BLOODED MAMMAL ANCESTOR BREATHING OUT HOT HAIR IN A FRIGID NIGHT. view more 

CREDIT: LUZIA SOARES

Endothermy, or warm-bloodedness, is the ability of mammals and birds to produce their own body heat and control their body temperature. 

This major difference with the cold-blooded reptiles underpins the ecological dominance of mammals in almost every ecosystem globally. Until now, it was not known exactly when endothermy originated in mammalian ancestry. A team of international scientists, including researchers from the University of the Witwatersrand (Wits University) in Johannesburg, South Africa, has found the smoking gun of this key evolutionary event in the inner ears of fossils from South Africa and around the globe.

A new study suggests that endothermy appeared in mammalian ancestors about 233 million years ago, well before the origin of mammals, which occurred about 200 million years ago. This study, titled Inner ear biomechanics reveals Late Triassic origin of mammalian endothermy is published in Nature. 

“For the first time, we are able to trace through evolution the direct consequence of the origin of endothermy on the skeletal anatomy of our pre-mammalian ancestors,” says Dr Julien Benoit, Senior Researcher in Palaeontology at the Evolutionary Studies Institute at Wits University. “This is an exciting time for our field of study.”

The intuition

The inner ear is not only the organ of hearing, but also houses the organ of balance: the semicircular canals. The three semicircular canals of the inner ear are oriented in the three dimensions of space and are filled with a fluid that flows in the canals as the head moves and activates receptors to tell the brain the exact three-dimensional position of the head and body. The viscosity, or runniness, of this fluid (called the endolymph) is of paramount importance for the balance organ to efficiently detect head rotation and aid balance. 

As for any other fluid, the viscosity of the endolymph changes with body temperature, just like a piece of butter turns from solid to liquid in a warm pan. Because of this physical property, the viscosity of the endolymph would be altered by the evolution of a higher body temperature. However, this change of viscosity cannot be left unchecked because the balance organ would stop working properly. The semicircular canals of the inner ear must adapt to the new viscosity imposed by higher body temperature: they have to change their geometry. 

The key intuition of the two lead authors of the discovery, Dr Ricardo Araújo (University of Lisbon) and Dr Romain David (Natural History Museum of Paris), was to realise that this change in the semicircular canals shape would be easy to trace through geologic time using fossils. Pinpointing the species in which this change of geometry occurred would work as an accurate guide to when endothermy evolved: the smoking gun identifying when mammalian ancestors transitioned from cold-blooded to warm-blooded.

“Until now, semicircular canals were generally used to predict locomotion of fossil organisms. However, by carefully looking at their biomechanics, we figured that we could also use them to infer body temperatures. This is because, like honey, the fluid contained inside semicircular canals gets less viscous when temperature increases, impacting function. Hence, during the transition to endothermy, morphological adaptations were required to keep optimal performances, and we could track them in mammal ancestors,” says Dr Romain David, Post-Doctoral Researcher at the Natural History Museum and Lead Author on the paper.

The contribution of Karoo fossils

The team found that the inner ear canals geometry adapted to a relatively abrupt change in endolymph viscosity some 233 million years ago, indicating that the overall body temperature of mammal ancestors became warmer at this time. 

Fossils from the South African Karoo played a key role in this discovery, in part because of the wealth of fossils of mammal ancestors that the Karoo-aged rocks have produced in more than a hundred years of study. 

South African fossils offer an unbroken record of the evolution of life during an interval of almost 100 million years, documenting the transformation from reptilian-like animals (the therapsids) to mammals in exquisite detail. In addition, because the Karoo was situated closer to the South Pole at that time as a result of continental drift, the warmer body temperature suggested by the geometry of the inner ear cannot be due to an overall warmer climate. 

“As the South African climate was colder on average, the change in inner ear fluid viscosity can only have been caused by a generally warmer body temperature in mammalian ancestors,” says Benoit.

Using cutting edge CT-scanning techniques and 3D modelling, the researchers were able to reconstruct the inner ear of dozens of mammalian ancestors from the South African Karoo and elsewhere in the world, and managed to point out exactly which species had an inner ear anatomy consistent with a warmer body temperature, and which ones did not. 

A change of paradigmn

Until now the general expectation was that endothermy arose very close to the Permo-Triassic boundary, about 252 million years ago, or perhaps closer to the origin of mammals 200 million years ago. The new results suggest that endothermy appeared in mammalian ancestors some 233 million years ago. This new date is consistent with the recent findings that many of the traits usually associated with “mammalness”, such as whiskers and fur, also evolved earlier than previously expected. More importantly, the results support that the evolutionary transition to warmbloodedness was unexpectedly fast.

“Contrary to current scientific thinking, our paper surprisingly demonstrates that the acquisition of endothermy seems to have occurred very quickly in geological terms, in less than a million years,” says Dr Ricardo Araújo, Junior Researcher at Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, University of Lisbon and Lead Author on the paper. “It was not a gradual, slow process over tens of millions of years as previously thought, but maybe was attained quickly when triggered by novel mammal-like metabolic pathways and origin of fur.”

“The origin of mammalian endothermy is one of the great unsolved mysteries of paleontology”, says Dr Kenneth D. Angielczyk, MacArthur Curator of Paleomammalogy at Field Museum of Natural History, USA and Senior Author on the paper. 

“Many different approaches have been used to try to predict when it first evolved, but they have often given vague or conflicting results. We think our method shows real promise because it has been validated using a very large number of modern species, and it suggests that endothermy evolved at a time when many other features of the mammalian body plan were also falling into place.”

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JOURNAL

Nature

ARTICLE TITLE

Inner ear biomechanics reveals Late Triassic origin of mammalian

ARTICLE PUBLICATION DATE

20-Jul-2022

The size of mammal ancestors’ ear canals reveal when warm-bloodedness evolved

Higher body temperatures went hand-in-hand with runnier “ear fluid” and narrower ear canals

Peer-Reviewed Publication

FIELD MUSE

CAPTION

Size differences between inner ears (in grey) of warm-blooded mammaliamorphs (on the left) and cold-blooded, earlier synapsids (on the right). Inner ears are compared for animals of similar body sizes.

CREDIT

Credit: Romain David and Ricardo Araújo

One of the things that makes mammals, mammals is that we’re warm-blooded-- our bodies have high metabolisms that maintain our internal temperature independent of our surroundings, unlike cold-blooded animals like lizards that have to bask in the sun. Among modern animals, only mammals and birds are warm-blooded, and our ability to keep ourselves warm has enabled mammals to survive in icy weather and make long migrations. But it’s been a mystery exactly when mammals evolved their high metabolisms. In a new study in Nature, scientists point to an unlikely source for determining when ancient mammal ancestors became warm-blooded: the size of tiny structures in their inner ears.

It’s hard to tell whether a fossil animal was warm-blooded-- we can’t take the temperature of a creature that lived hundreds of millions of years ago, and we can only guess at whether its behavior matched an active, warm-blooded metabolism or a slower cold-blooded one. But a team of researchers led by London’s Natural History Museum, the University of Lisbon’s Instituto Superior Técnico, and the Field Museum in Chicago realized that animals’ ears provide an indirect clue about their body temperatures.

All vertebrate animals’ ears contain tiny canals filled with fluid that helps us balance. The viscosity, or runniness, of that fluid changes based on temperature, and our inner ears have evolved different sizes so that it can flow correctly. Cold-blooded animals’ ear fluid is cooler and thicker, so it needs wider spaces to travel through, while warm-blooded animals have runnier ear fluid, so our semicircular canals don’t need to be as big.

“Until now, semicircular canals were generally used to predict locomotion of fossil organisms. However, by carefully looking at their biomechanics, we figured that we could also use them to infer body temperatures,” says Romain David, a post-doctoral researcher at the Natural History Museum and one of the study’s lead authors. “This is because, like honey, the fluid contained inside semicircular canals gets less viscous when temperature increases, impacting function. Hence, during the transition to endothermy, morphological adaptations were required to keep optimal performances, and we could track them in mammal ancestors.”

To track these evolutionary changes, the researchers compared the sizes of the inner ear canals of 341 animals, including 243 living species and 64 extinct ones. They found that mammal ancestors didn’t develop the kinds of inner ear structures ideal for warm-blooded animals until 233 million years ago-- nearly 20 million years later than scientists had previously thought warm-bloodedness evolved. And, based on when those differently-sized semicircular canals showed up in the fossil record, it seems that when mammal ancestors did evolve warm-bloodedness, it happened much more quickly than scientists had thought, around the same time that proto-mammals started to evolve whiskers, fur, and specialized backbones. The evolution of fur and warm-bloodedness at about the same time especially make sense because fur traps the body heat generated by a higher metabolism, helping keep the body at the high temperature it needs to thrive.

“Contrary to current scientific thinking, our paper surprisingly demonstrates that the acquisition of endothermy seems to have occurred very quickly in geological terms, in less than a million years,” says Ricardo Araújo, junior researcher at Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, University of Lisbon and one of the paper’s lead authors. “It was not a gradual, slow process over tens of millions of years as previously thought, but maybe was attained quickly when triggered by novel mammal-like metabolic pathways and origin of fur.”

The study’s senior author, Ken Angielczyk, says he’s excited by how the study helps answer one of the longest-standing questions about the evolution of mammals.

“The origin of mammalian endothermy is one of the great unsolved mysteries of paleontology. Many different approaches have been used to try to predict when it first evolved, but they have often given vague or conflicting results,” says Angielczyk, the Field Museum’s MacArthur Curator of Paleomammalogy. “We think our method shows real promise because it has been validated using a very large number of modern species, and it suggests that endothermy evolved at a time when many other features of the mammalian body plan were also falling into place.”

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JOURNAL

Nature

DOI

10.1038/s41586-022-04963-z 

ARTICLE TITLE

Inner ear biomechanics reveals the Late Triassic origin of mammalian endothermy

ARTICLE PUBLICATION DATE

20-Jul-2022

Beliefs in conspiracy theories may not be increasing

New findings challenge widespread perceptions by the public, scholars, journalists, and policymakers

Peer-Reviewed Publication

PLOS

 

IMAGE: “CONSPIRACY” TYPED OUT ON A TYPEWRITER. view more 

CREDIT: MARKUS WINKLER, UNSPLASH, CC0 (HTTPS://CREATIVECOMMONS.ORG/PUBLICDOMAIN/ZERO/1.0/)

A new analysis contradicts popular thinking about beliefs in conspiracy theories, suggesting that such beliefs may not have actually increased over time. Joseph Uscinski of the University of Miami, Florida, and colleagues present these findings in the open-access journal PLOS ONE on July 20, 2022.

Belief in a conspiracy theory involves holding the opinion that a small group of people has covertly coordinated to cause a certain event or circumstance, despite a lack of appropriate evidence. In recent years, the perception that beliefs in conspiracy theories have increased has become widespread among the general public, as well as among scholars, journalists, and policymakers, with many blaming social media. However, few studies have examined whether such perceptions actually hold true.

To help clarify whether beliefs in conspiracy theories are increasing, Uscinski and colleagues conducted four different survey analyses. For the first, they investigated whether beliefs in certain conspiracy theories—including theories related to COVID-19 and the Kennedy assassination—have increased among Americans. The second analysis evaluated beliefs in conspiracy theories, such as the idea that human-driven global warming is a hoax, in six European countries. The third analysis addressed Americans’ beliefs in which specific groups are conspiring, and the fourth measured general lines of thought in the U.S. linked to belief in conspiracy theories.

In all four analyses, the researchers found no statistically significant evidence that beliefs in conspiracy theories have increased over time. A greater number of beliefs in specific theories decreased than increased over time, and of those that did increase, none involved the COVID-19 pandemic nor QAnon.

The researchers emphasize the importance of caution in making inferences based in their findings and note that additional research will be needed to confirm the findings and to better understand beliefs in conspiracy theories, such as their psychological underpinnings and how they are promoted.

Nonetheless, these findings suggest that beliefs in conspiracy theories exist at certain baseline levels that may be concerning, and perhaps these levels are only now becoming more apparent to the public.

Dr. Adam Enders adds: “Despite popular claims about America slipping down the conspiracy theory rabbit hole into a state of post-truth, we do not find that conspiracism has increased over time. We examine beliefs in dozens of specific conspiracy theories, perceptions of who is likely to be involved in conspiracy theories, and the general predisposition to interpret events and circumstances as the product of conspiracy theories––in no case do we observe an average increase in conspiracy beliefs.”

Dr. Joseph Uscinski adds: “Some conspiracy theories are gaining in popularity, but many are not. At any given time, perhaps because of political circumstances, some conspiracy theories will be more attractive, but at the same time, many other will recede into history.”

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In your coverage please use this URL to provide access to the freely available article in PLOS ONE: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0270429

Citation: Uscinski J, Enders A, Klofstad C, Seelig M, Drochon H, Premaratne K, et al. (2022) Have beliefs in conspiracy theories increased over time? PLoS ONE 17(7): e0270429. https://doi.org/10.1371/journal.pone.0270429

Author Countries: U.S.A., U.K.

Funding: National Science Foundation Grant #2123635 paid for effort by JU, CK, MS, KP, and MM’s efforts. URL: https://www.nsf.gov/. Portions of the data used in this study was funded by the Leverhulme Trust. Project title: Conspiracy and Democracy URL: https://www.leverhulme.ac.uk/former-schemes/conspiracy-and-democracy. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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JOURNAL

PLoS ONE

DOI

10.1371/journal.pone.0270429 

METHOD OF RESEARCH

Survey

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Have beliefs in conspiracy theories increased over time?

ARTICLE PUBLICATION DATE

20-Jul-2022