Water on ancient Mars

 There's a long-standing question in planetary science about the origin of water on Earth, Mars and other large bodies such as the moon. One hypothesis says that it came from asteroids and comets post-formation. But some planetary researchers think that water might just be one of many substances that occur naturally during the formation of planets. A new analysis of an ancient Martian meteorite adds support for this second hypothesis.

Several years ago, a pair of dark meteorites were discovered in the Sahara Desert. They were dubbed NWA 7034 and NWA 7533, where NWA stands for North West Africa and the number is the order in which meteorites are officially approved by the Meteoritical Society, an international planetary science organization. Analysis showed these meteorites are new types of Martian meteorites and are mixtures of different rock fragments.

The earliest fragments formed on Mars 4.4 billion years ago, making them the oldest known Martian meteorites. Rocks like this are rare and can fetch up to $10,000 per gram. But recently 50 grams of NWA 7533 was acquired for analysis by the international team in which Professor Takashi Mikouchi at the University of Tokyo was participating.

"I study minerals in Martian meteorites to understand how Mars formed and its crust and mantle evolved. This is the first time I have investigated this particular meteorite, nicknamed Black Beauty for its dark color," said Mikouchi. "Our samples of NWA 7533 were subjected to four different kinds of spectroscopic analysis, ways of detecting chemical fingerprints. The results led our team to draw some exciting conclusions."

It's well known to planetary scientists that there has been water on Mars for at least 3.7 billion years. But from the mineral composition of the meteorite, Mikouchi and his team deduced it's likely there was water present much earlier, at around 4.4 billion years ago.

"Igneous clasts, or fragmented rock, in the meteorite are formed from magma and are commonly caused by impacts and oxidation," said Mikouchi. "This oxidation could have occurred if there was water present on or in the Martian crust 4.4 billion years ago during an impact that melted part of the crust. Our analysis also suggests such an impact would have released a lot of hydrogen, which would have contributed to planetary warming at a time when Mars already had a thick insulating atmosphere of carbon dioxide."

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Haunted house researchers investigate the mystery of playing with fear

 Chainsaw-wielding maniacs and brain-munching zombies are common tropes in horror films and haunted houses, which, in normal years, are popular Halloween-season destinations for thrill seekers. But what makes such fearsome experiences so compelling, and why do we actively seek them out in frightful recreational settings?

New research accepted for publication in the journal Psychological Science reveals that horror entertains us most effectively when it triggers a distinct physical response -- measured by changes in heart rate -- but is not so scary that we become overwhelmed. That fine line between fun and an unpleasant experience can vary from person to person.

"By investigating how humans derive pleasure from fear, we find that there seems to be a 'sweet spot' where enjoyment is maximized," said Marc Malmdorf Andersen, a researcher at the Interacting Minds Center at Aarhus University and lead author of the paper. "Our study provides some of the first empirical evidence on the relationship between fear, enjoyment, and physical arousal in recreational forms of fear."

For years, researchers have suspected that physiological arousal, such as a quickening pulse and a release of hormones in the brain, may play a key role in explaining why so many people find horror movies and haunted houses so attractive.

Until now, however, a direct relationship between arousal and enjoyment from these types of activities has not been established. "No prior studies have analyzed this relationship on subjective, behavioral, as well as physiological levels," said Andersen.

To explore this connection, Andersen and his colleagues studied how a group of 110 participants responded to a commercial haunted house attraction in Vejle, Denmark. The researchers fitted each participant with a heart rate monitor, which recorded real-time data as they walked through the attraction. The nearly 50-room haunted house produced an immersive and intimate live-action horror experience. The attraction used a variety of scare tactics to frighten guests, including frequent jump scares, in which zombies or other monstrous abominations suddenly appeared or charged toward the guest.

The researchers also studied the participants in real time through closed-circuit monitors inside the attraction. This enabled the team to make first-hand observations of participants' reactions to the most frightening elements, and, subsequently, to have independent coders analyze participants' behavior and responses. After the experience, participants evaluated their level of fright and enjoyment for each encounter. By comparing these self-reported experiences with the data from the heart rate monitors and surveillance cameras, the researchers were able to compare the fear-related and enjoyment-related elements of the attraction on subjective, behavioral, and physiological levels.

What Is Recreational Fear?

Recreational fear refers to the mixed emotional experience of feeling fear and enjoyment at the same time. Fear is generally considered to be an unpleasant emotion that evolved to protect people from harm. Paradoxically, humans sometimes seek out frightening experiences for purely recreational purposes. "Past studies on recreational fear, however, have not been able to establish a direct relationship between enjoyment and fear," said Andersen.

Studies on fearful responses to media, for example, have mostly been conducted in laboratory settings with relatively weak stimuli, such as short video clips from frightening films. Such experimental setups can sometimes make it difficult to measure physiological arousal because responses may be modest in a laboratory context.

"Conducting our study at a haunted attraction, where participants are screaming with both fear and delight, made this task easier," said Andersen. "It also presented unique challenges, such as the immensely complex logistics associated with conducting empirical studies in a 'messy' real-world context like a haunted house."

Discovering the "Goldilocks Zone"

Plotting the relationship between self-reported fear and enjoyment, the researchers discovered an inverted U-shape trend, revealing an apparent sweet spot for fear where enjoyment is maximized.

"If people are not very scared, they do not enjoy the attraction as much, and the same happens if they are too scared," said Andersen. "Instead, it seems to be the case that a 'just-right' amount of fear is central for maximizing enjoyment."

The data also showed a similar inverted U-shape for the participants' heart rate signatures, suggesting that enjoyment is related to just-right deviations from a person's normal physiological state. However, when fearful encounters trigger large and long-lasting deviations from this normal state, as measured by pulse rates going up and down frequently over a longer period of time, unpleasant sensations often follow.

"This is strikingly similar to what scientists have found to characterize human play," said Andersen. "We know, for instance, that curiosity is often aroused when individuals have their expectations violated to a just-right degree, and several accounts of play stress the importance of just-right doses of uncertainty and surprise for explaining why play feels enjoyable."

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Mothers pass on allergies to offspring

 Mothers can pass allergies to offspring while they are developing in the womb, researchers from the Agency for Science, Technology and Research (A*STAR), KK Women's and Children's Hospital (KKH) and Duke-NUS Medical School in Singapore reported this week in the journal Science.

The study, which employed an animal model conducted according to the National Advisory Committee for Laboratory Animal Research (NACLAR) guidelines, shows that the key antibody responsible for triggering allergic reactions, immunoglobulin E (IgE), can cross the placenta and enter the fetus. When inside the fetus, the antibody binds to fetal mast cells, a type of immune cell that releases chemicals that trigger allergic reactions, from runny noses to asthma. After birth, newborn mice develop allergic reactions to the same type of allergen as their mothers at the time of first exposure -- unlike adult mice, which require two exposures. Studies in the laboratory also showed that maternal IgE can bind to human fetal mast cells, indicating they might cross the placenta in humans in a similar way.

Dr Florent Ginhoux, Senior Principal Investigator at A*STAR's Singapore Immunology Network (SIgN), a senior co-author of the study, said, "There is currently a significant lack of knowledge on mast cells that are present early on in the developing fetus. Here, we discovered that fetal mast cells phenotypically mature through the course of pregnancy, and can be sensitised by IgE of maternal origin that cross the placental barrier. The study suggests that a highly allergic pregnant mother may potentially transfer her IgE to her baby that consequently develop allergic reactions when exposed to the first time to the allergen."

"Allergies begin very early in life," said Associate Professor Ashley St. John, an immunologist at Duke-NUS' Emerging Infectious Diseases Programme and a senior co-author of the study. "Infants experience allergic responses closely linked with the mother's allergic response in ways that cannot only be explained by genetics. This work emphasises one way that allergic responses can pass from the mother to the developing fetus, and shows how allergies can then persist after birth."

As part of the study, following NACLAR guidelines, researchers exposed mice to ragweed pollen, a common allergen, prior to pregnancy. Mice that developed a sensitivity to the pollen had offspring that also showed an allergic reaction to ragweed. The sensitivity is allergen-specific; the offspring did not react to dust mites, another common allergen.

Notably, the transfer of sensitivity appears to fade with time. The newborn mice had allergic reactions when tested at four weeks, but less or none at six weeks.

The experimental studies were backed up with cellular tests and imaging, which showed maternal IgE bound to fetal mast cells, triggering the mast cells to release chemicals in reaction to an allergen, a process called degranulation.

This study further showed that the IgE transfer across the placenta requires the help of another protein, FcRN. Mice with FcRN knocked out lacked maternal IgE attached to their mast cells, and did not develop allergies after birth.

The study findings potentially open new intervention strategies to limit such transfer to minimise the occurrence of neonatal allergies. Currently, between 10 to 30 per cent of the world's population are affected by allergies. This number is set to continue rising and a solution preventing allergies being passed from mother to child could potentially bring those numbers down over time.

"Our research has really exciting findings that may explain the high incidence of early onset atopic dermatitis (eczema) in children of mothers with clinically proven eczema, which parallel findings in our local birth cohort findings," said Professor Jerry Chan, Senior Consultant, Department of Reproductive Medicine at KKH, Senior National Medical Research Council Clinician Scientist, and Vice Chair of Research with the Obstetrics and Gynaecology Academic Clinical Programme at the SingHealth Duke-NUS Academic Medical Centre. "From a clinical point of view, developing a further understanding in placental transfer of IgE, and the mechanism of fetal mast cell activation would be key to developing strategies to reduce the chance of eczema or other allergies from being transferred from mother to baby."

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Positive outlook predicts less memory decline

 

Senior couple on bench

We may wish some memories could last a lifetime, but many physical and emotional factors can negatively impact our ability to retain information throughout life.

A new study published in the journal Psychological Science found that people who feel enthusiastic and cheerful -- what psychologists call "positive affect" -- are less likely to experience memory decline as they age. This result adds to a growing body of research on positive affect's role in healthy aging.

A team of researchers analyzed data from 991 middle-aged and older U.S. adults who participated in a national study conducted at three time periods: between 1995 and 1996, 2004 and 2006, and 2013 and 2014.

In each assessment, participants reported on a range of positive emotions they had experienced during the past 30 days. In the final two assessments, participants also completed tests of memory performance. These tests consisted of recalling words immediately after their presentation and again 15 minutes later.

The researchers examined the association between positive affect and memory decline, accounting for age, gender, education, depression, negative affect, and extraversion.

"Our findings showed that memory declined with age," said Claudia Haase, an associate professor at Northwestern University and senior author on the paper. "However, individuals with higher levels of positive affect had a less steep memory decline over the course of almost a decade," added Emily Hittner, a PhD graduate of Northwestern University and the paper's lead author.

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Touch and taste? It's all in the tentacles

 

Suction cups on octopus tentacles

Octopuses have captured the human imagination for centuries, inspiring sagas of sea monsters from Scandinavian kraken legends to TV's "Voyage to the Bottom of the Sea" and, most recently, Netflix's less-threatening "My Octopus Teacher." With their eight suction-cup covered tentacles, their very appearance is unique, and their ability to use those appendages to touch and taste while foraging further sets them apart.

In fact, scientists have wondered for decades how those arms, or more specifically the suction cups on them, do their work, prompting a number of experiments into the biomechanics. But very few have studied what is happening on a molecular level. In a new report, Harvard researchers got a glimpse into how the nervous system in the octopus' arms (which operate largely independently from its centralized brain) manage this feat.

The work published Thursday in Cell.

The scientists identified a novel family of sensors in the first layer of cells inside the suction cups that have adapted to react and detect molecules that don't dissolve well in water. The research suggests these sensors, called chemotactile receptors, use these molecules to help the animal figure out what it's touching and whether that object is prey.

"We think because the molecules do not solubilize well, they could, for instance, be found on the surface of octopuses' prey and [whatever the animals touch]," said Nicholas Bellono, an assistant professor of molecular and cellular biology and the study's senior author. "So, when the octopus touches a rock versus a crab, now its arm knows, 'OK, I'm touching a crab [because] I know there's not only touch but there's also this sort of taste.'"

In addition, scientists found diversity in what the receptors responded to and the signals they then transmitted to the cell and nervous systems.

"We think that this is important because it could facilitate complexity in what the octopus senses and also how it can process a range of signals using its semi-autonomous arm nervous system to produce complex behaviors," Bellono said.

The scientists believe this research can help uncover similar receptor systems in other cephalopods, the invertebrate family that also includes squids and cuttlefish. The hope is to determine how these systems work on a molecular level and answer some relatively unexplored questions about how these creatures' capabilities evolved to suit their environment.

"Not much is known about marine chemotactile behavior and with this receptor family as a model system, we can now study which signals are important for the animal and how they can be encoded," said Lena van Giesen, a postdoctoral fellow in the Bellono Lab and lead author of the paper. "These insights into protein evolution and signal coding go far beyond just cephalopods."

Along with Giesen, other co-authors from the lab include Peter B. Kilian, an animal technician, and Corey A.H. Allard, a postdoctoral fellow.

"The strategies they have evolved in order to solve problems in their environment are unique to them and that inspires a great deal of interest from both scientists and non-scientists alike," Kilian said. "People are drawn to octopuses and other cephalopods because they are wildly different from most other animals."

The team set out to uncover how the receptors are able to sense chemicals and detect signals in what they touch, like a tentacle around a snail, to help them make choices.

Octopus arms are distinct and complex. About two-thirds of an octopus's neurons are located in their arms. Because the arms operate partially independently from the brain, if one is severed it can still reach for, identify, and grasp items.

The team started by identifying which cells in the suckers actually do the detecting. After isolating and cloning the touch and chemical receptors, they inserted them in frog eggs and in human cell lines to study their function in isolation. Nothing like these receptors exists in frog or human cells, so the cells act essentially like closed vessels for the study of these receptors.

The researchers then exposed those cells to molecules such as extracts from octopus prey and others items to which these receptors are known to react. Some test subjects were water-soluble, like salts, sugars, amino acids; others do not dissolve well and are not typically considered of interest by aquatic animals. Surprisingly, only the poorly soluble molecules activated the receptors.

Researchers then went back to the octopuses in their lab to see whether they too responded to those molecules by putting those same extracts on the floors of their tanks. They found the only odorants the octopuses receptors responded to were a non-dissolving class of naturally occurring chemicals known as terpenoid molecules.

"[The octopus] was highly responsive to only the part of the floor that had the molecule infused," Bellono said. This led the researchers to believe that the receptors they identified pick up on these types of molecules and help the octopus distinguish what it's touching. "With the semi-autonomous nervous system, it can quickly make this decision: 'Do I contract and grab this crab or keep searching?'"

While the study provides a molecular explanation for this aquatic touch-taste sensation in octopuses through their chemotactile receptors, the researchers suggest further study is needed, given that a great number of unknown natural compounds could also stimulate these receptors to mediate complex behaviors.

"We're now trying to look at other natural molecules that these animals might detect," Bellono said.

Read more at Science Daily

Where were Jupiter and Saturn born?

 

Jupiter and Saturn

New work led by Carnegie's Matt Clement reveals the likely original locations of Saturn and Jupiter. These findings refine our understanding of the forces that determined our Solar System's unusual architecture, including the ejection of an additional planet between Saturn and Uranus, ensuring that only small, rocky planets, like Earth, formed inward of Jupiter.

In its youth, our Sun was surrounded by a rotating disk of gas and dust from which the planets were born. The orbits of early formed planets were thought to be initially close-packed and circular, but gravitational interactions between the larger objects perturbed the arrangement and caused the baby giant planets to rapidly reshuffle, creating the configuration we see today.

"We now know that there are thousands of planetary systems in our Milky Way galaxy alone," Clement said. "But it turns out that the arrangement of planets in our own Solar System is highly unusual, so we are using models to reverse engineer and replicate its formative processes. This is a bit like trying to figure out what happened in a car crash after the fact -- how fast were the cars going, in what directions, and so on."

Clement and his co-authors -- Carnegie's John Chambers, Sean Raymond of the University of Bordeaux, Nathan Kaib of University of Oklahoma, Rogerio Deienno of the Southwest Research Institute, and André Izidoro of Rice University -- conducted 6,000 simulations of our Solar System's evolution, revealing an unexpected detail about Jupiter and Saturn's original relationship.

Jupiter in its infancy was thought to orbit the Sun three times for every two orbits that Saturn completed. But this arrangement is not able to satisfactorily explain the configuration of the giant planets that we see today. The team's models showed that a ratio of two Jupiter orbits to one Saturnian orbit more consistently produced results that look like our familiar planetary architecture.

"This indicates that while our Solar System is a bit of an oddball, it wasn't always the case," explained Clement, who is presenting the team's work at the American Astronomical Society's Division for Planetary Sciences virtual meeting today. "What's more, now that we've established the effectiveness of this model, we can use it to help us look at the formation of the terrestrial planets, including our own, and to perhaps inform our ability to look for similar systems elsewhere that could have the potential to host life."

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Measuring the expansion of the universe: Researchers focus on velocity

 Ever since the astronomer Edwin Hubble demonstrated that the further apart two galaxies are, the faster they move away from each other, researchers have measured the expansion rate of the Universe (the Hubble constant) and the history of this expansion. Recently, a new puzzle has emerged, as there seems to be a discrepancy between measurements of this expansion using radiation in the early Universe and using nearby objects. Researchers from the Cosmic Dawn Center, at the Niels Bohr Institute, University of Copenhagen, have now contributed to this debate by focusing on velocity measurements. The result has been published in Astrophysical Journal.

The researchers at the Cosmic Dawn Center found that the measurements of velocity used for determining the expansion rate of the Universe may not be reliable. As stated in the publication, this doesn't resolve the discrepancies, but rather hints at an additional inconsistency in the composition of the Universe.

Measuring the expansion rate of the Universe

Currently, astronomers measure the expansion of the Universe using two very different techniques. One is based on measuring the relationship between distance and velocity of nearby galaxies, while the other stems from studying the background radiation from the very early universe. Surprisingly, these two approaches currently find different expansion rates. If this discrepancy is real, a new and rather dramatic reinterpretation of the development of the Universe will be the consequence. However, it is also possible that the difference in the Hubble constant could be from incorrect measurements. It is difficult to measure distances in the Universe, so many studies have focused on improving and recalibrating distance measurements. But in spite of this, over the last 4 years the disagreement has not been resolved.

The velocity of the remote galaxies is easy to measure -- or so we thought

In the recent scientific article, the researchers from the Cosmic Dawn Center now attempt to shine light on a related problem: the measurement of velocity. Depending on the velocity with which a remote object moves away from us, its light shifts to redder colors. With this so-called redshift it is possible to measure the velocity from a spectrum of a remote galaxy. Unlike measurements of distance, until now it was assumed that velocities were relatively easy to measure.

However, when the researchers recently examined distance and velocity measurements from more than 1000 supernovae (exploding stars) collected during the last 25 years, they found a surprising discrepancy in their results. Albert Sneppen, Masters student at the Niels Bohr Institute explains: "We've always believed that measuring velocities was fairly straightforward and precise, but it turns out that we are actually dealing with two types of redshifts."

The first type, measuring the velocity with which the host-galaxy moves away from us, is considered the most reliable. The other type of redshift measures instead the velocity of matter ejected from the exploding star inside the galaxy. Or, more precisely, the matter from the supernova moving towards us with a few percent of the velocity of light (illustration 1). After compensating for this extra movement the redshift -- and velocity -- of the host galaxy can be determined. But this compensation requires a precise model for the explosion. The researchers were able to determine that the results from these two different techniques result in two different expansion histories for the Universe, and therefore two different compositions as well.

Are things "broken in an interesting way?"

So, does this mean that the measurements of the early Universe and newer measurements are ultimately a question of imprecise measurements of velocity? Probably not, says Bidisha Sen, one the authors of the article. "Even if we only use the more reliable redshifts, the supernova measurements not only continue to disagree with the Hubble constant measured from the early Universe -- they also hint at a more general discrepancy regarding the composition of the Universe," she says.

Associate professor at the Niels Bohr Institute Charles Steinhardt, is intrigued by these new results. "If we are actually dealing with two disagreements, it means that our current model would be "broken in an interesting way," he says. "In order to solve two problems, one regarding the composition of the Universe and one regarding the expansion rate of the Universe, rather different physical explanations are required than if we only want to explain a single discrepancy in the expansion rate."

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Study helps explain why motivation to learn declines with age

 As people age, they often lose their motivation to learn new things or engage in everyday activities. In a study of mice, MIT neuroscientists have now identified a brain circuit that is critical for maintaining this kind of motivation.

This circuit is particularly important for learning to make decisions that require evaluating the cost and reward that come with a particular action. The researchers showed that they could boost older mice's motivation to engage in this type of learning by reactivating this circuit, and they could also decrease motivation by suppressing the circuit.

"As we age, it's harder to have a get-up-and-go attitude toward things," says Ann Graybiel, an Institute Professor at MIT and member of the McGovern Institute for Brain Research. "This get-up-and-go, or engagement, is important for our social well-being and for learning -- it's tough to learn if you aren't attending and engaged."

Graybiel is the senior author of the study, which appears today in Cell. The paper's lead authors are Alexander Friedman, a former MIT research scientist who is now an assistant professor at the University of Texas at El Paso, and Emily Hueske, an MIT research scientist.

Evaluating cost and benefit

The striatum is part of the basal ganglia -- a collection of brain centers linked to habit formation, control of voluntary movement, emotion, and addiction. For several decades, Graybiel's lab has been studying clusters of cells called striosomes, which are distributed throughout the striatum. Graybiel discovered striosomes many years ago, but their function had remained mysterious, in part because they are so small and deep within the brain that it is difficult to image them with functional magnetic resonance imaging (fMRI).

In recent years, Friedman, Graybiel, and colleagues including MIT research fellow Ken-ichi Amemori have discovered that striosomes play an important role in a type of decision-making known as approach-avoidance conflict. These decisions involve choosing whether to take the good with the bad -- or to avoid both -- when given options that have both positive and negative elements. An example of this kind of decision is having to choose whether to take a job that pays more but forces a move away from family and friends. Such decisions often provoke great anxiety.

In a related study, Graybiel's lab found that striosomes connect to cells of the substantia nigra, one of the brain's major dopamine-producing centers. These studies led the researchers to hypothesize that striosomes may be acting as a gatekeeper that absorbs sensory and emotional information coming from the cortex and integrates it to produce a decision on how to act. These actions can then be invigorated by the dopamine-producing cells.

The researchers later discovered that chronic stress has a major impact on this circuit and on this kind of emotional decision-making. In a 2017 study performed in rats and mice, they showed that stressed animals were far more likely to choose high-risk, high-payoff options, but that they could block this effect by manipulating the circuit.

In the new Cell study, the researchers set out to investigate what happens in striosomes as mice learn how to make these kinds of decisions. To do that, they measured and analyzed the activity of striosomes as mice learned to choose between positive and negative outcomes.

During the experiments, the mice heard two different tones, one of which was accompanied by a reward (sugar water), and another that was paired with a mildly aversive stimulus (bright light). The mice gradually learned that if they licked a spout more when they heard the first tone, they would get more of the sugar water, and if they licked less during the second, the light would not be as bright.

Learning to perform this kind of task requires assigning value to each cost and each reward. The researchers found that as the mice learned the task, striosomes showed higher activity than other parts of the striatum, and that this activity correlated with the mice's behavioral responses to both of the tones. This suggests that striosomes could be critical for assigning subjective value to a particular outcome.

"In order to survive, in order to do whatever you are doing, you constantly need to be able to learn. You need to learn what is good for you, and what is bad for you," Friedman says.

"A person, or this case a mouse, may value a reward so highly that the risk of experiencing a possible cost is overwhelmed, while another may wish to avoid the cost to the exclusion of all rewards. And these may result in reward-driven learning in some and cost-driven learning in others," Hueske says.

The researchers found that inhibitory neurons that relay signals from the prefrontal cortex help striosomes to enhance their signal-to-noise ratio, which helps to generate the strong signals that are seen when the mice evaluate a high-cost or high-reward option.

Loss of motivation

Next, the researchers found that in older mice (between 13 and 21 months, roughly equivalent to people in their 60s and older), the mice's engagement in learning this type of cost-benefit analysis went down. At the same time, their striosomal activity declined compared to that of younger mice. The researchers found a similar loss of motivation in a mouse model of Huntington's disease, a neurodegenerative disorder that affects the striatum and its striosomes.

When the researchers used genetically targeted drugs to boost activity in the striosomes, they found that the mice became more engaged in performance of the task. Conversely, suppressing striosomal activity led to disengagement.

In addition to normal age-related decline, many mental health disorders can skew the ability to evaluate the costs and rewards of an action, from anxiety and depression to conditions such as PTSD. For example, a depressed person may undervalue potentially rewarding experiences, while someone suffering from addiction may overvalue drugs but undervalue things like their job or their family.

The researchers are now working on possible drug treatments that could stimulate this circuit, and they suggest that training patients to enhance activity in this circuit through biofeedback could offer another potential way to improve their cost-benefit evaluations.

"If you could pinpoint a mechanism which is underlying the subjective evaluation of reward and cost, and use a modern technique that could manipulate it, either psychiatrically or with biofeedback, patients may be able to activate their circuits correctly," Friedman says.

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Average body temperature among healthy adults declined over the past two decades

 In the nearly two centuries since German physician Carl Wunderlich established 98.6°F as the standard "normal" body temperature, it has been used by parents and doctors alike as the measure by which fevers -- and often the severity of illness -- have been assessed.

Over time, however, and in more recent years, lower body temperatures have been widely reported in healthy adults. A 2017 study among 35,000 adults in the United Kingdom found average body temperature to be lower (97.9°F), and a 2019 study showed that the normal body temperature in Americans (those in Palo Alto, California, anyway) is about 97.5°F.

A multinational team of physicians, anthropologists and local researchers led by Michael Gurven, UC Santa Barbara professor of anthropology and chair of the campus's Integrative Anthropological Sciences Unit, and Thomas Kraft, a postdoctoral researcher in the same department, have found a similar decrease among the Tsimane, an indigenous population of forager-horticulturists in the Bolivian Amazon. In the 16 years since Gurven, co-director of the Tsimane Health and Life History Project, and fellow researchers have been studying the population, they have observed a rapid decline in average body temperature -- 0.09°F per year, such that today Tsimane body temperatures are roughly 97.7°F.

"In less than two decades we're seeing about the same level of decline as that observed in the U.S. over approximately two centuries," said Gurven. Their analysis is based on a large sample of 18,000 observations of almost 5,500 adults, and adjust for multiple other factors that might affect body temperature, such as ambient temperature and body mass.

The anthropologists' research appears in the journal Sciences Advances.

"The provocative study showing declines in normal body temperature in the U.S. since the time of the Civil War was conducted in a single population and couldn't explain why the decline happened," said Gurven. "But it was clear that something about human physiology could have changed. One leading hypothesis is that we've experienced fewer infections over time due to improved hygiene, clean water, vaccinations and medical treatment. In our study, we were able to test that idea directly. We have information on clinical diagnoses and biomarkers of infection and inflammation at the time each patient was seen.

While some infections were associated with higher body temperature, adjusting for these did not account for the steep decline in body temperature over time, Gurven noted. "And we used the same type of thermometer for most of the study, so it's not due to changes in instrumentation," he said.

Added Kraft, "No matter how we did the analysis, the decline was still there. Even when we restricted analysis to the <10% of adults who were diagnosed by physicians as completely healthy, we still observed the same decline in body temperature over time."

A key question, then, is why body temperatures have declined over time both for Americans and Tsimane. Extensive data available from the team's long-term research in Bolivia addresses some possibilities. "Declines might be due to the rise of modern health care and lower rates of lingering mild infections now as compared to the past," Gurven explained. "But while health has generally improved over the past two decades, infections are still widespread in rural Bolivia. Our results suggest that reduced infection alone can't explain the observed body temperature declines."

It could be that people are in better condition, so their bodies might be working less to fight infection, he continued. Or greater access to antibiotics and other treatments means the duration of infection is shorter now than in the past. Consistent with that argument, Gurven said, "We found that having a respiratory infection in the early period of the study led to having a higher body temperature than having the same respiratory infection more recently."

It's also possible that greater use of anti-inflammatory drugs like ibuprofen may reduce inflammation, though the researchers found that the temporal decline in body temperature remained even after their analyses accounted for biomarkers of inflammation.

"Another possibility is that our bodies don't have to work as hard to regulate internal temperature because of air conditioning in the summer and heating in the winter," Kraft said. "While Tsimane body temperatures do change with time of year and weather patterns, the Tsimane still do not use any advanced technology for helping to regulate their body temperature. They do, however, have more access to clothes and blankets."

The researchers were initially surprised to find no single "magic bullet" that could explain the decline in body temperature. "It's likely a combination of factors -- all pointing to improved conditions," Gurven said.

According to Gurven, the finding of lower-than-expected body temperatures in the U.S., and the decline over time, had a lot of people scratching their heads. Was it a fluke? In this study, Gurven and his team confirm that body temperatures below 98.6°F are found in places outside the U.S. and the U.K. "The area of Bolivia where the Tsimane live is rural and tropical with minimal public health infrastructure," he noted. "Our study also gives the first indication that body temperatures have declined even in this tropical environment, where infections still account for much morbidity and mortality."

As a vital sign, temperature is an indicator of what's occurring physiologically in the body, much like a metabolic thermostat. "One thing we've known for a while is that there is no universal 'normal' body temperature for everyone at all times, so I doubt our findings will affect how clinicians use body temperature readings in practice" said Gurven. Despite the fixation on 98.6°F, most clinicians recognize that 'normal' temperatures have a range. Throughout the day, body temperature can vary by as much as 1°F, from its lowest in the early morning, to its highest in the late afternoon. It also varies across the menstrual cycle and following physical activity and tends to decrease as we age.

Read more at Science Daily

Denisovan DNA in the genome of early East Asians

 Researchers analyzed the genome of the oldest human fossil found in Mongolia to date and show that the 34,000-year-old woman inherited around 25 percent of her DNA from western Eurasians, demonstrating that people moved across the Eurasian continent shortly after it had first been settled by the ancestors of present-day populations. This individual and a 40,000-year-old individual from China also carried DNA from Denisovans, an extinct form of hominins that inhabited Asia before modern humans arrived.

In 2006, miners discovered a hominin skullcap with peculiar morphological features in the Salkhit Valley of the Norovlin county in eastern Mongolia. It was initially referred to as Mongolanthropus and thought to be a Neandertal or even a Homo erectus. The remains of the "Salkhit" individual represent the only Pleistocene hominin fossil found in the country.

Ancient DNA extracted from the skullcap shows that it belonged to a female modern human who lived 34,000 ago and was more related to Asians than to Europeans. Comparisons to the only other early East Asian individual genetically studied to date, a 40,000-year-old male from Tianyuan Cave outside Beijing (China), show that the two individuals are related to each other. However, they differ insofar that a quarter of the ancestry of the Salkhit individual derived from western Eurasians, probably via admixture with ancient Siberians.

Migration and interaction

"This is direct evidence that modern human communities in East Asia were already quite cosmopolitan earlier than 34,000 years ago," says Diyendo Massilani, lead author of the study and researcher at the Max-Planck Institute for Evolutionary Anthropology. "This rare specimen shows that migration and interactions among populations across Eurasia happened frequently already some 35,000 years ago."

The researchers used a new method developed at the Max-Planck Institute for Evolutionary Anthropology to find segments of DNA from extinct hominins in the Salkhit and Tianyuan genomes. They found that the two genomes contain not only Neandertal DNA but also DNA from Denisovans, an elusive Asian relative of Neandertals. "It is fascinating to see that the ancestors of the oldest humans in East Asia from whom we have been able to obtain genetic data had already mixed with Denisovans, an extinct form of hominins that has contributed ancestry to present-day populations in Asia and Oceania," says Byambaa Gunchinsuren, a researcher at the Institute of Archaeology of the Mongolian Academy of Sciences. "This is direct evidence that Denisovans and modern humans had met and mixed more than 40,000 years ago."

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