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Comment by Dr. Krishna Kumari Challa 8 minutes ago

in this case, the probability of a species successfully adapting multiplies with every condition that it meets. And it turns out that this pattern can be described mathematically as a very simple, bell-shaped curve. Such a curve essentially describes what fraction of the world's animals can adapt at given rates, from the slowest to the fastest adapters, and how this fraction changes nonlinearly with the rate of adaptation. This curve generally shows that most animal groups can adapt at intermediate rates, while fewer animal groups adapt at the slowest and fastest rates.

After establishing this general pattern of adaptation rates, the researchers looked to see how this pattern compares with recorded rates of environmental change, and how these two rates match, or don't match, at times of mass extinction.

To do so, they considered paleontological and geochemical data from 27 episodes over the last 450 million years in which the carbon cycle experienced significant change—a measure that is generally understood to reflect global environmental change. They then compared rates of environmental change with the fraction of animal groups that went extinct during each episode—numbers that were established previously in a well-regarded study by paleobiologist John Alroy.
In the end, researchers observed that, for almost every mass extinction event in the last 450 million years, there was a mismatch in the rates at which the environment changed and at which animals could adapt; mass extinctions occurred when a significant fraction of animals could not adapt fast enough to match the changing environment. Their results confirm that the rate-mismatch hypothesis applies at the global scale.
Moreover, this mismatch in rates could predict the severity of extinction events, or the fraction of animal life that went extinct given the rate at which the environment changed.

In the case of the end-Permian extinction, it's likely that the rapid acidification of the ocean outpaced organisms' ability to evolve adequate protections, leading to the extinction of more than 80% of the world's marine species.

The team's work focuses on applying the new model to past extinction events. But the work could also provide a framework for understanding modern extinction risk.
Carbon dioxide levels in the ocean are increasing today at a rate which, when appropriately re-scaled, is similar to rates of carbon-cycle change that are just lower than those associated with major extinction events in the past.
It suggests that modern environmental change may be approaching rates beyond which adaptation becomes increasingly difficult.

Daniel H. Rothman et al, Relating Rates of Global Change, Evolutionary Adaptation, and Extinction, Physical Review Letters (2026). DOI: 10.1103/62jn-xgqy

Part 2

Comment by Dr. Krishna Kumari Challa 10 minutes ago

What happens when environmental change outpaces life's ability to adapt?

When an animal's environment changes faster than the animal can adapt, its chances of survival can flatline. The same is true for populations and even entire species. Now, scientists have found that this connection between evolutionary adaptation and the pace of environmental change holds up at the global scale as well—and can determine life's susceptibility to mass extinction. The researchers have developed a theoretical model of this phenomenon, which they present in a paper published recently in Physical Review Letters.

A mathematical model links mass extinction severity to a mismatch between rates of global environmental change and biological adaptation. Using carbon-cycle proxies and extinction data from 27 events over 450 Myr, mass die-offs occur when environmental change exceeds most taxa’s adaptive capacity. Modern CO₂-driven change approaches these critical rate thresholds.

The team compared the model with available data from past major mass extinctions, including how fast the global environment changed at the time of each event. The model successfully predicted the severity of most mass extinctions in Earth's history, or the fraction of life that was unable to adapt and therefore went extinct.

Interestingly, the researchers found that the range of adaptation rates across animal groups is broadly similar to the range of rates at which the environment can change.
What we're beginning to see is a certain level of organization, and ways in which life behaves that are consistent with the ways in which the environment behaves.
It may be that life has evolved so that its range of adaptabilities matches the range of stresses that it meets.
For their new study, the researchers looked to test the rate-mismatch hypothesis at the global scale. They wanted to see whether mass extinction events in history could be explained by a mismatch between the rate of global environmental change and the rate at which life around the world can adapt.

To do so, at least in theory, they would have to compare two sources of data: the rates at which the global environment has changed over time and the rates at which different groups of organisms adapt to environmental change. The first can be found in geological records, which scientists have used extensively to infer how Earth's climate changed through history. The second, however, is almost impossible to record.
It is generally understood in evolutionary theory that a species can successfully adapt only when multiple conditions are met. For instance, there must be variation in the population. These variations must be heritable, some variations must enable an organism to adapt better than others, and the organisms that adapt better should leave more offspring. If all these conditions are met, the entire species should be able to adapt to a given environmental change. However, if any one condition fails, the population will go extinct.
Part 1

Comment by Dr. Krishna Kumari Challa 25 minutes ago

Did gravitational tides cause Earth's extinctions?
The article discusses a hypothesis that close passages of planetary-mass or dwarf-planet objects could generate strong gravitational tides, triggering giant tsunamis, enhanced volcanism, climate shifts, and redirected impactors, collectively driving some mass extinctions over the past 600 Myr. Correlations with geological and orbital anomalies are noted, but mass, frequency, and detailed evidence for such flybys remain highly uncertain.

Daniele Fargion, Mass Extinctions by Gravitational Tides, arXiv (2026). DOI: 10.48550/arxiv.2606.17105

Comment by Dr. Krishna Kumari Challa 42 minutes ago

To find this fingerprint, the team turned to an unsupervised deep learning approach—one that could extract hidden structural information from the data without any predefined assumptions about what the two structures should look like.

It is practically impossible for humans to intuitively guess or manually construct such complex, nonlinear, and nearly orthogonal physical parameters.
so the researchers took AIs help.
By using AI the researchers effectively rotated their viewing angle of the data, searching for the configuration at which the two structures—if they existed—would reveal themselves most clearly.
When the model found the optimal configuration, two distinct clusters emerged, suggesting two local structures: Structure A, denser and more disordered, and Structure B, less dense and more ordered. The simulations found these patterns across a broad range of temperatures and pressures, including some close to room-temperature conditions.
But the study revealed something beyond support for the existence of the two structures. The way Structure A and Structure B interconvert depends on where the system sits in the phase diagram. In the high-density liquid phase, the interconversion proceeds via an "upper semi-loop" pathway through a single transition state. In the low-density liquid phase, it follows a different "lower semi-loop" pathway through a different transition state.

Near the liquid-liquid phase boundary, where the two liquid phases compete most intensely, these two pathways combine into a complex three-dimensional "full-loop" reaction pathway involving three transition states. As the system moves away from the boundary and one phase begins to dominate, this full loop degenerates back into a simpler single-pathway semi-loop.

The transformation between Structure A and Structure B is not a simple 'back-and-forth' process. The interconversion pathways of the two structures are different under different states of water. This microscopic dynamic process is extremely difficult to identify using traditional theoretical methods.
The findings provide strong molecular-level evidence for the two-state model of water, with the bimodal feature in the data offering a structural signature of the two distinct local states.

Liwen Li et al, Evidence for the generic existence of two local structures in liquid water, Nature Physics (2026). DOI: 10.1038/s41567-026-03301-8.

Part 2

Comment by Dr. Krishna Kumari Challa 47 minutes ago

Scientists find molecular-level evidence for two structures in liquid water

A study published in Nature Physics provides new molecular-level evidence from simulations that liquid water is not a single uniform substance, but a constantly shifting mixture of two distinct microscopic structures.
The idea that water might exist in two distinct structural states is not new. For decades, scientists have theorized that liquid water is composed of two interconvertible local structures—one denser and more disordered, the other less dense and more ordered.

This "two-state model" has been invoked to explain water's many anomalous properties, including why it becomes easier to compress as it cools and why it reaches maximum density at 4°C (39°F) rather than at its freezing point. But the model has remained controversial because direct molecular-level evidence for the two structures has been elusive.
Central to the two-state model is a hypothesized phenomenon known as the liquid-liquid phase transition (LLPT). The idea is that in the deeply supercooled regime, water splits into two macroscopically distinct liquid phases: a high-density liquid and a low-density liquid.
The boundary between them is thought to terminate at a "second critical point." This deeply supercooled region is so hard to study experimentally because water crystallizes rapidly. Much of the evidence for the LLPT has therefore come from computational studies.

Previously, a 2025 Nature Physics study made progress by using a deep neural network to map the location of this critical point.

"According to the two-state hypothesis, liquid water can be viewed as a mixture of two distinct structures, A and B. But no one has ever seen a genuine 'pure A' or 'pure B' liquid water. Indeed, due to the lack of direct molecular-level evidence, this model has been a subject of debate.
The problem is not just experimental, according to the researchers. Even in simulations, traditional methods that measure local density and energy differences between molecules failed to cleanly separate the two structures. What was needed was a way to let the data reveal the hidden molecular fingerprint of each structure—without any human assumptions about what that fingerprint should look like.
Part 1

Comment by Dr. Krishna Kumari Challa 51 minutes ago

The universe should look the same in all directions at large scales, but DESI data suggest otherwise

Earlier this year, the Dark Energy Spectroscopic Instrument (DESI) completed observations that mapped 47 million galaxies across 11 billion light-years, allowing astronomers to better evaluate the large-scale structure of the visible universe. After studying these data, astronomers say the universe may not look the same in all directions. Their results, published in Nature, contradict a fundamental assumption in modern cosmology.
At the scale of a single galaxy or local groups of galaxies, the universe clearly appears to be anisotropic, meaning the structure is different depending on which direction you look. In one direction, there may be more void space, while another direction may have a cluster of galaxies.

However, the cosmological principle says that at larger scales, the universe consists of matter that is more or less distributed evenly in all directions. This is based on the Copernican principle, which states that there should be no "special observers" in the universe, meaning that at large scales, the universe should look the same from anywhere else in the universe.

For example, if you imagine the universe as a piece of cloth and zoom in to the scale of the individual fibers, you can clearly see areas of empty space and filament-like fibers that connect to make a larger structure. Yet when you zoom out to much larger scales, the cloth appears to be the same everywhere, with evenly distributed materials.
Research focusing on cosmic background radiation has provided some support for the cosmological principle, but other studies have shown that anisotropic structure still exists at scales of tens to hundreds of megaparsecs. However, the statistical significance of these studies is uncertain.
The authors of the new study say that past anisotropy probes tested for preferred directions instead of evaluating more general directional structure.
They found that galaxy samples from DESI show persistent anisotropic structure in galaxy distribution out to roughly gigaparsec scales, meaning galaxies were clumping together more than they should at scales far larger than those previously examined. Taking previous studies suggesting anisotropy at megaparsec scales as an example, this study indicates anisotropy still exists at scales 1,000 times larger.

"These results provide direct evidence that directional coherence persists to larger scales than predicted in the standard framework, challenging the assumption of large-scale isotropy," the study authors write.

Francesco Sylos Labini et al, Detection of anisotropic cosmic structures on a gigaparsec scale, Nature (2026). DOI: 10.1038/s41586-026-10702-5

Comment by Dr. Krishna Kumari Challa 59 minutes ago

Poor metabolic health can age the brain even in young people, finds new large-scale study
Two people of very different ages can have a similar level of biological aging in their brains. Such an occurrence is possible because aging and metabolic health follow two distinct pathways that influence brain health. While it is known that the brain changes as we get older, a recent study analyzing more than 3,000 brain scans found that metabolic issues affect the brain through a different biological pathway than aging does.
The researchers found that the two axes operate independently of one another, meaning a person can be relatively young yet experience brain changes associated with poor metabolic health. These changes, driven by metabolic factors, were also linked to real-world cognitive performance.

People with poorer metabolic health generally struggled more with tasks that required cognitive flexibility, or the ability to shift between competing demands. The association was strongest in females.

The aging axis affects the brain by eroding its structural integrity. This includes thinning of the brain's outer layer and vascular dysfunction, which slows the flow of blood through the brain's vessels. The metabolic axis works differently. Instead of one main driver, it has an army of factors, including body weight, blood pressure and cholesterol, all acting together.

Their shared effect is a drop in cerebral perfusion, that is, less blood actually reaching the brain.

Asa Farahani et al, Aging and metabolism contribute separately to brain–body health, PLOS Biology (2026). DOI: 10.1371/journal.pbio.3003856

Comment by Dr. Krishna Kumari Challa 1 hour ago

A species of gut bacteria could ease anxiety and diarrhea-predominant IBS

Irritable bowel syndrome (IBS) is a condition characterized by abdominal pain, bloating and changes in bowel movements, estimated to affect between 10% and 15% of people worldwide. Past studies suggest that in many cases this condition is accompanied by anxiety, an emotional state marked by worry, fear and/or overthinking about specific life events.
While IBS and anxiety are known to often occur together, the biological processes linking the two have not yet been fully elucidated. One possibility is that bacteria and other microorganisms living in the digestive tract, broadly referred to as gut microbiota, contribute to these biological processes.
Researchers carried out a study aimed at shedding more light on the biological mechanisms linking a type of IBS called diarrhea-predominant IBS (IBS-D), which is associated with frequent loose stools, with anxiety.

Their paper, published in Translational Psychiatry, suggests that a species of gut-inhabiting bacteria called Phocaeicola vulgatus could contribute to easing anxiety associated with IBS-D.
The researchers also carried out a series of genetic analyses on their mouse model of IBS to further explore the effects of the Phocaeicola vulgatus bacteria. The results of these analyses confirmed that the bacteria protected the mouse brain from anxiety.

Finally, giving live Phocaeicola vulgatus to mice eased anxiety by calming brain inflammation and repairing damaged neurons in the amygdala.

Jiacheng Wu et al, Phocaeicola vulgatus improves anxiety-like behavior by ameliorating amygdala neuroinflammation and the neurite impairment in IBS, Translational Psychiatry (2026). DOI: 10.1038/s41398-026-04142-y.

Comment by Dr. Krishna Kumari Challa yesterday

Why pollution affects some asthma patients more than others

For many people with asthma, air-quality advisories are harbingers of worsening symptoms. But the extent to which pollution exacerbates asthma varies widely from person to person.
In a study published in eBioMedicine, researchers identified biological pathways that begin to uncover this mystery, showing how air-pollution exposure interacts with a person's genes.

The study—which is among the largest and most comprehensive of its kind to date—could eventually lead to new avenues for asthma drug development, as well as potential new biomarkers and public health interventions targeted to those who are most vulnerable to pollution-exacerbated asthma.
Asthma severity responses to PM2.5 vary due to genetic differences in oxidative stress–related pathways. Whole-genome, exposure, and airway transcriptomic data identified variants in seven genes, including OXSR1, PXDN, and TPO, that alter pollution-induced RNA responses and are associated with lower lung function. These pathways suggest potential targets for precision diagnostics and interventions.

Using data from nearly 1,000 adults with asthma the analysis included a combination of whole-genome sequencing, air-pollution exposure data and gene-expression profiling. Among the thousands of genes in the human genome, the team focused on about 450 genes that control oxidative stress, a process in which highly reactive molecules can damage cells and tissues.
Those stresses on cells can translate into serious physiologic effects, like worsening lung function or asthma exacerbations.
The team focused on how these genes interacted with the environmental stress of exposure to fine particulate matter known as PM2.5. These microscopic particles, with a diameter less than that of a human hair (less than 2.5 microns), are small enough to penetrate deep into the lungs and are widely considered one of the most harmful components of air pollution.
A clear relationship emerged.

In these individuals who were living with asthma, the higher their exposure to this particulate matter, the lower their lung function overall.
The researchers found that the most vulnerable patients carried variants in seven oxidative stress–related genes that shape how the body responds to cellular damage from pollution. These genetic variants appear to influence how airway cells respond to the PM2.5 exposure, with some variants enhancing protection from PM2.5, while others appear to worsen the damage.

Individuals with less common variants in two specific genes, called OXSR1 and PXDN, had disproportionately worse lung function due to lower protective RNA responses to pollution. Those with a specific variant in another gene, called TPO, had worse lung function as well, but for them, it was due to stronger RNA responses.

The molecular pathways described in the study could point to targets for new therapies—and open the door to much more.

A cross-sectional study of oxidative stress pathway genotypes and their interactions with environmental pollutant levels identifies associations with gene expression and lung function, eBioMedicine (2026). DOI: 10.1016/j.ebiom.2026.106334

Comment by Dr. Krishna Kumari Challa yesterday

Uneven cerebellum aging may partly explain why some older adults stay mentally sharp

The name "cerebellum" comes from Latin and means "little brain." While it is smaller than the rest of the brain, it contains most of the brain's neurons and coordinates a variety of functions and processes in the brain and body. These include balance, posture and fine motor skills like typing or writing.

Scientists may have discovered a new role for the cerebellum, the part of the brain that sits at the base of the skull. A new paper published in the journal Nature Neuroscience reports that different parts of the cerebellum change at different rates with age, which may be linked to differences in cognitive abilities and memory in later life. This may help explain why some people stay sharper as they get older.
The team analyzed brain scans and cognitive test scores from more than 700 healthy U.S. individuals whose data had been collected as part of the Human Connectome Project. Then they mapped out 11 separate sections on the digital scans and calculated how the volume of each region changed with age.

The scientists discovered that the cerebellum does not age evenly. Regions at the back, which are more connected to higher-order thinking networks, show faster shrinking than front regions involved in basic movement.
"We show a spatially heterogeneous pattern of aging in which specific association and motor-related regions show steeper relationships with age than other lobules," the authors wrote in their paper.

The data also revealed that people with a larger cerebellum scored higher on memory and thinking tests as they aged than people with a smaller cerebellum.

The research team saw a similar trend in a pool of about 47,000 adults in the UK Biobank and Alzheimer's Disease Neuroimaging Initiative. However, in people with Alzheimer's, it appears that support from the cerebellum has its limits as the disease progresses. "This supports a threshold-reserve model, in which the cerebellum helps sustain cognition until pathology becomes widespread."

The researchers cannot say for certain whether a larger cerebellum directly causes better cognition in old age. They have shown a link or association, not a true cause-and-effect relationship. Also, their findings might not apply to everyone globally because most of the study data came from white individuals with high levels of education.

Federico d'Oleire Uquillas et al, Cerebellar aging is spatially heterogeneous and supports cognitive resilience in later life, Nature Neuroscience (2026). DOI: 10.1038/s41593-026-02289-x

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