Comment

Comment by Dr. Krishna Kumari Challa on September 10, 2026 at 10:18am

"Therefore, we expect greater risk of obstructed labor, likely cephalopelvic disproportion, with male offspring in several taxa, but it has not yet directly been shown. We cautiously interpret this as support for the 'costly son' hypothesis: male offspring disproportionately contribute to fetopelvic disproportion and obstructed labor owing to their larger average size at birth."

The researchers also point out that the results identify a small average shift in risk for male births, not a prediction for any individual pregnancy. Because this is a comparative review and analysis, it doesn't prove that fetal sex directly causes difficult birth, but it does provide a testable prediction.
Evolutionarily speaking, larger sons often have more offspring because of male-male competition, and thus more grandchildren for the mother, ultimately meaning reproductive "success." The Trivers–Willard hypothesis used this argument to explain why mothers might be more likely to produce sons or daughters, depending on their physical condition. The mother expends more energy on large male babies, and on male babies in general. This increases birth risk but also increases the chance of reproductive success later on.

The study authors explain, "In humans, male fetal sex imposes a double burden on mothers, combining increased obstetric risk with elevated metabolic investment. Mothers of sons expend more energy during pregnancy and lactation, and this higher energetic investment contributes to enhanced fetal growth and larger birth size. In turn, this increased size elevates the risk of obstructed labor and adverse birth outcomes."

The new study does not find that mothers are more or less likely to produce sons or daughters, but the researchers do say that younger mothers seem to produce smaller newborns to partition energetic resources, regardless of sex. They also say it remains unknown whether females can adaptively adjust offspring sex to mitigate obstetric risk. Future work could systematically test whether younger or first-time mothers adjust offspring sex ratios or mainly produce smaller babies.

Nicole D. S. Grunstra et al, The "costly son" hypothesis: Sons exacerbate obstetrical dilemmas in humans and other mammals, The Anatomical Record (2026). DOI: 10.1002/ar.70331

Part 2

Comment by Dr. Krishna Kumari Challa on September 10, 2026 at 10:16am

The 'costly son' hypothesis: Why bigger sons may make births riskier across species

A new comparative review, published in The Anatomical Record, examines factors that may lead to birth complications among humans and other mammals. The study suggests that faetal sex may play an important role in risky births in humans and several other species.
It's often thought that human childbirth is unusually difficult among mammals. The idea is that an evolutionary "obstetrical dilemma" arose because of our bipedal pelvic anatomy and increasing brain size over time. Larger babies passing through a narrow birth canal can increase the chance of obstructed labour, affecting mortality for both the baby and mother. Yet difficult births, including cases in which a faetus is too large for the birth canal, occur across many placental mammals.

Some research has suggested that the obstetrical dilemma was solved by relatively earlier births, but other studies found no evidence that humans have shorter gestations than other apes, even after controlling for body size. Furthermore, researchers involved in the new study say there is a maximum fetus size compatible with safe delivery, and when it is exceeded, obstructed birth results. In other words, birth size and weight are known to be associated with difficult delivery.

The new study suggests, however, that because male babies also tend to be larger, male births tend to be riskier. The team says this pattern is not restricted to humans.

"Most taxa, including humans, displayed a bias toward larger male fetuses. Fetal sex has nonetheless not been incorporated in evolutionary perspectives of childbirth, perhaps because it is often assumed that the sex of each baby is determined at random, since most mothers are likely to produce both sons and daughters," the study authors write.

"Every mother has the potential to gestate both offspring through the reproductive career. Hence, it might be assumed that selection has acted on offspring size in general to resolve the obstetrical dilemma. As we show, however, the risks of birth complications are not equal for sons and daughters."

Researchers compiled sex-specific birth-weight data for 140 placental mammal species across 11 mammal orders and compared sex differences among newborns with adult body-size differences and developmental style. They then searched for reports of difficult birth by offspring sex.

This analysis led the authors to propose the "costly son" hypothesis, which states that larger male offspring may raise birth risks for both mothers and babies. They found that male newborns were more often larger than female newborns across many species. In humans, boys are, on average, heavier by around 3% to 4%, have bodies that are around 1% to 1.7% longer and have bigger heads at birth.

In particular, larger male newborns were common in species in which adult males are larger than adult females. Species with male-biased adult size differences were about six times more likely to have larger male newborns than species in which adult females are larger.

The team says evidence from humans, livestock and some other mammals suggests male fetuses are more prone to difficult births (referred to as dystocia), especially when newborns are relatively large compared with the mother. They note that data on birth complications by offspring sex are scarce outside humans and domesticated animals, leading to a focus on humans and domesticated animals rather than wild animals.

"Where sufficient evidence exists—principally in precocial domesticated species and some other ungulates—larger male fetuses are associated with an elevated risk of dystocia. In several primate species where dystocia is reported, male neonates have larger average anatomical dimensions than females," the researchers write.

Part 1

Comment by Dr. Krishna Kumari Challa on September 10, 2026 at 10:03am

The researchers mapped a specific four-step neural highway originating at olfactory sensory neurons in the nose and ending at glutamatergic neurons in the amygdala that translate physical air movement in the nose into emotional states.
They found that the speed of sensory signals from nasal airflow can directly push anxiety in opposite directions. Slow airflow at 2 Hz acted as a calming signal, reducing anxiety-like behavior in the mice, while fast airflow at 7 Hz had the opposite effect, increasing anxiety-like behavior. Airflow at 4 Hz, meanwhile, produced no significant change in anxiety.

Slow nasal stimulation activates PV⁺ interneurons in the perirhinal cortex, which in turn inhibit anxiety-promoting glutamatergic neurons in the basolateral amygdala. When the researchers silenced the connection between the olfactory bulb and the perirhinal cortex, this breathing-dependent control of anxiety disappeared completely.
Mice that received two hours of slow 2 Hz nasal airflow daily for two weeks showed restored normal high-gamma brain wave activity and reduced anxiety-like behaviors. These calming effects held strong for at least a week after the treatment stopped.

Together, these findings offer a more detailed view of how the nose and brain communicate, a pathway explaining how slow breathing calms anxiety. With anxiety disorders affecting more people worldwide than any other mental disorder, understanding this connection could open the door to effective, noninvasive ways of dealing with the issue.

Xinsong Guo et al, A nose-to-brain circuit underlies anxiety regulation by nasal afferent frequency in mice, Proceedings of the National Academy of Sciences (2026). DOI: 10.1073/pnas.2603853123

**

Part 2

Comment by Dr. Krishna Kumari Challa on September 10, 2026 at 10:01am

Newly mapped brain circuit offers clues to how slow nasal breathing eases anxiety

A slow breath in and out does the trick for many people when calming their nerves and dealing with anxiety, a disorder that affects millions of people worldwide. Pranayama, Taoism and meditation have long used slow nasal breathing to ease a negative mood. How this simple act works its magic, however, has been tickling the gray cells of scientists curious to unravel the biological pathways behind it. Now, scientists may have found a clue.

A recent study published in the Proceedings of the National Academy of Sciences discovered a nose-to-brain circuit that may help explain how the rhythm of nasal breathing can influence anxiety.

Researchers mapped a specific neural highway running directly from the nose into the brain's emotional network. This circuit begins with olfactory sensory neurons in the nasal cavity and continues to mitral cells in the olfactory bulb, the brain's smell-processing center. It then connects to a specific type of neuron, parvalbumin-positive interneurons (PV⁺), in a nearby brain region called the perirhinal cortex, which in turn links to the amygdala, the brain's fear and anxiety hub.

The frequency of nasal stimulation appeared to steer anxiety in different directions. Slow, low-frequency stimulation eased anxiety and boosted high-gamma brain waves in the perirhinal cortex, while faster stimulation had the opposite effect, increasing anxiety.
Breathing happens largely on autopilot, with the brainstem setting its rhythm. The breath, however, also sends information back to the brain. The same nasal neurons that detect odours can sense the movement of air, and the rhythm of that airflow can synchronize activity in brain regions involved in emotion. Humans have used slow breathing for ages to influence emotional states, even without conscious control.
Despite its widespread use, researchers didn't know whether simply changing the pace of this nasal sensory signal could directly shift anxiety, nor had they pinpointed the exact brain pathway connecting nasal airflow to emotional states. In this study, researchers identified that missing link, exposing the brain pathway that could explain why slow, deliberate breathing feels so calming.
Part 1

Comment by Dr. Krishna Kumari Challa on September 9, 2026 at 10:09am

We saw the results, we looked at ourselves, we said, 'this can't be correct'!

Arctic Rivers Are Breaking The Rules of Erosion

And scientists formed a new theory around Arctic erosion

Arctic landscapes are eroding much faster than previously thought, according to new SFU research. Fueled by climate change and extreme weather events, Arctic erosion is leading to the creation of new river systems as ice in frozen riverbeds melts. Earth scientists previously believed that the ice acted as a sort of glue, holding the landscape together and slowing down erosion. But surprising new findings suggest thawing ice in the ground can actually increase erosion rates up to 10 times compared to unfrozen rivers. SFU researchers explain how they carried out their research and what impact it could have.

https://www.nature.com/articles/s43247-026-03468-1

Comment by Dr. Krishna Kumari Challa on September 9, 2026 at 9:59am

A Mold Living in Your Gut May Help Protect Against Radiation Damage

Mold isn't typically something you want growing inside your body.

But in the case of Mucor racemosus, there may be compelling reasons to make an exception.

That's because this symbiotic fungus that lives inside the human gut appears capable of protecting us from radiation, according to a new study in PNAS.

It might sound a bit hard to believe, but this isn't the first time we've seen fungi doing weird things with radiation.

We know that there are different kinds of radiation-resistant fungi, including species that survive being blasted with up to 200 times the fatal human dose of X-rays.

There's also the funky world of radiotrophic fungi, which use radiation as an energy source – like the bizarre fungus living its best life in the radioactive remains of the Chernobyl Nuclear Power Plant.

M. racemosus has a different kind of parlor trick for radiation, but it's no less impressive.
In their research, a team of scientists found the fungus can confer protection from radiation to its host through a couple of different mechanisms, suggesting M. racemosus may be a beneficial presence in the gut.

In experiments with mice exposed to radiation, the researchers found that animals administered M. racemosus experienced less weight loss, inflammation, and oxidative stress than control mice that weren't given a fungal dose, suggesting M. racemosus provided the treated animals with a radioprotective effect.

This radioprotective effect was boosted when the researchers preadapted the fungus to the oxygen-poor conditions of the gut.

https://www.pnas.org/doi/10.1073/pnas.2608386123

Comment by Dr. Krishna Kumari Challa on September 9, 2026 at 9:43am

Xanthelasma and its association with developing major cardio-cerebrovascular events

A Warning Sign of Heart Attack And Stroke May Show Up on Your Face

Atherosclerosis, the accumulation of fatty plaques in the arteries that causes restricted blood flow, is responsible for most heart attacks and strokes – but it often builds up slowly and silently, without symptoms, before causing a major medical emergency.

That's why researchers are looking for warning signs of atherosclerosis that might help doctors spot it earlier.

A new study, published in Atherosclerosis, looks at a condition called xanthelasma, where yellow patches appear around the eyes.

Those patches puff up when immune cells called macrophages get stuffed with cholesterol and other fats. The condition is often (but not always) associated with higher cholesterol in the blood, too.

As fatty clumps also play a role in atherosclerosis, researchers thought there might be a link.
A few studies have supported the association between xanthelasma and an increased risk of cardiovascular events, while others debate that it may not be an independent risk factor once traditional risk factors are accounted for.
The study analyzed health data from 17,925 people diagnosed with xanthelasma and the same number of matched controls – people with presbyopia, a condition that leads to farsightedness, chosen because it would have involved an eye examination, ensuring the controls didn't have xanthelasma.
Across the first year of data, 1 percent of those with xanthelasma (178 patients) suffered a heart attack compared to 0.35 percent (or 63) of the controls.

For strokes, the respective figures were 0.95 percent and 0.3 percent, and for transient ischemic attack (TIA) or a 'mini-stroke', it was 0.6 percent and 0.19 percent.
Those are all low percentages, but the risk was several times larger for the xanthelasma group.

The gap between the two groups narrowed slightly over time, but at the 5- and 10-year time points, the risk was still substantially higher for those with xanthelasma.

Xanthelasma is associated with higher short- and long-term incidence of MACCEs up to 10 years, highlighting its value as a clinical marker for cardiocerebrovascular risk stratification and preventive management," write the researchers.

Incidence rates of these cardiac events were similar in the xanthelasma group whether or not they had abnormally high levels of fat in their blood – suggesting this isn't the only underlying factor at play.

While the pale, puffy patches that characterize xanthelasma are seen as harmless in themselves, the findings are more evidence that they could signify something else, and perhaps future cardiovascular problems.
This new study study suggests that xanthelasma can be considered as a risk factor for future MACCEs.
Xanthelasma patches are easy for doctors to spot, and for these people at least, may be a useful warning sign so that lifestyle changes or medications could be put in place early – before MACCEs are triggered.

https://www.atherosclerosis-journal.com/article/S0021-9150(26)00013-4/fulltext

Comment by Dr. Krishna Kumari Challa on September 9, 2026 at 9:36am

Bunsen burners make poor air-cleansers

Bunsen burners’ reputation for sterilizing workplaces flames out

Study shows that the venerable device does not waft bacteria away from workbenches, as is often assumed.

Bunsen burners, long used to cleanse airspaces and surfaces in labs of bacteria-laden particles, aren’t actually very effective at doing so, and might even make contamination worse. Researchers seeded the air above lab benches with the bacterium Gordonia rubripertincta and opened two Petri dishes — one near a lit Bunsen burner and one near an unlit one. They found that in several trials of differently sized burners, bacterial levels in dishes beside lit burners were as high as or higher than the other ones.

https://journals.asm.org/doi/10.1128/spectrum.01028-26

https://www.nature.com/articles/d41586-026-02758-0?utm_source=Live+...

Comment by Dr. Krishna Kumari Challa on September 9, 2026 at 9:21am

Almost half of farmers are being poisoned
There are more than 400 million cases of unintentional, acute pesticide poisoning every year, finds a new estimate — meaning that an estimated 46% of farmers worldwide are being poisoned. The analysis suggests there are 11,000 pesticide-related deaths annually, with nearly 60% of these in India. And that’s not taking into account long-term health impacts that are not immediately felt, such as a possible link with Parkinson’s disease.

https://www.frontiersin.org/journals/public-health/articles/10.3389...

Comment by Dr. Krishna Kumari Challa on September 9, 2026 at 9:16am

What students gain and lose as AI chatbots take over parts of university teaching
AI tools can provide timely, accessible feedback, tutoring, practice, and language support while enabling institutions to set boundaries on student AI use. Risks include inaccuracies, biased simplification, environmental costs, and limited governance. Replacing educators may also reduce reciprocal recognition, adaptive teaching, and students’ sense that their intellectual development is seriously judged.

Thomas Corbin et al, Hybrid reading practices: how GenAI summarisers can support rather than replace reading, Studies in Higher Education (2026). DOI: 10.1080/03075079.2026.2708138

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