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Comment by Dr. Krishna Kumari Challa yesterday

Invisible fertility crisis: Chemicals and climate change threaten reproduction across species

The rise in infertility is not limited to humans, as environmental stressors are quietly undermining the reproductive potential of different forms of life. A recent review published in npj Emerging Contaminants investigated how today's environmental challenges are shaping the reproductive capacity of both humans and animals.

From the analysis emerged two major forces—synthetic chemicals and warming climate—that are not acting in isolation but as a unit, placing growing pressure on fertility and fecundity (biological capacity of an organism to reproduce) across a wide spectrum of species.

The effects range from skewed sex ratios and poorer egg and sperm quality to developmental abnormalities and falling population numbers. The impact is not limited to a single generation; it carries its mark into future generations and tends to worsen when chemical exposure and climatic changes hit together.

Susanne M. Brander et al, Impacts of environmental stressors on fertility and fecundity across taxa, with implications for planetary health, npj Emerging Contaminants (2026). DOI: 10.1038/s44454-026-00032-6

Comment by Dr. Krishna Kumari Challa yesterday

The researchers estimate that any cognitive differences would be very small at only 0.14 standard deviations. This is based on the weak links between brain anatomy and cognitive performance seen in modern humans. That suggests that the mental abilities of the two groups living in Eurasia were similar on average.

Therefore, according to the team, the range of intelligence in Neanderthals and in humans would have overlapped heavily. So some Neanderthals could have been more capable than some early humans.

"If cognitive differences between modern human populations are not considered significant, Neanderthal differences from their contemporaries should not be either," said the researchers.

In other words, we shouldn't treat Neanderthal differences as especially meaningful if similar differences among humans aren't.

P. Thomas Schoenemann et al, Neanderthal brain and cognition reconsidered, Proceedings of the National Academy of Sciences (2026). DOI: 10.1073/pnas.2426638123

Part 2

Comment by Dr. Krishna Kumari Challa yesterday

Neanderthal brains were not very different from human brains!

We appear to have more in common with our Neanderthal cousins than outward appearances would suggest. New research published in the journal Proceedings of the National Academy of Sciences suggests that the differences between Neanderthal brains and the brains of early modern humans (Homo sapiens) were no greater than the differences we see between various groups of people living today. The findings could challenge the long-held theory about why Neanderthals disappeared around 40,000 years ago.

The popular narrative suggests that Neanderthals were not as smart as the early humans who colonized their territory in Eurasia and ultimately replaced them.

The stock image of Neanderthals as brutish, cognitively inferior cavemen largely stems from differences in the shape of their skulls. Because theirs were more elongated and less round than ours, scientists assumed their brain organization was less advanced. Consequently, it was thought they lacked the memory and language skills that would have been necessary to compete with us. But this may not be correct.
A team of scientists took brain scans (MRIs) from two large modern groups of people: one made up of ethnic Han Chinese individuals and the other composed of Americans with European ancestry. They measured the volumes of 13 different brain regions in these groups and compared them with previously reported differences between Neanderthals and early modern humans who lived alongside them. These measurements were taken from endocasts, 3D models of the inside of Neanderthal skulls used to estimate brain shape and size.

They found that in 9 of the 13 brain regions, the volume differences between the modern Chinese and modern US samples were larger than those between Neanderthals and early humans. "The differences between modern human and Neanderthal brains, as estimated from endocranial reconstructions, do not meaningfully exceed those among different modern human populations," explained the study authors in their paper.

Part 1

Comment by Dr. Krishna Kumari Challa yesterday

Microplastics turn up in nearly every human brain sample, including healthy tissue

Tiny micro- and nanoplastic fragments seem to be turning up everywhere, including one of the most well-protected parts of the human body—the brain. In a recent study conducted by researchers, they found microplastics and nanoplastics (MNPs) in nearly all the brain samples they tested, both healthy and diseased human brains.

As per the findings published in Nature Health, the microplastic levels were the highest recorded in the study, reaching 129 micrograms per gram in tumor-affected brain tissue. The healthy brain and spinal cord tissue had considerably lower levels, with a median of 50.3 micrograms per gram. 

Studies have found that microplastics can enter the human body through breathing, eating, and skin contact. The brain is protected by an exceptionally selective filter called the blood-brain barrier, designed to keep harmful substances out of our most vital organ. Yet previous studies have found that microplastics can somehow bypass this defense and enter the brain. This is particularly concerning because very little is known about what these foreign particles do once inside, where they go and settle, or what concentrations they can reach.

The study authors realized that MNPs were present in almost all samples: 99.4% of diseased tissue samples and 100% of healthy tissue samples. Nanoplastics, which are smaller in size, were more abundant than microplastics. The team was even able to identify the type of plastic the tiny bits came from: PET, often used to make beverage bottles; polyethylene, commonly used in plastic bags; polyamide that makes up textiles like nylon and PVC found in plumbing and industrial equipment.

In diseased brains, levels were not uniform across the tissue, with higher concentrations near tumors, possibly due to weakened natural protection. They detected these particles in operating room environments, raising the possibility of exposure during medical procedures.
Their analysis also found that the larger the surface area of microplastics, the faster the tumor cell growth. While this doesn't mean microplastics cause cancer, it does raise questions about the role MNPS may play in how quickly the disease progresses, an area the researchers noted requires further exploration.

Tackling MNP pollution calls for joint action from policymakers, manufacturers, and consumers. Findings from this study, along with future research, can strengthen public awareness and drive demand for change, helping to push policies grounded in evidence.

Runting Li et al, Microplastics and nanoplastics in brain tumours and the healthy human brain, Nature Health (2026). DOI: 10.1038/s44360-026-00091-4

Comment by Dr. Krishna Kumari Challa yesterday

Excessive cholesterol in astrocytes linked to cognitive decline in Alzheimer's mice

Alzheimer's disease (AD) is a neurodegenerative disorder that leads to progressive memory loss and a decline in mental functions. Several past studies have linked this disease to the accumulation of the protein amyloid-β into sticky plaques that disrupt the function of neurons.

More recently, neuroscientists have uncovered the existence of the glymphatic system, a brain-wide system that facilitates the clearance of metabolic waste, including amyloid-β in excess, from brain tissue via the flow of cerebrospinal fluid.

Astrocytes, the most abundant type of glial cells in the CNS, play a central role in this waste clearance process. These cells are known to regulate cerebrospinal fluid movement via a protein called AQP4 (aquaporin-4), supporting the clearance of waste from brain tissue.

Researchers  set out to better understand how anomalous calcium activity in astrocytes impacts the glymphatic system. Their findings, published in Nature Neuroscience, suggest that elevated calcium activity in astrocytes mediates an increase in cholesterol levels, which in turn impairs the function of the glymphatic system in a genetically engineered model of AD.

Overall, the team's observations suggest that an accumulation of amyloid-β increases calcium activity in astrocytes, which in turn disrupts the brain's waste clearance system. It also offers hints about how these processes might contribute to the cognitive decline and memory loss observed in patients with AD.

If they are validated in humans, the results of this study could have key implications for the early treatment of AD. Specifically, they could help to identify or design pharmaceutical drugs that might prevent or reverse cognitive decline in the early stages of the disease or slow down its progression.

Zhan Zhang et al, Amyloid-β-driven glymphatic dysfunction in Alzheimer's disease model mice is driven by Ca²⁺-mediated increases in astrocytic cholesterol, Nature Neuroscience (2026). DOI: 10.1038/s41593-026-02261-9.

Comment by Dr. Krishna Kumari Challa on Tuesday

How two men smashed through a marathon barrier long thought unbreakable
Sabastian Sawe and Yomif Kejelcha completed the marathon in under two hours, breaking the previous world record by significant margins. Key factors included exceptionally high training volumes, optimized carbohydrate intake, advanced lightweight "supershoes" improving running economy, and favorable weather. These performances resulted from the convergence of physiological, biomechanical, nutritional, and technological advancements.

original article.

Comment by Dr. Krishna Kumari Challa on Tuesday

Why do we unconsciously imitate one another 

Comment by Dr. Krishna Kumari Challa on Tuesday

Six ways your smartwatch is lying to you, according to science
Smartwatches and fitness trackers often provide inaccurate estimates for calories burned, step counts, heart rate, sleep stages, recovery scores, and VO₂max due to reliance on indirect measurements and sensor limitations. These inaccuracies can mislead users about their health and fitness status, especially when used to guide diet, training intensity, or recovery. While useful for tracking general trends, individual metrics should be interpreted cautiously.

original article.

Comment by Dr. Krishna Kumari Challa on Tuesday

Half of AI health answers are wrong even though they sound convincing—new study
AI chatbots provided problematic or highly problematic health information in up to 58% of responses, with none reliably generating accurate reference lists. Performance was better for well-researched topics like cancer and vaccines, but accuracy dropped for open-ended questions and areas with less robust evidence. Users often misinterpret or misuse chatbot answers, and chatbots can fabricate references or repeat misinformation. These findings indicate current AI chatbots should not be relied upon as stand-alone medical authorities.

original article.

Comment by Dr. Krishna Kumari Challa on Tuesday

With the same black plumage, how do crows tell one another apart? Earlier research has shown that their calls are individually specific, functioning in the same way as human voices. Female crows tend to have higher voices than males, partly due to body size.

Crows also vary in body size and shape and have similarly diverse bills; the tips grow continuously, but the bill shape is stable nearer the base.
Crows may also be able to recognize individuals by how they move—in their case, fly.

Jessica L. Yorzinski et al, Inter- and intra-individual variation in the feather coloration of American crows, Journal of Avian Biology (2026). DOI: 10.1002/jav.03604

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