Телеграм канал «Eli5a»

Men's brains shrink faster with age. It still doesn't explain Alzheimer's.

Across 12,638 MRI scans from 4,726 cognitively healthy adults, men's brains lost volume in more regions as they aged than women's did. Alzheimer's is diagnosed more often in women, and per the abstract, these aging differences are unlikely to explain why.

Ravndal et al., PNAS, 2025.
https://doi.org/10.1073/pnas.2510486122

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Image: Striatum structural MRI by Lindsay W. Hall and Geoff B. Hall, CC0 (https://creativecommons.org/publicdomain/zero/1.0/), via Wikimedia Commons (shown in grayscale, cropped to 4:5 from the original): https://commons.wikimedia.org/wiki/File:Striatum_Structural_MRI.png

A tooth just moved the platypus timeline 12 million years.

Two Early Pleistocene teeth from southwestern New South Wales are the youngest known fossils of the toothed platypus Obdurodon. Every earlier find dated to the Oligocene or Miocene, so the new record extends the toothed-platypus lineage by roughly 12 million years, per the accepted manuscript. Today's platypus has no teeth as an adult.

Nink, Worthy & Prideaux, Australian Zoologist, 2026 (accepted manuscript, published online ahead of issue assignment).
https://doi.org/10.1071/AZ26018

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Photo: Duck-billed platypus (Ornithorhynchus anatinus), Scottsdale, by Charles J. Sharp, CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), via Wikimedia Commons (shown in grayscale, cropped to 4:5 from the original): https://commons.wikimedia.org/wiki/File:Duck-billed_platypus_(Ornithorhynchus_anatinus)_Scottsdale.jpg

The people mosquitoes chose carried less of one skin bacteria genus.

In a study of 37 volunteers, people were split into high-attraction (22) and low-attraction (15) groups by an olfactometer test with Aedes aegypti. At genus level, Bacillus made up 62.72% of sequenced skin bacteria in the low-attraction group versus 0.57% in the high-attraction group.

Two caveats matter. First, the authors themselves flag that pre-sequencing amplification overrepresented Bacillus, so those percentages are inflated in absolute terms; they argue the between-group gap still holds because the bias hit all samples equally. Second, the paper's microbiome analyses list group sizes of 21 and 16 rather than the 22 and 15 used for the behavior split - an internal inconsistency we flag as a material limitation rather than resolve.

The causal part is animal work: applying two Bacillus species (B. licheniformis and B. paralicheniformis) to cynomolgus monkey skin significantly reduced mosquito attraction, and the bacteria shifted skin odor compounds (p-cresol, decanoic acid) linked to repellency. In humans this is an association only. No human repellent effect was tested, the effect was not validated in Anopheles or Culex mosquitoes, and it is not a product.

Gu et al., Nature Communications, 2026. https://doi.org/10.1038/s41467-026-78356-5

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Photo: Aedes aegypti, James Gathany / CDC, public domain, via Wikimedia Commons

o caveats matter. First, the authors themselves flag that pre-sequencing amplification overrepresented Bacillus, so those percentages are inflated in absolute terms; they argue the between-group gap still holds because the bias hit all samples equally. Second, the paper's microbiome analyses list group sizes of 21 and 16 rather than the 22 and 15 used for the behavior split - an internal inconsistency we flag as a material limitation rather than resolve.

o caveats matter. First, the authors themselves flag that pre-sequencing amplification overrepresented Bacillus, so those percentages are inflated in absolute terms; they argue the between-group gap still holds because the bias hit all samples equally. Second, the paper's microbiome analyses list group sizes of 21 and 16 rather than the 22 and 15 used for the behavior split - an internal inconsistency we flag as a material limitation rather than resolve.

, people were split into high-attraction (22) and low-attraction (15) groups by an olfactometer test with Aedes aegypti. At genus level, Bacillus made up 62.72% of sequenced skin bacteria in the low-attraction group versus 0.57% in the high-attraction group.

, people were split into high-attraction (22) and low-attraction (15) groups by an olfactometer test with Aedes aegypti. At genus level, Bacillus made up 62.72% of sequenced skin bacteria in the low-attraction group versus 0.57% in the high-attraction group.