science

cross-posted from: https://lemmy.world/post/42158359

Background and Evolutionary Context

Human iris pigmentation varies widely across populations and is largely established during prenatal and early postnatal development. Genetic variation, particularly in regulatory regions near OCA2 and HERC2., explains much of this diversity. However, these genes primarily influence how pigment organelles develop and are organized , not whether pigment exists at all.

Light-colored eyes, especially blue eyes, result mainly from **structural light scattering within the iris stroma, not from an absence of melanin. This makes iris color unusually sensitive to developmental microconditions that affect cellular organization.

Water is the dominant component of embryonic tissues, including the developing eye. Importantly, the isotopic composition of water varies naturally with climate and geography. High-latitude and glacial environments are consistently depleted in deuterium relative to temperate and tropical regions. These isotopic differences are stable over generational timescales and therefore represent a plausible environmental variable during human evolution.

Experimental studies in non-pigment cell systems show that altered deuterium-to-hydrogen (D/H) ratios can influence cellular metabolism, differentiation, and proton-coupled transport. However, the potential role of water isotopes in human developmental traits has not been systematically examined , particularly for traits dependent on cellular architecture rather than bulk chemistry.

Central Hypothesis

Variation in environmental deuterium levels during early development biases melanosome maturation and spatial organization in neural crest–derived iris melanocytes, producing heritable differences in iris light-scattering properties that act within genetically defined pigmentation limits. 

This hypothesis does not propose a new inheritance mechanism. Instead, it frames water isotopes as a , developmental modifier, that could contribute to population-level phenotypic patterns under stable environmental conditions.

Rationale

This hypothesis is supported by five established findings:

1. Natural water sources show large, predictable geographic variation in deuterium content.
2. D/H ratios influence cellular redox balance and proton-dependent processes.
3. Iris melanocytes differ in regulation from skin melanocytes and show early developmental fixation.
4. Melanosome pH, size, and maturation state strongly influence pigmentation outcomes.
5. Structural light scattering, rather than pigment concentration alone, determines light eye coloration.

Together, these observations suggest that even modest isotopic effects during development could produce visible phenotypic differences subject to evolutionary filtering.

Specific Aim 1

Determine whether developmental D/H ratios alter melanosome maturation and architecture in iris melanocytes.**

Approach

Neural crest–derived melanoblasts will be differentiated under controlled isotopic conditions representing low, typical, and elevated environmental deuterium levels. Outcomes will include:

• Melanosome size and shape distributions

• Relative proportions of immature and mature melanosomes

• Intramelanosomal pH

• Eumelanin-to-pheomelanin ratios

  Expected Outcome

We expect D/H variation to bias melanosome architecture without necessarily changing total pigment production.

Specific Aim 2

Assess whether isotopically induced architectural changes modify optical properties relevant to iris color.

Approach

Using three-dimensional iris stromal models:

• Quantify melanosome spacing and cellular organization

• Measure wavelength-dependent light scattering

• Relate structural parameters to optical behavior

  Expected Outcome

Architectural shifts are expected to produce scattering profiles consistent with lighter or darker iris phenotypes.

Specific Aim 3

Evaluate interaction between isotopic effects and known pigmentation genetics in an evolutionary framework.**

Approach

Key experiments will be repeated using cells stratified by OCA2/HERC2 regulatory variants. This will test whether isotopic effects:

Are consistent across genotypes Bias outcomes within genotype-specific pigmentation ranges

Expected Outcome

Results should support a gene–environment interaction model compatible with known evolutionary patterns of eye color variation.

Evolutionary Significance

If confirmed, this work would identify. stable environmental isotope gradients. as a previously unrecognized contributor to human phenotypic diversity. Such gradients could act as developmental filters, subtly shaping traits like iris pigmentation that are sensitive to microstructural organization.

This mechanism would not replace genetic explanations but could help explain why certain pigmentation phenotypes emerge and persist in specific ecological contexts during human evolution.

Summary

This project tests a narrowly defined, physically grounded hypothesis: that water isotope composition influences the developmental architecture of iris pigmentation. By integrating cell biology, optics, and evolutionary context, it offers a conservative but novel framework for understanding variation in a classic human trait.

Osuna-Mascaró hopes the work will inspire scientists to pay more attention to farm animals as well. Though he’s largely studied chimpanzees and cockatoos until now, he wants to continue to work with cows. He’s even put a cow screensaver on his phone. “I think most animals are living a rich life and have something really interesting to tell us,” he says. “We just have to ask the right questions.”

The continuing row highlights long-standing tensions over clinical research trials in Africa that are proposed and run by researchers in other countries. African scientists say that the Guinea-Bissau study shows how political pressure, funding interests and fragmented oversight can push local health priorities aside.

...“The calculation results show enhancements of fusion yields by orders of magnitude with currently available intense low-frequency laser fields,” highlighted the study.

For a collision energy of 1 keV—a level where fusion is normally almost impossible—the application of a 1.55 eV low-frequency laser can transform the reaction rate.

At 10^20 W/cm² intensity, the fusion probability increases by three orders of magnitude, while increasing the intensity to 5×10^21 W/cm² boosts the efficiency by a staggering nine orders of magnitude.

This dramatic increase effectively makes fusion at 1 keV (relatively low temperature) as probable as fusion at 10 keV without laser assistance...

We’re not sure if it’s exciting or not that scientists just discovered new ‘lifeforms’ inside of our bodies. Tiny bits of RNA, smaller than a virus, colonize bacteria inside our mouths and guts and have the power to transfer information that can be read by a cell.

Dubbed ‘wildly weird’ by the team of Stanford scientists writing about the find in Nature, the discovery now has a name: obelisks. And we ... don’t really know their end goal.

“It’s insane,” said Mark Peifer, a cell and developmental biologist at the University of North Carolina at Chapel Hill, according to Science. “The more we look, the more crazy things we see.”

Named obelisks because of their rod-shaped structures, they are even smaller than viruses, but they can still transmit instructions to cells. What they’re saying, however, we just don’t know.

It looks more like a worn sock than a fearsome predator. It moves slower than an escalator. By most accounts, it is a clumsy and near-sightless relic drifting in the twilight waters of the Arctic, lazily searching for food scraps.

But the Greenland shark, an animal one researcher (lovingly) said, “looks like it’s already dead”, is also one of the least understood, biologically enigmatic species on the planet.

But this month, scientists made a groundbreaking discovery: the sharks are not, in fact, blind. The newly published findings upend commonly held beliefs and expose the challenges of studying a shark that has long resisted the reaches of science. But the disruptive nature of the research also underscores the challenges scientists face in predicting how a rapidly changing climate might harm or help the elusive fish.

cross-posted from: https://mander.xyz/post/45811590

cross-posted from: https://mander.xyz/post/45810913

Cows are not usually credited with thinking on the hoof. They eat, they chew, they stand in fields performing an activity that may look like contemplation but is generally written off as digestion.

They are not typically thought to plan, let alone solve problems. A new study suggests we may have underestimated them.

The research describes what experts claim is the first documented case of flexible, multi-purpose tool use in cattle, observed in a cow named Veronika.

...

Veronika is a Swiss brown cow kept not for milk or meat but as a pet by Witgar Wiegele, an organic farmer and baker in Austria. More than a decade ago he noticed her using a long-handled brush, holding it in her mouth to scratch awkward parts of her body.

When video footage of this behaviour reached Alice Auersperg, a cognitive biologist at the University of Veterinary Medicine, Vienna, it struck her as unusual, largely because Veronika used the brush in different ways to scratch different parts of her body.

“It was immediately clear that this was not accidental,” Auersperg said. “This was a meaningful example of tool use in a species that is rarely considered from a cognitive perspective.”

Auersperg and her colleague Antonio Osuna-Mascaró conducted a series of trials. They placed a long-handled brush on the ground and recorded how Veronika used it.

...

When scratching broad, thick-skinned regions such as her back or rump, Veronika tended to use the bristled end, applying it with sweeping, forceful movements. When targeting softer, more sensitive areas of her lower body, she switched to using the handle to scratch herself, moving more slowly.

Because Veronika directs tools at her own body, researchers describe this as egocentric tool use, which is usually regarded as less complex than tool use aimed at external objects. Even so, flexible, multi-purpose use of a single tool is rare. Outside humans, it has previously been demonstrated convincingly only in chimpanzees, the researchers say in their paper.

They wrote in a study published in the journal Current Biology that the findings “invite a reassessment of livestock cognition”.

...

The researchers suspect that Veronika’s life circumstances have played a role in the emergence of this behaviour. Most cows do not reach her age and they are rarely given the opportunity to interact with a variety of potentially useful objects.

Her long lifespan, daily contact with humans, and access to a rich physical landscape probably created favorable conditions, they said. If that is true, there may be nothing very exceptional about Veronika, other than the opportunities she has been given to exercise her brain.

...

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