The silvery fur of the hamadryas baboon is, under a spectrometer, nearly the exact color of moonlight, which may explain why ancient Egyptians made a monkey the face of their moon god, according to a new study in Time and Mind.

The work, from biological anthropologist Nathaniel Dominy of Dartmouth College and primatologist Catherine Hobaiter of the University of St Andrews, takes an old Egyptological question and points an instrument at it. Thoth, god of the moon, writing, and magic, had two sacred animals: the ibis and the baboon. The ibis makes sense. A curved beak echoing a crescent, white plumage the same color as the moon’s glow.

The baboon, however, has long “defied explanation,” as one Egyptologist put it; the key problem being that baboons didn’t live in Egypt.

Egypt’s pantheon features many local creatures, from the jackals that haunted its cemeteries to the cow that stood in for the mother goddess Hathor. But no wild baboon has ever been found in Holocene Egypt. The hundreds recovered from tombs and temples were all imports, carried in by ship from somewhere down the Red Sea coast. Of all the animal gods, the baboon is the only foreigner.

“Why would two such different animals be used to represent one deity? Most other Egyptian deities are represented by just one type of animal. Ancient Egyptians were familiar with at least three species of ibis, but they chose the white one for embodying Thoth. They were also familiar with two species of baboon, along with vervet monkeys and patas monkeys, but again they chose the silver-white species,” explained lead author Professor Catherine Hobaiter in a press statement.

According to the study, the Egyptians were picky. They knew two species of baboon and three of ibis, and each time they deified only one of each.

“Sacred ibises and hamadryas baboons are different in many ways, but one thing that unites them is their moon-like colour,” Hobaiter said.

To test whether color was the thread, the team recorded reflectance spectra from the hair of 12 baboon specimens at the American Museum of Natural History and lined them up against the measured spectrum of moonlight. The olive baboon came back green, peaking around 525 to 650 nanometers (which is precisely why it is called the olive baboon). The hamadryas came back silver-gray, roughly 65 percent brighter, with a curve the authors call “indistinguishable from moonlight.”

According to the study and historical records, the living emblem of Thoth is not just the hamadryas but the mature male, with his heavy silver shoulder mantle and white cheek ruffs. This head of hair is so reflective the authors clock it as brighter than a golden lion tamarin, a monkey practically famous for glowing. The Germans noticed too. Their name for the animal is Silberpavian, the silver baboon.

There is a stranger layer beneath the color. Egyptians kept baboons in their temples partly to watch them, because the animals seemed to answer to the moon. There are historical records which indicate that male baboons in Egypt, during a fifth-century solar eclipse, fell into a state of “grief” and, according to the ancient writer, entered a sort of trance of reverence. 

Modern ethologists watching zoo baboons during the 2017 total eclipse logged something uncomfortably close: activity falling away, the animals going quiet and huddling together. The Egyptians, in effect, may have kept a small colony of living eclipse detectors and read their unease as devotion.

History being what it is, and not an exact science, the authors are careful not to pretend that their findings are direct evidence as to why Ancient Egyptians made gods of baboons. A spectrometer can confirm that a baboon is the color of moonlight. It cannot confirm that the color is why anyone bowed to it. The argument rests on a 2024 etymology tracing Thoth’s name to a word meaning roughly “bright-thing.”

There is also an irony the study mostly steps around. The male’s silver mantle did not evolve to look like the moon; it evolved as a sexual signal, a way for dominant males to advertise themselves to other baboons. The Egyptians took a mating ornament and read it as a message from the sky.

That may be the most human thing in the whole account. The Egyptians were meticulous observers who noticed that one animal, in one sex, at one particular brightness, resembled the thing they worshiped, and decided the resemblance meant something.

One of those baboons even has a name. Harnufi was brought to Egypt in the sixth year of Ptolemy V and entombed 31 years later, on September 6, 168 BC. Someone counted out his life in years, mummified him, and laid him down as a small gray piece of the moon.

The 13-sided tile that solved a half-century-old math problem, discovered by an amateur mathematician at his kitchen table in 2022, turns out to bend light into a twisting pinwheel unlike anything produced by an ordinary crystal, according to a new study in Nature Communications.

The work, from physicists at the University of Tokyo and NTT’s Nanophotonics Center in Japan, marks the first time anyone has taken the celebrated “einstein” tile—a term derived from the German ein Stein, meaning “one stone,” and unrelated to the famous physicist—out of pure mathematics and asked what it does to light.

The answer is a form of optical handedness that even quasicrystals, the closest known relatives of this structure, do not possess.

Unlike circles or squares, which are identical when mirrored, our hands are not. They may be reflections of each other, but you can’t place one perfectly on top of the other, no matter how you rotate it. Likewise, a handed structure “notices” the difference between left- and right-circularly polarized light, while a mirror-symmetric structure—such as a circle—cannot. The flat tile pattern has no mirror image identical to itself, much like your hands, and that asymmetry becomes imprinted onto the light it diffracts.

“We found that the diffraction patterns themselves become chiral because the structure lacks mirror symmetry,” Masaya Notomi, the study’s senior author, explained in a press statement. “This kind of optical response is fundamentally different from that observed in conventional quasicrystalline materials.”

To see why that matters, it helps to go back to the shape.

The Einstein Problem

Mathematicians had pursued a particular puzzle for roughly 50 years, known as the “Einstein problem.” The question was whether a single shape could completely tile a flat plane, but only in a pattern that never repeats. Roger Penrose reduced the problem to two tiles in the 1970s. Finding a single tile remained out of reach.

Then, in November 2022, David Smith, an amateur mathematician and retired print technician from Bridlington, England, found one while tinkering with shape-tiling software. He cut copies out of cardstock, laid them across his table, and watched the pattern refuse to settle. He nicknamed it “the hat” because it looks vaguely like a fedora. Smith and three collaborators posted the proof in March 2023, and it made news around the world.

That same year, a 2023 theory paper by physicist Joshua Socolar had already predicted chiral diffraction from hat tilings, but there was one wrinkle. The hat needs its own mirror image sprinkled among the tiles to work, a hint of handedness baked into the geometry. That handedness is exactly what the new study chases into the behavior of light, so to do it, the team led by Yuto Moritake did something a mathematician would never bother with: they built the thing.

They marked the center of each hat tile with a point, producing a pattern with perfect threefold rotational symmetry (it looks identical when you turn it a third of the way around) but no mirror symmetry, meaning its reflection is a genuinely different object. Then they etched that pattern into a 350-nanometer-thick film of silicon nitride, drilling 372,100 tiny holes across a patch half a millimeter on a side.

Shine a laser through a regular grid of holes, and you get a neat, symmetric spray of dots on the far wall—a diffraction pattern, the same effect that throws rainbows off a CD. The team fired a green laser at their aperiodic version and photographed what came out.

It was a pinwheel.

A Quasicrystal Structure

The diffraction pattern was sharp and filled with bright, well-defined spots—the signature of long-range order—and evidence that the structure behaves like a true quasicrystal despite never repeating. But unlike conventional diffraction patterns, the entire arrangement twisted in one direction, with no mirror symmetry anywhere in the image. When the researchers repeated the experiment using the mirror-image version of the tile, the pinwheel twisted in the opposite direction.

So the team did what all scientists do in these situations. They just started blasting different kinds of light at it.

“Because the structure is chiral, a circular-polarization dependence should not be forbidden. But on the first trial, I couldn’t find any difference. I thought it might be very weak, so I changed the camera to a more sensitive one — and then I finally found it,” Moritake told The Debrief. “I somehow expected it, but I was still surprised when I found it.”

The strange result came with that circularly polarized light test. It’s a light whose electric field corkscrews as it travels, clockwise or counterclockwise. The pattern responded differently depending on which way the light was spinning. Feed it left-handed light and certain spots brightened; feed it right-handed light and different ones did. That behavior, the authors note, has never been seen in a conventional quasicrystal.

Underneath all of it sits a piece of elegant bookkeeping. The angle of the pinwheel’s twist, about 15.5 degrees, isn’t arbitrary. Moritake’s team showed that it falls straight out of the Fibonacci sequence and the golden ratio, the same numbers that govern the tile’s geometry. The shape’s real-world twist is written directly into how it scatters light.

The findings are a scientific first, but the paper is quick to point out that this is fundamental physics and not a product. There is no device here, and the authors are careful to call their structure a possible “platform” rather than a working component. The chirality at play is a strictly two-dimensional kind (the absence of a mirror line within the flat pattern), not the three-dimensional handedness of a molecule or, you know, your hands.

“At least, this effect is forbidden in an inversion-symmetric structure, so it reflects the chiral nature of the monotile,” Moritake said. “Of course, this effect could appear in other structures too. But I don’t know of another lattice that is both chiral and quasiperiodic like this one.”

Still, the result does something basic research quietly does all the time: it takes an object discovered for no reason beyond that it was beautiful and finds that nature had a use for it. Breaking a structure’s mirror symmetry is how physicists coax materials into nonlinear optical tricks and polarization-sensitive behavior, and aperiodic tiles offer a new and largely unexplored way in.

“Mathematical discoveries have always led to important developments in physics,” Moritake said. “The monotile is generated from a honeycomb frame, and in nanophotonics, the honeycomb lattice is used constantly because it produces interesting phenomena — graphene is the representative example. So I thought the monotile lattice might be interesting in real physics too.”

For a shape that started as a puzzle on a hobbyist’s kitchen table, that’s a long way to travel.

The first proper brain scan involving the effects of mescaline found the drug ignoring the regions where psychedelic research has spent a decade studying, settling instead on the one structure no one really expected.

Sometime around 3,700 BC, someone in what is now southwest Texas cut two tops off a peyote cactus and dried them. They spent most of the twentieth century in a drawer at the Witte Museum in San Antonio, and when chemists finally analyzed them in the early 2000s, the mescaline was still detectable — roughly 2% alkaloids by weight, 5,700 years on.

Those dried-out cactus tops, where the drug compound is concentrated, remain the oldest plant drug ever to give up a major bioactive compound to chemical analysis. And with thousands of years of use, mescaline remains a bit of a scientific mystery.

Mescaline became a Schedule 1 substance under the Controlled Substances Act in 1970, and the classification effectively ended research on it. LSD and psilocybin eventually clawed their way back into laboratories for scientific research, but mescaline, the older compound by several thousand years, doesn’t have the same level of lab testing.

Now, a new study in Neuroscience Bulletin has become the first to properly look, and the answer is not what most expected.

Researchers at Northeastern University’s Center for Translational Neuroimaging scanned 24 rats, evenly split by sex. After a single dose of mescaline, while the animals were awake (anesthesia flattens the very signals a drug study is trying to read), the drug largely ignored the forebrain. It went almost entirely for the cerebellum, which is a strange location for a psychedelic. 

The cerebellum is the lump at the back and bottom of the brain where balance and motor coordination live. It also holds more than half of all the neurons in the brain, and everything it computes leaves through just three narrow output channels.

An interpretation, proposed by neuroscientist Anna Devor in 2002, is that the cerebellum is the “Great Gate.” As the brain receives sensory information, it acts as a filter that suppresses the sensory information that the brain already predicted and passes along only what it did not expect. A working brain spends most of its time discarding what it saw coming.

Under mescaline, the gate appeared to come off its hinges.

Activity inside the cerebellum dropped sharply, while its connections outward multiplied to the hippocampus, the thalamus, the sensory cortex, and the midbrain. Quieter on the inside, wired to far more on the outside. The researchers read this as a filter that has stopped filtering and started broadcasting, pushing raw sensory information into regions that normally receive it neatly packaged.

“Wouldn’t it be devastating if you didn’t ‘gate’ all of that sensory information out?” senior author Craig Ferris explained in a university press statement.

The clearest evidence for that reading came from a smell test. Rats were given almond odor, a reliably rewarding stimulus, and in the control group, it lit up 48 of the 169 brain regions the team tracked. Under mescaline, the response was essentially abolished, flattened close to nothing across the board.

Broken down by modality, smell, touch, and hearing were all measurably blunted, while the visual system showed no significant change at all — a peculiar result for a compound whose entire cultural reputation rests on what it does to sight. 

The authors put the discrepancy down to species differences, reasonably enough given that rats navigate by nose and whisker, but it remains one of the odder findings in the paper. What makes this significant is the comparison. 

Mescaline, LSD, and psilocybin all act on the same target, the 5-HT2A serotonin receptor, and all three produce broadly similar experiences in people, which has encouraged researchers to treat findings from one as transferable to the others. However, brains don’t seem to cooperate.

Earlier work from this same lab found LSD acting on the prefrontal cortex, thalamus, and hippocampus, and psilocybin engaging cortico-striato-thalamic circuits. Mescaline’s acute signature sat in neither place.

“The power of mescaline to me is that it is doing something different than other psychedelics,” said lead author Noah Cavallaro. “Essentially, the cerebellum is being shut down internally, but it’s talking more to other parts of the brain.”

The distinctiveness is narrower than it first appears, though. The lab’s own psilocybin work also produced pronounced cerebellar hyperconnectivity, so the sprawling network changes are not unique to mescaline; what looks specific to it is the acute suppression, the cerebellum falling quiet while the rest of the brain carried on largely unaffected.

“If two compounds produce similar hallucinogenic symptoms through different neural pathways, comparing them could help us pinpoint what’s actually causing those specific experiences,” Cavallaro said.

That being said, there are some cautions offered in the paper. First, these were rats, and rat and human brains differ most in the cerebellar-cortical wiring. Second, only one dose was tested. Third, the team did not monitor heart rate or breathing during scanning, so ordinary cardiovascular effects cannot be cleanly separated from neural ones.

Lastly, the researchers also flagged recent work showing that the scanner signal itself can run opposite to a brain region’s actual oxygen use, which complicates reading any of these images as direct neural activity. The one previous attempt to image mescaline in humans, a small study decades ago, found a different pattern entirely.

With all that being said, the paper presents a key social issue. Mescaline’s status as a drug has left it largely untested, and only now are we learning about what it can do to the brain, outside of the anecdotes of its users.

After fifty years of regulatory silence, scientists are just starting to answer a question people have arguably been asking since the Neolithic.