Professor John Manning, a member of Swansea University’s Applied Sports, Technology, Exercise and Medicine (A-STEM) research team, specializes in the study of digit ratio.

Digit ratio compares the length of the index finger, known as 2D, with the length of the ring finger, known as 4D. This measurement is called the 2D:4D ratio. Researchers use it as an indirect indicator of the balance of estrogen and testosterone a fetus may have been exposed to during the first trimester of pregnancy.

People thought to have had relatively higher exposure to estrogen than testosterone generally have a longer index finger (2D) compared with their ring finger (4D). This results in a higher 2D:4D ratio.

For the latest study, Manning worked with researchers from Istanbul University’s Department of Anthropology. Their findings were published in the journal Early Human Development.

Comparing Newborn Fingers and Head Size

The team examined 225 newborns, including 100 boys and 125 girls. They measured each baby’s 2D:4D ratio and compared it with head circumference.

Head circumference is commonly used as a general indicator of brain size in newborns. It has also been associated with later measurements of cognitive development and IQ, although many genetic, environmental, and developmental factors influence intelligence.

The researchers found that boys with a higher 2D:4D ratio (indicating high prenatal estrogen) also tended to have a larger head circumference. The same relationship was not observed in girls.

A Possible Clue to Human Brain Evolution

The results may support a theory known as the estrogenized ape hypothesis. This idea proposes that the evolution of larger human brains occurred alongside changes that made the human skeleton less robust and more physically feminine compared with those of earlier ancestors.

Professor Manning said: “This finding is relevant to human evolution because increases in brain size are found alongside feminization of the skeleton, what is known as the estrogenized ape hypothesis. High values of 2D:4D in males have been found to be related to elevated rates of heart problems, poor sperm counts and predisposition to schizophrenia.

“However, increases in brain size may offset these problems. Thus, the evolutionary drive for larger brains in humans may inevitably be linked to reductions in male viability including cardiovascular problems, infertility and rates of schizophrenia.”

The researchers suggest that larger brains may have provided major evolutionary advantages, even if the hormonal conditions associated with that development also carried biological costs for males.

Evolution May Have Involved Trade-Offs

According to the team, the findings add to evidence that prenatal estrogen may have played a positive role in the evolution of the human brain.

The study does not show that finger length directly determines brain size. Instead, the researchers view digit ratio as a possible marker of hormonal exposure during early fetal development. The results identify an association that may offer clues about how prenatal hormones influenced human evolution.

Manning’s earlier research has explored whether digit ratio can provide information about alcohol consumption, outcomes after contracting COVID-19, and oxygen consumption in footballers.

The strongest effect appeared when researchers combined isosteviol, a sweetener used by the food and beverage industry, with the antidepressant duloxetine. Together, the two compounds sharply reduced the growth of two important bacterial species associated with digestive health, blood sugar regulation, and immune function.

The scientists caution that the experiments were conducted in a laboratory rather than in people. More research will therefore be needed to determine whether the bacterial changes lead to meaningful health effects under real-world conditions.

Sweeteners May Not Be Biologically Inactive

Sweeteners are found in countless everyday products, including soft drinks, candy, desserts, breakfast cereals, snacks, and some medications. They are commonly promoted as alternatives that provide sweetness with less sugar or fewer calories.

However, growing evidence has linked sweetener consumption with conditions including type 2 diabetes, obesity, and cancer. These associations do not prove that sweeteners directly cause those diseases, and researchers are still working to understand the biological processes that might explain the connections.

One possible factor is the gut microbiome, the enormous community of bacteria and other microorganisms living in the digestive system. These microbes help break down food, produce useful compounds, train the immune system, and influence metabolism. Changes in the number or balance of these organisms may affect health throughout the body.

Despite the widespread use of sweeteners, relatively little research has examined whether they directly affect individual gut bacteria.

Professor Kiran Patil from the Medical Research Council (MRC) Toxicology Unit at the University of Cambridge said: “Most of what we know about the potential impact of sweeteners on our health comes from animal research or from population studies. While these studies have indicated involvement of the microbiome in mediating the effect of sweeteners, it’s difficult to know how sweeteners act in the body — is it through direct interactions with our gut bacteria?”

“Answering this is further complicated by the fact that we rarely ever take sweeteners by themselves — we take them with drinks, in snacks, or even in medication to mask bitterness,” added Dr. Sonja Blasche, a lead author of the study, also the MRC Toxicology Unit.

Testing 39 Sweeteners Against Gut Bacteria

For the study, published in Molecular Systems Biology, Dr. Blasche and her colleagues investigated how artificial and low-calorie sweeteners influence gut bacteria. They also examined whether those effects change when sweeteners are mixed with substances commonly encountered in foods, drinks, and medicines.

The team grew 25 bacterial species separately in the laboratory. The selection included bacteria considered beneficial, neutral, or potentially harmful.

Each species was then exposed to 39 commercially used sweeteners, including both natural and artificial varieties. The researchers monitored how quickly each bacterial culture multiplied and whether its growth slowed or stopped.

About three-quarters of the sweeteners affected the growth of at least one bacterial species. Several reduced or completely halted the growth of bacteria associated with a healthy digestive system.

These findings suggest that some sweeteners are not simply inactive substances that pass through the digestive tract without interacting with the organisms living there.

More Than 100 Unexpected Interactions

People rarely consume a sweetener in isolation. It may appear alongside caffeine in a beverage, flavoring in a dessert, or an active ingredient in a medication.

To recreate some of that complexity, the researchers paired the sweeteners with substances including caffeine, vanillin (vanilla extract), advantame (an artificial sweetener), and eight commonly used drugs.

The team identified more than 100 cases in which a sweetener’s effect changed when another compound was present. The combined effects became stronger in 34 cases and weaker in 68 cases.

This means that the impact of a particular sweetener may depend partly on what else is consumed at the same time.

Antidepressant Combination Stood Out

The most dramatic result involved isosteviol and duloxetine, an antidepressant prescribed to treat depression, anxiety, and certain types of chronic pain.

When used together, the compounds strongly suppressed Roseburia intestinalis and Parabacteroides merdae. Both species are considered important members of the gut microbiome and have been linked to digestive health and metabolic regulation.

Duloxetine is widely used. More than 4.2 million patients in the US received prescriptions for the drug in 2023.

Studying bacteria one species at a time can reveal direct effects, but the human gut is a crowded ecosystem in which microbes constantly interact. To better reflect those conditions, the scientists constructed a simplified microbial community containing all 25 bacterial species.

They allowed the community to develop and then exposed it to different combinations of sweeteners and drugs. The team tracked which species became more abundant, which declined, and whether the community retained its overall variety.

Gut Microbial Diversity Declined

The combination of isosteviol and duloxetine reduced microbial diversity within the synthetic community. Greater diversity is generally considered a feature of a resilient and healthy gut microbiome, although the ideal microbial composition can vary between individuals.

The combination also changed the community’s internal balance by allowing some bacterial species to flourish while others declined.

Additional experiments suggested that these changes increased toxicity toward certain host cells. They also disrupted the activity of other cells involved in inflammation and immune responses.

These results raise the possibility that interactions between sweeteners, medications, and microbes could influence more than digestion alone. However, the simplified laboratory system cannot fully reproduce the complexity of the human body.

Dr. Blasche said: “Sweeteners are often marketed as metabolically neutral, but our study challenges this idea. We found that they can directly affect gut bacteria, particularly when mixed with other compounds such as medication and food additives. These common combinations could have unintended effects on our gut microbiome.”

Human Studies Are Still Needed

The researchers emphasize that the findings should not be interpreted as proof that sweeteners or the tested combinations cause harm in people.

The experiments involved bacteria and cell models under controlled laboratory conditions. In the human digestive system, sweeteners may be absorbed, chemically altered, diluted, or broken down before reaching particular microbes. Diet, genetics, medication use, and the existing composition of a person’s microbiome could also change the outcome.

Future studies will need to determine whether similar interactions occur in humans, what doses would be required, and whether any microbial changes produce measurable effects on health.

Professor Patil, the study’s senior author, added: “Our study suggests that artificial sweeteners don’t just pass through the body passively — they can interact with gut microbes, and these effects can be amplified or altered by other substances like medications. These findings can help guide new studies towards understanding how sweeteners might influence health in unexpected ways.”

The research was funded by the European Union’s Horizon 2020 program and the UK Medical Research Council.

That strategy could be especially valuable in the search for weakly interacting particles, including neutrinos and certain dark matter candidates. These particles are notoriously difficult to detect because they rarely interact with ordinary matter. Building larger detectors and improving their spatial resolution can increase the odds of observing the faint signals they produce, but doing so often makes the instruments more complicated and expensive.

Similar demands apply to calorimeters, the devices used in collider experiments to measure the energy carried by particles.

Why Particle Detectors Are So Complex

Most particle physics experiments need to reconstruct the three-dimensional (3D) paths of elementary particles as they move through large volumes of dense material.

One common detector material is a scintillator. When a charged particle passes through a scintillator, the material gives off tiny flashes of visible light. Scientists use those flashes to determine where the particle traveled and how it interacted with the detector.

To pinpoint the particle’s location, the scintillator is usually divided into a vast number of small active sections. Optical fibers collect the photons produced in each section and carry the light to photomultiplier tubes or silicon photomultipliers, which count the photons.

This approach can be highly precise, but it becomes difficult to scale.

The T2K neutrino-oscillation experiment in Japan, for example, uses a detector with about two tons of sensitive material made from approximately two million cubes and 60,000 fibers. At CERN and the Paul Scherrer Institute, the LHCb and Mu3e experiments reach sub-millimeter spatial resolution by using millions of thin scintillating optical fibers.

These systems demonstrate what segmented detectors can accomplish, but they also reveal a growing problem. As detectors become larger, manufacturing, assembling, and reading out millions of individual components can become a major technological and financial bottleneck.

A Radical New Approach to Particle Tracking

Researchers at ETH Zurich and EPFL are now proposing a very different strategy.

PhD student Till Dieminger, senior scientist Dr. Saúl Alonso-Monsalve, Professor Davide Sgalaberna and colleagues in his group, together with members of the Advanced Quantum Architecture Lab at EPFL in Lausanne led by Professor Edoardo Charbon, developed and tested the first prototype of a detector designed to perform ultrafast, high-resolution 3D particle imaging inside a large, unsegmented block of scintillator material.

Instead of dividing the detector into millions of tiny units, the system uses advanced camera technology to reconstruct where the light originated.

The prototype demonstration and an extensive series of simulations were described recently in Nature Communications.

Turning Light Field Photography Into a Physics Tool

The detector draws inspiration from plenoptic cameras, also known as light field cameras.

Unlike an ordinary camera, which mainly records the intensity of incoming light, a light field camera also captures information about the direction from which the light arrived. This allows it to recover depth and reconstruct a scene in three dimensions.

The technology relies on a micro-lens array (MLA) placed between the camera’s main lens and imaging sensor. Each microscopic lens acts like a tiny camera, recording the same scene from a slightly different angle. When the information from all of these lenses is combined, the system can reconstruct a light field, which describes the intensity, position, and direction of the incoming light.

For particle detection, this ability is particularly useful because the light inside a scintillator may be extremely faint.

When plenoptic cameras are paired with single-photon avalanche diode (SPAD) array sensors, they can detect individual photons and potentially reconstruct particle tracks even when very little light is available. Despite that promise, light field cameras had not previously been explored for particle tracking.

Inside the PLATON Prototype

The new system was developed through the PLATON project, which is funded by the Swiss National Science Foundation.

The ETHZ-EPFL team built a proof-of-concept detector that combines a micro-lens array with a SPAD imaging sensor. The sensor, known as SwissSPAD2, was developed by the EPFL team. Raytrix GmbH designed the MLA and mounted it directly onto the sensor to create the complete plenoptic imaging system.

SwissSPAD2 also provides gated photon detection. This means that the sensor records photons only within defined time windows.

That timing control helps researchers focus on periods when genuine scintillation light is most likely to be present while filtering out random background signals and other spurious counts.

Testing the Detector With Just a Few Photons

The researchers tested PLATON’s spatial resolution in laboratory experiments using light levels ranging from several hundred detected photons down to only five.

They also evaluated whether the prototype could detect electrons and reconstruct their positions inside a block of plastic scintillator. The electrons were produced using a strontium-90 source.

Across the different test conditions, the simulations closely matched the laboratory measurements, giving the researchers confidence that their models accurately describe the detector’s performance.

The results from the first demonstrator have already shaped the team’s plans for the next version of PLATON.

Faster Timing and Greater Sensitivity

The researchers are developing a new SPAD array sensor designed to improve photon detection efficiency and provide sub-nanosecond timing for individual photons.

In the current system, photons are assigned to fixed time windows. In the upgraded version, each detected photon would receive its own precise time stamp.

That added timing information could help the system determine more accurately where each photon came from and improve the reconstruction of particle tracks.

The researchers have also optimized the plenoptic camera to expand its field of view and collect more light. Simulations presented in the paper suggest that these changes should further improve PLATON’s spatial resolution.

AI Reconstructs Hidden Particle Interactions

The team also used simulations to estimate how an upgraded PLATON system could perform when detecting neutrinos.

The simulations incorporated a new image-processing method based on a neural network (NN). The system uses a Transformer architecture adapted from the type commonly used in large language models.

Rather than analyzing words, however, this Transformer examines patterns among the scintillation photons recorded by the detector. It is designed to identify correlations in where and when the photons appear, allowing it to reconstruct the original particle interaction.

The simulations indicate that an unsegmented PLATON detector with a volume of (10x10x10)cm³ could realistically achieve spatial resolution below 1mm.

They also suggest that the system could identify neutrino interactions that produce final-state low-momentum protons with both high purity and high efficiency. In other words, the detector may be able to select the desired events while rejecting many unrelated signals.

Scaling Up to a Cubic Meter

The researchers also considered how the technology might perform in a much larger detector.

Because of limited computing resources, they did not run full neutrino simulations for a one-cubic-meter block of unsegmented scintillator. Instead, they modeled a simplified point-like source of photons.

The simulations suggest that a detector of this size could achieve spatial resolution of a few millimeters, placing it on par with state-of-the-art plastic scintillator detectors.

The result is especially notable because PLATON would achieve this performance without dividing the scintillator into millions of individual pieces.

The authors believe that additional improvements to the optical design and other parts of the system could eventually make sub-millimeter resolution possible in PLATON-type detectors with volumes larger than 1m³.

Potential Uses Beyond Particle Physics

The ETH Zurich researchers believe the technology could eventually be useful far beyond neutrino experiments and particle colliders.

Because PLATON is designed to reconstruct the position of faint light signals in three dimensions, it could improve a wide range of imaging systems.

Dieminger, Alonso-Monsalve and Sgalaberna have already filed three separate patents involving the use of PLATON technology in positron emission tomography (PET). PET is a medical imaging method that tracks radioactive tracers inside the body to reveal activity in organs and tissues.

The patents cover both the scanner design and the image-processing techniques, including the NN developed by Alonso-Monsalve.

Particle physics has a long history of producing technologies that later find broader uses. The world wide web was created at CERN, while proton therapy grew from advances in particle accelerators and radiation physics.

PLATON could become another example of a physics experiment leading to a technology with major scientific and medical applications.

Known as living plastics, these materials contain dormant microbes capable of degrading the surrounding polymer. In a study published in ACS Applied Polymer Materials, scientists developed a version that fully decomposed in six days without producing microplastics.

Zhuojun Dai, a corresponding author on the paper, explains that “the realization that traditional plastics persist for centuries, while many applications, like packaging, are short-lived, led us to ask: Could we build degradation directly into the material’s life cycle?”

Turning Microbes Into a Built-In Disposal System

Some microorganisms naturally produce enzymes that cut long polymer chains into smaller fragments. Since plastics are made from polymers, researchers have been investigating whether these enzymes, or the microbes that produce them, can be embedded directly into plastic materials.

“By embedding these microbes, plastics could effectively ‘come alive’ and self-destruct on command, turning durability from a problem into a programmable feature,” explains Dai.

Earlier living plastic designs often depended on a single enzyme, which limited how efficiently the material could be broken down. To improve the process, Dai, Jin Geng, Dianpeng Qi and colleagues engineered Bacillus subtilis to produce two polymer-degrading enzymes that work together.

The first enzyme cuts the long polymer chains at random points, reducing them into shorter sections. The second then works from the ends of those fragments, breaking them down further into their individual monomer building blocks.

Complete Breakdown in Six Days

The researchers combined dormant B. subtilis spores with polycaprolactone (a polymer common in 3D printing and some surgical sutures). Keeping the bacteria in spore form protected them until the team was ready to begin the degradation process.

The finished living plastic had mechanical properties similar to ordinary polycaprolactone films. It remained strong and functional under normal conditions, suggesting that adding the spores did not significantly weaken the material.

To activate the bacteria, the team added a nutrient broth heated to 122 degrees Fahrenheit (50 degrees Celsius). The spores became active and began producing the two enzymes. Within six days, the plastic had been completely reduced to its basic building blocks.

Because the enzymes worked in sequence, the material did not simply crumble into smaller plastic fragments. The process was efficient enough to prevent microplastics from forming during decomposition.

A Wearable Device That Disappears

To demonstrate a possible real-world use, the researchers made a wearable plastic electrode from the living material. The device worked as intended and then fully degraded within two weeks after activation.

The result suggests that living plastics could eventually be used in products that need to remain durable for a limited time but should not persist after they are discarded.

Expanding the Technology to Other Plastics

The team now hopes to develop a method that activates the bacterial spores in water, where a significant share of plastic pollution accumulates.

Although the experiments focused on a single polymer, the researchers believe the same general strategy could be adapted for other materials, including plastics widely used in disposable products.

The authors acknowledge funding from the National Key Research and Development Program of China, the Shenzhen Medical Research Fund, the National Natural Science Foundation of China, the Guangdong Natural Science Funds for Distinguished Young Scholars, and the Shenzhen Science and Technology Program.