Bear teeth break free – Researchers discover the origin of unusual bear dentition

Staatliche Naturwissenschaftliche Sammlungen Bayerns

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Ursus deningeri, an early cave bear, had a larger third molar (right) compared to the second molar (center) than would be expected based on the model. (Natural History Museum Vienna).

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Credit: Photo: Anneke H. van Heteren

Mammalian teeth show an astonishing diversity that has developed over almost 225 million years. One approach to describing the development of mammalian teeth is the so-called “Inhibitory Cascade Model”, short ICM. The ICM describes the growth pattern of molars in the lower jaw. According to the model, the following applies to many mammals: The front molars in the lower jaw influence the growth of all the teeth behind them. Certain molecules inhibit or activate tooth growth in the animal's dentition according to the same pattern. Which molars become small or large depends on the size of the first molar, which depends on the animal's diet. In carnivorous mammals, the first molar is usually larger than the third. In herbivores, it is the other way around: the first molar is small, while the third is large.

This is not the case in modern bears, whose tooth development does not follow the ICM pattern. In almost all modern bears – regardless of their diet – the second molar is the largest of all molars. SNSB zoologist PD Dr. Anneke van Heteren and her doctoral student, Stefanie Luft, investigated the origin of this phenomenon. They searched for clues in the evolutionary history of bears and actually found two breaks in bear history, indicating when and in which bear species tooth development deviates from the general pattern. For their work, the researchers compared the jaws of fossil and modern bears with the ICM model – going far back in bear history, the oldest jaw examined dates from the Miocene and is at least 13 million years old. The zoologists identified the first fundamental break in tooth development around 3.6 million years ago. In Ursus minimus – the common ancestor of most modern bears – the second molar grew disproportionately large. The second break occurred somewhat later, around 1.25 to 0.7 million years ago, in Ursus deningeri, the predecessor of the classic cave bear. In this species, the third molar grew larger than expected according to the model.

"Apparently, the balance of chemical compounds that inhibit or activate the growth of the different molars shifted during these periods. These shifts are probably associated with dietary adaptations of bears in the course of their evolution. On their way from carnivores to omnivores or herbivores, bears adapted to a changed food spectrum, but without following the ICM pattern. Their spectrum still ranges from pure carnivores to pure herbivores, with most bears today being omnivores," says PD Dr. Anneke van Heteren, responsible for the mammal collection at the Bavarian State Collections of Natural History (SNSB).

The researchers explain the two breaks in the tooth development model by the environmental changes during the evolutionary history of bears. The first break between the early and late Pliocene correlates with climate changes that led to changes in habitats from subtropical rainforests to shrubland and steppes. The second break occurred between the late Pliocene and the middle Pleistocene and is associated with the development of extensive grasslands and a cooling of the climate.

In this young cave bear, the third molar is just erupting, its size determined by the second tooth. Cave bears were herbivores and have second and third molars that are approximately the same size (Bavarian State Collection of Zoology)

The polar bear has a second molar that is only slightly larger than the first. Although the polar bear is a carnivore, it is descended from the omnivorous brown bear. (Bavarian State Collection of Zoology)

Credit

Photo: Katja Henssel, SNSB

In this subadult sloth bear Melursus ursinus, the first and second molars (second and third from the left) are approximately the same size. Sloth bears are partially insectivorous and have relatively small third molars (ZMB_Mam_44143, Museum of Natural History Berlin).

Credit

Photo: Anneke H. van Heteren

Journal

Boreas

DOI

10.1111/bor.70044 

Subject of Research

Animals

Article Title

Fossil bears break free from inhibitory cascade constraints at least twice (Ursus minimus and Ursus deningeri) caused by dietary adaptations

 

Nanoscale structure turns peat into a powerful candidate for sustainable fuel cells

Estonian Research Council

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Schematic representation of the catalyst material featuring hierarchical porosity, including interconnected micro-, meso-, and macropores. The pore curvature is highlighted to illustrate its influence on surface accessibility and catalytic performance.

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Credit: Rutha Jäger

Electrochemists Rutha Jäger of the University of Tartu and Eneli Härk of the Helmholtz-Zentrum Berlin mapped the atomic structure of this iron-nitrogen-carbon catalyst, demonstrating how it might compete with costly precious metals in fuel cell technology. The article “Small-Angle X-ray Scattering Monitoring of Porosity Evolution in Iron–Nitrogen–Carbon Electrocatalysts” was published in ACS Nano, a ranked in the top 5 in the Nanoscience & Nanotechnology and the Multidisciplinary Materials Science.
Fuel cells, which convert the chemical energy of hydrogen directly into electricity, producing only water as a byproduct, are emerging as a key technology for a climate-neutral energy system. However, the main obstacle is the high cost of electrocatalysts, which are usually based on the precious metal platinum. Researchers are currently exploring catalyst options using common metals rather than precious ones, which could dramatically lower expenses without sacrificing performance. However, these catalysts have a key limitation: the oxygen reaction occurs slowly through multiple stages and can generate hydrogen peroxide as a byproduct along the way, causing harm to fuel cell parts.
Carbon Structures Like an Anthill
Rutha Jäger, Associate Professor in Physical and Electrochemistry at the University of Tartu, described their research approach. The team investigated five iron-nitrogen-carbon catalysts produced under different conditions, each using well-decomposed Estonian peat as the precursor material. The key question driving their investigation was why materials derived from nearly identical precursors exhibited vastly different levels of activity and selectivity.
According to Dr. Jäger, carbon-based materials display extraordinary variation in structure. High-performing fuel cell catalysts require extensive porosity, creating an interconnected maze of passages analogous to an anthill's tunnel architecture. These channels allow hydrogen and oxygen molecules to travel toward catalytically active sites for water formation, with the resulting water departing via the same pathways. Variables like pore size and wall dimensions may either promote or limit the material's catalytic activity and selectivity.
Tracing the Optimal Carbon Networks
Dr. Eneli Härk, an electrochemist from Helmholtz-Zentrum Berlin, and her team utilized (anomalous) small-angle scattering techniques (ASAXS/SAXS) at the BESSY II third-generation synchrotron radiation facility, working alongside specialists from the German National Institute for Metrology (PTB). This small-angle X-ray scattering method delivers precise, quantitative insights into pore curvature and the relationship between pore dimensions and wall thickness - characteristics that are notoriously challenging to measure. Dr. Härk explained that the researchers mapped essential structural features of the catalysts, including hierarchical porosity, structural irregularities, and the spacing between active sites nested within the pores. By examining catalysts across the entire spectrum from micropores to macropores, they uncovered the characteristics of the otherwise hidden nanostructure.
From Structure to Performance
The investigation pinpointed 13 structural parameters, including porosity, structural irregularities, and pore curvature, and follow-up oxygen reduction reaction experiments allowed the researchers to connect these structural characteristics with catalytic effectiveness. Revisiting the anthill comparison: small-angle scattering creates a comprehensive blueprint of the anthill's architecture, while electrochemical testing reveals how molecules, like "ants," navigate through its tunnels. A significant discovery was that oxygen reduction to water works most efficiently when pore curvature reaches a minimum of three nanometers, which helps prevent the unwanted generation of hydrogen peroxide.
Bridging Structure and Sustainability
While researchers previously understood the connection between electrochemical performance and multi-level porosity, Dr. Eneli Härk and Dr. Rutha Jäger's ASAXS-based investigation now illuminates the specific structural details that govern these reactions, creating fresh opportunities for catalyst innovation. Equally significant, the team emphasized, is the practical pathway from peat bog to fuel cell: well-decomposed peat serves as an effective source for producing eco-friendly, non-precious metal carbon catalysts. According to Dr. Härk and Dr. Jäger, Estonia's abundant peat reserves thus offer considerable potential as a feedstock for advanced functional materials.

ACS Nano 2025, 19, 46, 40072–40084 https://doi.org/10.1021/acsnano.5c14955

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Journal

ACS Nano

DOI

10.1021/acsnano.5c14955 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Small-Angle X-ray Scattering Monitoring of Porosity Evolution in Iron–Nitrogen–Carbon Electrocatalysts

Article Publication Date

13-Dec-2025

 

More sustainable food and less waste by moving microalgae beyond being niche ingredients

European Science Communication Institute gGmbH

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Single-production and extraction (top) vs multi-product biorefinery (bottom)

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Credit: European Science Communication Institute gGmbH

With food systems under pressure from climate change, geopolitical instability, and supply chain vulnerabilities, the EU is driving innovation toward more sustainable, resilient, and local production models. Microalgae have emerged as a promising resource for producing ingredients across food, feed, and other consumer goods.  

“Algae play a key role in advancing a bio-based circular economy. They provide sustainable alternatives for producing food, feed, and bio-based chemicals for example, while helping to reduce land-use pressure and tackle global challenges, such as climate change, ultimately contributing to the EU’s sustainable growth and competitiveness,” says Monica Padella, a project officer at the Circular Bio-based Europe Joint Undertaking (CBE JU), which funds projects aimed at making Europe’s industries circular and bio-based.   

Despite technical advances, the growing microalgae industry in Europe mostly relies on freshwater, added nutrients, and limited product output per biomass. These constraints keep costs high and limit the wider adoption of microalgae-based alternatives to conventional products.  

To overcome these challenges, academic and industry experts co-created the research project ALLIANCE to produce ‘more with less’. The CBE JU-funded project started in September.  

“The name ALLIANCE is not just our project’s acronym, but our spirit. It represents our systemic and collaborative approach,” says project coordinator Iago Teles from Wageningen University in the Netherlands. 

With an interdisciplinary and joint approach, the ALLIANCE partners aim to develop optimised multi-product biorefineries for the microalgae Spirulina, Galdieria, Chlorella and Nannochloropsis, to convert single algae biomasses into multiple products and increase the utilisation efficiency of algae biomass. 

“A microalgae multi-product biorefinery is a known but difficult concept to realise,” says Iago Teles. “Our biggest strength is the broad ground of expertise, knowledge, applications and products we cover, from food, to feed, and biobased chemicals.”  

The goal is to develop ingredients for foods, beverages, aquaculture feed, cell growth media for lab-cultured meat, and biological pest control from microalgae within four years.  

To further maximise resource efficiency in the manufacture of these products, the ALLIANCE partners are also optimising microalgae cultivation. They develop circular production models, following the “Reduce, Reuse, Recycle, and Recover”- 4Rs principle to: 

• Reduce the need to add new nutrients to microalgae production by automated production and adjusting culture media 

• Reuse output-water from previous microalgae production cycles or from the brewery, food processing, hydroponic agriculture and aquaculture industries 

• Recycle and recover nutrients present in industrial output-waters as input nutrients for microalgae cultivation  

“ALLIANCE was designed following a value-chain approach, in which all our 19 partners contribute in a unique way to bring 4 different production pipelines, 19 ingredients, and 12 product prototypes into reality. The field of microalgal biotechnology needs such showcases to demonstrate its contribution to a transition to a circular and biobased industry,” explains Prof. Maria Barbosa from Wageningen University and scientific coordinator of the project. 

From establishing multi-product biorefineries, to improving water reuse and nutrient recycling, the experts behind ALLIANCE will optimise every step of the microalgae value chain. This will maximise resource usage and minimise waste generation. With lower costs for both consumers and the environment, the ALLIANCE partners will make sustainable microalgae-based products more affordable and more widely accessible. 

Simple gel jelly beads on a liquid surface reveal secrets of slow earthquakes

Researchers at The University of Osaka reproduced multiple statistical characteristics observed in slow earthquakes, through simple experiments with floating soft gel jelly beads

The University of Osaka

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Cross section of a subduction zone and the source regions of slow earthquakes

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Credit: Yuto Sasaki

Osaka, Japan — Slow earthquakes have been discovered to exhibit anomalously slow, long-lasting and small slips, adjacent to regular earthquakes where we sometimes feel catastrophic vibration (Fig. 1). However, no one knows the reason why slow earthquakes show such strange characteristics. In a study published in a scientific journal Nature Communications, researchers at The University of Osaka succeeded in experimentally reproducing the multiple features of slow earthquakes in the lab (Fig. 2) and suggested the grain-scale origin of them based on their direct observations.

More than 20 years after the discovery of slow earthquakes, which cause weak or no perceptible vibration but associate with slow slip for about a year at maximum, the unified explanation for the characteristics of slow earthquakes does not exist. Up to now, most experimental studies that reproduced slow earthquakes have focused only on the slowness of fault slip. However, what makes slow earthquakes most distinct from regular earthquakes are rather their statistical features revealed through seismic observations (Fig. 2 upper panels). These statistical characteristics of slow earthquakes, however, had rarely been reproduced or explained in laboratory experiments.

“Slow earthquakes have traditionally attracted attention mainly for their slow slip rate, but the statistical properties of their duration and recurrence relative to earthquake magnitude have so far been addressed only in a few limited experiments,” says a study author Yuto Sasaki. “Needless to say, experiments using actual rocks and natural fault grains are of great importance; however, we realized a necessity of simpler physical equivalent, which enables us to directly observe internal structures during deformation. This is a major advantage of our experimental system, as such direct internal observation is usually very difficult in rock-deformation experiments.”

The researchers have prepared very simple “gel jelly beads raft” (Fig. 3). As the fault region of slow earthquakes is expected rich in fluid and soft grains, they conceived its physical analog of soft gel jelly beads in a liquid solution. “This table-top experimental system is available even in your home, but it shows a surprising variety of behaviors and offers us a wealth of fascinating clues about slow earthquakes underground,” says Sasaki. “If you put rigid glass beads into a dry cup and mix it slowly, you can feel intermittent and fast scratches. Actually, these scratch events show the statistics similar to regular earthquakes.” However, the mixture of gel jelly beads and a liquid solution shows significantly different features with longer and smaller events, as with slow earthquakes (Fig. 2 lower panels). “You can feel sluggish, intermittent slide by mixing bubble tea, but the two phenomena seem to be fundamentally different.”

In contrast to dry rigid beads, soft wet beads are inefficient in transmitting force and deformation. This property potentially induces longer and isolated small slips. “In retrospect, this experimental system seems to have been well suited for studying fault systems of slow earthquakes, while our prior target was deeper part of tectonic plate,” says Sasaki. “We expect the similar experimental report from high temperature and pressure experiments using rock and fault material.”

Slow earthquakes often occur adjacent to the source regions of regular, destructive earthquakes (Fig. 1). “Based on the results, observed slow earthquake statistics could be interpreted as fault conditions,” says Sasaki. This would contribute to probabilistic assessments of earthquakes. Moreover, the longstanding mystery of the mechanisms underlying slow earthquake occurrence is expected to be further addressed not only through laboratory experiments but also through observational studies and geological analyses. “This experimental result will serve as a starting point for further contributions from a wider range of fields, ultimately advancing our understanding of slow earthquakes and enabling better assessment of their influence on conventional, destructive earthquakes,” says Sasaki.

Since the experimental setup used in this study is simple, the observed results can also represent general characteristics of the mixture of soft beads and liquid. “By analyzing the detailed relationship between microscopic bead rearrangements and macroscopic slips, fundamental aspects of sheared soft-matter systems can be revealed, as well as the origin of characteristic features of slow earthquakes. Nothing excites me more than realizing that tabletop experiments in soft matter can unlock the mysteries of both fundamental soft-matter physics and geological-scale phenomena,” says an author Hiroaki Katsuragi.

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The article, “Origin of slow earthquake statistics in low-friction soft granular shear,” was published in Nature Communications at DOI: https://www.doi.org/10.1038/s41467-025-65230-z

Geophysical observations (upper) and experimental results in this study (lower)

Credit

After Sasaki & Katsuragi (2025) Nature Communications

About The University of Osaka

The University of Osaka was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world. Now, The University of Osaka is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.

Website: https://resou.osaka-u.ac.jp/en

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Journal

Nature Communications

DOI

10.1038/s41467-025-65230-z 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Origin of slow earthquake statistics in low-friction soft granular shear

Article Publication Date

1-Dec-2025