Category: 7. Science

A new method allows scientists to reconstruct carbon dioxide levels and photosynthesis from fossilized tooth enamel.

A surprising new line of evidence is providing fresh insights into Earth’s ancient climate. Fossilized dinosaur teeth reveal that the atmosphere during the Mesozoic era (between 252 and 66 million years ago) contained much higher levels of carbon dioxide than today. This conclusion comes from a study led by researchers at the Universities of Göttingen, Mainz, and Bochum, who examined oxygen isotopes preserved in tooth enamel. Their approach relies on a newly developed technique that offers exciting opportunities for studying Earth’s climate history.

The analysis also showed that global photosynthesis, the process by which plants convert sunlight into energy, was occurring at about twice the rate seen today. According to the researchers, this surge in plant activity likely played a role in shaping the highly dynamic climate that existed during the time of the dinosaurs. The team’s findings were published in the journal PNAS.

To reach these results, the scientists studied dinosaur teeth unearthed in North America, Africa, and Europe from both the late Jurassic and late Cretaceous periods. Tooth enamel, one of the hardest and most resilient biological substances, preserves oxygen isotope signatures that record what dinosaurs inhaled as they breathed. Because the ratio of oxygen isotopes is influenced by atmospheric carbon dioxide and plant photosynthesis, these traces provide a valuable window into both climate conditions and vegetation during the age of the dinosaurs.

Evidence of High CO₂ and Climate Spikes

In the late Jurassic period, around 150 million years ago, the air contained around four times as much carbon dioxide as it did before industrialization – that is, before humans started emitting large quantities of greenhouse gases into the atmosphere.

And in the late Cretaceous period, around 73 to 66 million years ago, the level was three times as high as today. Individual teeth from two dinosaurs – Tyrannosaurus rex and another known as Kaatedocus siberi which is related to Diplodocus – contained a strikingly unusual composition of oxygen isotopes.

This points to CO₂ spikes that could be linked to major events such as volcanic eruptions – for example, the massive eruptions of the Deccan Traps in what is now India, which happened at the end of the Cretaceous period. The fact that plants on land and in water around the world were carrying out more photosynthesis at that time was probably associated with CO₂ levels and higher average annual temperatures.

A Breakthrough for Paleoclimatology

This study marks a milestone for paleoclimatology: until now, carbonates in the soil and “marine proxies” were the main tools used to reconstruct the climate of the past. Marine proxies are indicators, such as fossils or chemical signatures in sediments, that help scientists understand environmental conditions in the sea in the past. However, these methods are subject to uncertainty. By analyzing oxygen isotopes in tooth fossils, the researchers have now developed the first method that focuses on vertebrates on land.

“Our method gives us a completely new view of the Earth’s past,” explains lead author Dr Dingsu Feng at the University of Göttingen’s Department of Geochemistry. “It opens up the possibility of using fossilized tooth enamel to investigate the composition of the early Earth’s atmosphere and the productivity of plants at that time. This is crucial for understanding long-term climate dynamics.” Dinosaurs could be the new climate scientists, according to Feng: “Long ago their teeth recorded the climate for a period of over 150 million years – finally we are getting the message.”

Reference: “Mesozoic atmospheric CO₂ concentrations reconstructed from dinosaur tooth enamel” by Dingsu Feng, Thomas Tütken, Eva Maria Griebeler, Daniel Herwartz and Andreas Pack, 4 August 2025, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2504324122

The study was funded by the German Research Foundation (DFG) and by the VeWA consortium as part of the LOEWE programme of the Hessisches Ministerium für Wissenschaft und Forschung, Kunst und Kultur.

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Sharks without teeth might sound like the stuff of dreams to swimmers and surfers. Now a new study has found that ocean acidification could leave the apex predators without their critical survival weapon.

Shark jaws carry several rows of teeth and new ones quickly push forward to replace losses. However, rapidly acidifying oceans are damaging shark teeth and could speed losses past replacement rates. Sharks with bad teeth could struggle to feed themselves efficiently, “potentially affecting shark populations and marine ecosystem stability”, the study said.

Ocean acidification is caused by rapid carbon dioxide absorption creating a chain reaction that lowers pH levels. Projections suggest oceans could be far more acidic by the year 2300, falling from a current average pH of about 8.1 to 7.3, a change that will have “profound implications for marine organisms”, the study said.

To test acidification effects, researchers kept 60 freshly fallen shark teeth in artificial seawater tanks, one matching the current ocean average pH of 8.1, another with the projected 7.3 pH. The teeth, safely collected from a German aquarium, had already been naturally discarded by six male and four female blacktip reef sharks.

After eight weeks, teeth in the more acidic tank suffered about twice as much damage, said Maximilian Baum, the study’s lead author and a researcher working with Germany’s Heinrich Heine University’s Institute for Zoology and Organismic Interactions. Effects included “increased root corrosion … and altered serration”, he said.

Dental stress would add to sharks’ other problems, which include prey shortages caused by overfishing.

Reducing human-caused CO2 emissions is vital to mitigate ocean acidification. Previous research has found acidification damages denticles, a toothy scale on sharks’ skin.

Even moderate drops could affect more sensitive shark species, such as those that use fewer rows of teeth or have slower replacement rates, said Baum.

“I think there will be effects on the teeth of ocean predators in general when they are highly mineralised structures like we have in sharks,” he said.

Previous studies have shown that acidification harms shells, corals and mussels, “and that was also the reason why we did this study, to show us the effects on larger predators”.

More optimistically, Baum believes sharks may adapt by increasing tooth replacements and improving strengthening and repair.

Lisa Whitenack, a professor at Pennsylvania’s Allegheny College who is a shark tooth expert and not part of the study team, said the new research added to initial findings on shark teeth and acidification. She too suggested tooth replacement may keep pace with acidification losses and added that corroded teeth may still be effective.

“It will be interesting to see in future studies if the damage to teeth seen in studies like this one results in a functional effect on a tooth’s ability to do its job … [and if] damaged teeth can still cut or puncture prey.”

Spectroscopy is one of the most widely used techniques for studying the structure of atoms. This technique is based on the principle that electrons absorb or emit energy when they move between energy levels in an atom. Each element has a unique set of wavelengths of light that are emitted or absorbed due to these transitions. This is known as the atomic spectrum.

“High-resolution, broadband spectroscopy is essential for precision measurements in atomic physics and the search for new fundamental interactions,” explains Razmik Aramyan, PhD student in the group of Prof. Dr. Dmitry Budker and main author of the paper. “But progress is often hindered by the difficulty of measuring complex atomic spectra, mainly due to two technical limitations: the difficulty of properly distinguishing the signals emitted by the sample and the limited range of wavelengths that instruments can detect.” To overcome those limitations, Aramyan and his collaborators have applied and further developed a method known as dual-comb spectroscopy (DCS), which allows to measure atomic spectra at a wide band of electromagnetic frequencies with high resolution and high sensitivity.

The DCS is based on the optical frequency comb technique, for which the Nobel Prize in Physics was awarded in 2005. Optical frequency combs are specialized lasers that measure exact frequencies of light. In DCS, two of these combs are used in coherent mode, enabling more accurate measurements of the sample’s spectrum than conventional methods.

In order to detect weak signals with high precision—one of the challenges of DCS—the group also implemented multiple photodetectors to improve what is known as the signal-to-noise ratio. This combination made it possible to clearly read the experimental data and determine the different wavelengths of the spectrum. “This study introduces an enhanced multichannel DCS approach that combines a photodetector array with a novel scheme for resolving frequency ambiguities, enabling ambiguity-free, high-signal-to-noise-ratio broadband measurements”, summarizes Aramyan.

This is the first step toward implementing “Spectroscopy 2.0”, an international project that aims to develop what is known as a “massively parallel spectroscopic tool”: one that can perform a large number of spectroscopic measurements simultaneously. This tool will be used to perform spectroscopy of dense atomic and molecular spectra under intense magnetic fields.

First successful application: the spectrum of samarium vapor

DCS is particularly well suited to filling gaps in atomic data, as the current publication confirms. Thanks to their innovative approach, Aramyan and colleagues were able to record the spectrum of samarium vapor at different temperatures and analyze the spectral behavior at different samarium concentrations. When comparing their results with existing data sets, they found spectroscopic lines that were previously unknown.

“We have discovered several previously undescribed samarium absorption lines. This illustrates the potential of our method to uncover previously unknown atomic properties. It opens up promising possibilities for massively parallel spectroscopy, for example for the spectroscopy of atoms in pulsed, ultra-high magnetic fields,” concludes Aramyan.