The researchers note that the findings show a relationship, not proof that vitamin D directly reduces tau levels or lowers the risk of dementia.

“These results suggests that higher vitamin D levels in midlife may offer protection against developing these tau deposits in the brain and that low vitamin D levels could potentially be a risk factor that could be modified and treated to reduce the risk of dementia,” said study author Martin David Mulligan, MB BCh BAO, of the University of Galway in Ireland. “Of course, these results need to be further tested with additional studies.”

Long-Term Study Tracks Vitamin D and Brain Biomarkers

The study followed 793 adults who were an average of 39 years old and free of dementia at the beginning. Researchers measured each participant’s blood vitamin D level at the start of the study.

About 16 years later, participants underwent brain scans to evaluate levels of tau and amyloid beta proteins, both of which are considered biomarkers of Alzheimer’s disease. A vitamin D level above 30 nanograms per milliliter (ng/mL) was classified as high, while levels below that threshold were considered low.

Overall, 34% of participants had low vitamin D levels, and only 5% reported taking vitamin D supplements.

Higher Vitamin D Linked to Lower Tau Protein

After accounting for factors such as age, sex and symptoms of depression, the researchers found that higher vitamin D levels were associated with lower levels of tau protein years later.

However, vitamin D levels were not linked to the amount of amyloid beta protein in the brain.

“These results are promising, as they suggest an association between higher Vitamin D levels in early middle-age and lower tau burden on average 16 years later,” Mulligan said. “Mid-life is a time where risk factor modification can have a greater impact.”

Study Limitations and Need for Further Research

One limitation of the study is that vitamin D levels were measured only once rather than tracked over time.

Highlights:

• People with higher vitamin D levels in midlife had lower levels of tau protein later on, a key marker linked to Alzheimer’s disease
• The study shows a link, but it does not prove that vitamin D directly reduces dementia risk
• Researchers found no connection between vitamin D levels and amyloid beta, another Alzheimer’s biomarker
• Further research is needed to confirm these findings and better understand the role of vitamin D in brain health

The study was supported by the National Institute on Aging, National Institute of Neurological Disorders and Stroke, Irish Research Council and Health Research Board of Ireland.

For years, scientists believed that the rapid rise of diverse and complex animals, known as the Cambrian explosion, began around 535 million years ago. This period marked a dramatic shift from simple organisms to a wide variety of more advanced life forms. The new study now indicates that this transformation started at least 4 million years earlier, during the late Ediacaran period.

Lead author Dr. Gaorong Li (Yunnan University at the time of the study, now Museum of Natural History, Oxford University), said: “Our discovery closes a major gap in the earliest phases of animal diversification. For the first time, we demonstrate that many complex animals, normally only found in the Cambrian, were present in the Ediacaran period, meaning that they evolved much earlier than previously demonstrated by fossil evidence.”

Jiangchuan Biota Fossils Show Early Animal Diversity

The fossils were uncovered in the Jiangchuan^[1] Biota in Yunnan Province, where researchers collected more than 700 specimens dating from 554 to 539 million years ago. This site reveals a rich and varied Ediacaran ecosystem, including previously unknown species as well as animals once thought to appear only later in the Cambrian.

Among the most important findings are fossils believed to be the oldest known relatives of deuterostomes, a major group that includes vertebrates such as humans and fish. These discoveries extend the fossil record of this group back into the Ediacaran Period for the first time.

The collection also includes early relatives of starfish and their close counterparts, the acorn worms (the Ambulacraria^[2]). These organisms had U-shaped bodies and were anchored to the seafloor by a stalk. Tentacles near their heads were likely used to capture food.

Co-author Dr. Frankie Dunn (Museum of Natural History, Oxford University) said: “The presence of these ambulacrarians in the Ediacaran period is really exciting. We have already found fossils which are distant relatives of starfish and sea cucumbers and are looking for more. The discovery of ambulacrarian fossils in the Jiangchuan biota also means that the chordates — animals with a backbone — must also have existed at this time.”

Strange Creatures and Transitional Ecosystems

Other fossils include worm-like bilaterian animals (having bilateral symmetry), some showing complex feeding strategies, along with rare specimens thought to represent early comb jellies.

Many of the fossils display unusual combinations of features, such as tentacles, stalks, attachment discs, and feeding structures that could be turned inside out. These combinations do not match any known species from either the Ediacaran or Cambrian periods. “For instance, one specimen looks a lot like the sand worm from Dune!” Dr. Dunn added.

Co-author Associate Professor Luke Parry (Department of Earth Sciences, Oxford University) added: “This discovery is extremely exciting because it reveals a transitional community: the weird world of the Ediacaran giving way to the Cambrian, the following time period where the animals are much easier to place in groups that are alive today. When we first saw these specimens, it was clear that this was something totally unique and unexpected.”

Solving a Long-Standing Evolution Mystery

The findings help answer a long-standing question in evolutionary biology. Previous genetic studies and fossil traces suggested that many animal lineages existed before the Cambrian explosion. However, clear fossil evidence from this earlier period had been largely missing until now.

Exceptional Preservation Reveals Hidden Details

Unlike most Ediacaran fossil sites, which preserve organisms as simple impressions in sandstone, the Jiangchuan Biota fossils are preserved as carbonaceous films. This type of preservation is more commonly associated with famous Cambrian fossil sites such as the Burgess Shale in Canada. It allows scientists to see fine details, including feeding structures, digestive systems, and organs related to movement.

Co-author Associate Professor Ross Anderson (Museum of Natural History, Oxford University) said: “Our results indicate that the apparent absence of these complex animal groups from other Ediacaran sites may reflect differences in preservation rather than true biological absence. Carbonaceous compressions like those at Jiangchuan are rare in rocks of this age, meaning that similar communities may simply not have been preserved elsewhere.”

Years of Fieldwork Lead to Breakthrough Discovery

The fossils were found by a research team at Yunnan University, led by Professor Peiyun Cong and Associate Professor Fan Wei. The group spent nearly a decade searching for diverse Ediacaran animal fossils. Although fossils had previously been discovered in eastern Yunnan, they were limited to algae and did not include animal remains.

Associate Professor Fan said: “After years of fieldwork, we finally found several sites with the right conditions where animal fossils are preserved together with the abundant algae.”

Professor Feng Tang from the Chinese Academy of Geological Science, Beijing, whose earlier work helped guide the research, said: “The new fossils provide the most compelling evidence for the presence of diverse bilaterian animals at the end of the Ediacaran, evidence people have searched for across decades.”

Notes

1. Pronounced ‘jing-choo-an.’
2. Ambulacraria, from the latin ambulacrum, meaning “a walk planted with trees.”

New research led by Craig Walton, a postdoc at the Centre for Origin and Prevalence of Life at ETH Zurich, and ETH Zurich professor Maria Schönbächler shows that these elements must already be available in the right amounts when a planet’s core forms. “During the formation of a planet’s core, there needs to be exactly the right amount of oxygen present so that phosphorus and nitrogen can remain on the surface of the planet,” explains Walton, lead author of the study. On Earth, that appears to have happened about 4.6 billion years ago, giving our planet an unusually fortunate chemical starting point. The result could influence how scientists search for life beyond Earth.

How Planet Core Formation Affects Habitability

Planets begin as bodies of molten rock. As they form, their materials separate by weight. Heavy metals such as iron sink inward and create the core, while lighter material remains above and eventually becomes the mantle and later the crust.

Oxygen levels during this stage are critical. If there is too little oxygen when the core forms, phosphorus bonds with heavy metals such as iron and gets pulled down into the core. Once that happens, it is no longer available in the parts of the planet where life might develop. If there is too much oxygen, phosphorus stays in the mantle, but nitrogen becomes more likely to escape into the atmosphere and be lost.

The Chemical Goldilocks Zone

Using extensive modeling, Walton and his co-authors found that both phosphorus and nitrogen remain in the mantle in large enough amounts only within a very narrow range of moderate oxygen conditions. They describe this as a chemical Goldilocks zone.

“Our models clearly show that the Earth is precisely within this range. If we had had just a little more or a little less oxygen during core formation, there would not have been enough phosphorus or nitrogen for the development of life,” says Walton.

The team also found that other planets, including Mars, formed under oxygen conditions outside this Goldilocks zone. On Mars, that meant more phosphorus in the mantle than on Earth, but less nitrogen, producing difficult conditions for life as we know it.

A New Way to Search for Life Beyond Earth

These findings may change how scientists think about habitability. So far, much of the focus has been on whether a planet has water. Walton and Schönbächler argue that this is not enough.

A planet may have water and still be chemically unfit for life from the very beginning. If oxygen levels were wrong while the core was forming, the planet may never have kept enough phosphorus and nitrogen in the places where life could use them.

Why Sun-Like Stars May Matter Most

Astronomers may be able to estimate these chemical conditions by studying other solar systems with large telescopes. The oxygen available during planet formation depends on the chemical makeup of the host star. Because planets form mostly from the same material as their star, the star’s composition helps shape the chemistry of the entire planetary system.

That means solar systems whose chemistry is very different from ours may be poor candidates in the search for life. “This makes searching for life on other planets a lot more specific. We should look for solar systems with stars that resemble our own Sun,” says Walton.

The findings, published in The Astronomical Journal, come from an international team led by Caleb Cañas of NASA’s Goddard Space Flight Center, with contributions from Carnegie Science’s Shubham Kanodia and others.

A Giant Planet Orbiting a Small Star

TOI-5205 b is about the size of Jupiter but orbits a much smaller star, one that is roughly four times Jupiter’s size and only about 40 percent as massive as the Sun. When the planet passes in front of its star in an event known as a “transit,” it blocks about six percent of the star’s light.

During these transits, astronomers used spectrographs to break the starlight into its component colors. This technique allows them to identify the chemical makeup of the planet’s atmosphere and gain insight into how it formed and evolved alongside its host star.

A Puzzle for Planet Formation Theories

Planets typically form within a rotating disk of gas and dust surrounding a young star. While this process is widely accepted, systems like TOI-5205 b challenge existing models. Massive planets orbiting small, cool stars at close distances are difficult to explain using current theories.

To investigate these unusual systems, Kanodia, Cañas, and Jessica Libby-Roberts of the University of Tampa are leading JWST’s largest Cycle 2 exoplanet program, Red Dwarfs and the Seven Giants. This project focuses on rare worlds like TOI-5205 b, often referred to as GEMS (for giant exoplanets around M dwarf stars).

JWST Detects Unexpected Atmospheric Chemistry

TOI-5205 b was first confirmed in 2023, when Kanodia led follow-up observations based on data from NASA’s Transiting Exoplanet Survey Satellite (TESS). Now, researchers have used JWST to examine its atmosphere in detail for the first time.

After observing three transits, the team encountered an unexpected result. The planet’s atmosphere contains significantly fewer heavy elements compared to hydrogen than Jupiter does. Even more surprising, its metallicity is lower than that of its own host star, making it unlike any giant planet studied so far.

The data also revealed the presence of methane (CH₄) and hydrogen sulfide (H₂S) in the atmosphere.

Heavy Elements May Be Hidden Deep Inside

To better understand these findings, researchers Simon Muller and Ravit Helled at the University of Zurich used advanced models of planetary interiors. Their results suggest that the planet as a whole is about 100 times more metal rich than its atmosphere appears to be.

“We observed much lower metallicity than our models predicted for the planet’s bulk composition, which is calculated from measurements of a planet’s mass and radius. This suggests that its heavy elements migrated inward during formation and now its interior and atmosphere are not mixing,” Kanodia explained. “In summary, these results suggest a very carbon-rich, oxygen-poor planetary atmosphere.”

The GEMS Survey and Future Research

This work is part of the broader GEMS Survey, which aims to study transiting giant planets around M-dwarf stars to better understand their formation, internal structure, and atmospheres. The research team includes Carnegie astronomers Peter Gao, Johanna Teske, and Nicole Wallack, along with former Carnegie postdoctoral fellow Anjali Piette, now at the University of Birmingham.

Additional contributors include researchers from institutions such as Johns Hopkins University’s Applied Physics Laboratory, the Academia Sinica Institute of Astronomy and Astrophysics, Catholic University, the University of Maryland, Caltech, NASA Goddard, the University of St. Andrews, Penn State University, the University of California Irvine, the Tata Institute of Fundamental Research, and the University of Amsterdam.

Correcting for Starspots Improves Accuracy

The team also accounted for interference caused by starspots on the host star. These dark, active regions can distort observations by brightening certain wavelengths and hiding parts of the atmospheric signal.

By correcting for these effects, the researchers improved the accuracy of their measurements. Wallack and Kanodia are now refining this approach in a newer JWST project focused on the same system. Their work could help future studies of planets orbiting active stars produce more reliable results.