The study, published in Nature in 2023, compared genetic material from present day African populations with fossil evidence from early Homo sapiens populations. The result was a model of human evolution that replaces a clean family tree with something more like a network of deeply connected branches.

A More Complex Beginning in Africa

Scientists broadly agree that Homo sapiens originated in Africa. The harder question is how early human groups separated, moved, reconnected, and shaped one another across the continent.

Brenna Henn, professor of anthropology and the Genome Center at UC Davis and corresponding author of the study, said the uncertainty comes from gaps in both fossils and ancient DNA.

“This uncertainty is due to limited fossil and ancient genomic data, and to the fact that the fossil record does not always align with expectations from models built using modern DNA,” she said. “This new research changes the origin of species.”

The work was co led by Henn and Simon Gravel of McGill University. Their team tested several competing ideas about human evolution and migration in Africa, drawing from models proposed in paleoanthropology and genetics. The analysis included genome data from southern, eastern and western Africa.

The Nama Genomes Added a Key Clue

A major part of the study came from 44 newly sequenced genomes from modern Nama individuals in southern Africa. The Nama are an Indigenous population known for carrying unusually high levels of genetic diversity compared with many other living groups.

Researchers collected saliva samples from people in their villages between 2012 and 2015, while participants were going about daily life. Those samples helped the team examine whether human origins fit a single source model or something broader and more interconnected.

The best fitting model suggested that the earliest population split among early humans still detectable in living people happened roughly 120,000 to 135,000 years ago. Before that split, two or more weakly differentiated Homo populations had been exchanging genes for hundreds of thousands of years.

Even after the split, movement and mating continued between these early groups. The researchers describe this as a weakly structured stem, meaning the roots of modern humans were not one isolated population, but a loose set of connected populations with ongoing gene flow.

Not One Branch, But a Network

That network like model may explain human genetic diversity better than older models, according to the authors. Instead of needing to assume major contributions from an unknown archaic hominin population in Africa, the model shows how patterns in modern DNA could have emerged from structure within ancestral human populations themselves.

“We are presenting something that people had never even tested before,” Henn said of the research. “This moves anthropological science significantly forward.”

Co-author Tim Weaver, a UC Davis professor of anthropology who studies early human fossils, said the results shift how scientists should think about older explanations.

“Previous more complicated models proposed contributions from archaic hominins, but this model indicates otherwise,” he said.

Weaver contributed comparative fossil expertise to the study, helping connect genetic models with what early human remains looked like.

What This Means for Ancient Fossils

The model also has consequences for how scientists interpret the fossil record. According to the authors, only 1 to 4% of genetic differentiation among living human populations can be traced to variation between these ancestral stem populations.

Because the early branches continued mixing, they were probably similar in appearance. That means fossils with very different physical traits (such as Homo naledi) are unlikely to represent lineages that directly contributed to the evolution of Homo sapiens, the authors said.

In other words, the roots of humanity may have been geographically and genetically widespread, but not necessarily divided into sharply different human forms. The deeper picture is one of movement, contact, and repeated mixing across Africa.

Later Research Adds More Depth

Work published after the 2023 study has continued to show how important African genomic diversity is for understanding human origins. A 2024 Nature Ecology & Evolution study reported 9,000 years of genetic continuity in southernmost Africa, highlighting the region’s long and unusually deep human population history.

A later Nature study analyzed genomes from 28 ancient southern African individuals dated between 10,200 and 150 years before present. That work found that ancient southern Africans carried genetic variation outside the range seen in living people and identified Homo sapiens specific variants that may shed light on adaptation and evolution within Africa.

Together, these findings strengthen a bigger message: human origins were not a single spark in one place. They were shaped by many populations, deep African diversity, and long periods of connection across the continent.

Additional co-authors of the 2023 study include Aaron Ragsdale, University of Wisconsin, Madison; Elizabeth Atkinson, Baylor College of Medicine; and Eileen Hoal and Marlo Möller, Stellenbosch University, South Africa.

The research was led by neuroscientist Onder Albayram, Ph.D., an associate professor at MUSC and a member of the National Trauma Society Committee. His team focused on the biological processes involved in repairing blood vessels in the brain after injury.

Rising Popularity of Omega-3 Supplements

Interest in omega-3 fatty acids, the key components of fish oil, has been growing rapidly. According to Fortune Business Insights, these supplements are now appearing not only in capsules but also in drinks, dairy alternatives, and snack products.

That surge in popularity does not surprise Albayram. “Fish oil supplements are everywhere, and people take them for a range of reasons, often without a clear understanding of their long-term effects,” he said.

“But in terms of neuroscience, we still don’t know whether the brain has resilience or resistance to this supplement. That’s why ours is the first such study in the field.”

Albayram collaborated with Eda Karakaya, Ph.D., Adviye Ergul, M.D., Ph.D., and several other researchers at MUSC and partner institutions. Among them was Semir Beyaz, Ph.D., at the Cold Spring Harbor Laboratory Cancer Center in New York.

EPA Identified as a Potential Weak Point in Brain Recovery

The team discovered what they describe as a context-dependent metabolic vulnerability. In simple terms, this means that changes in how cells use energy may reduce the brain’s ability to recover under certain conditions. This vulnerability appears to be linked to the buildup of eicosapentaenoic acid, or EPA, one of the main omega-3 fatty acids found in fish oil.

In their experimental models, higher levels of EPA in the brain were associated with weaker repair after injury.

Albayram noted that not all omega-3s behave the same way. Docosahexaenoic acid, or DHA, is well known for its beneficial role in the brain and is a major part of neuronal membranes. EPA, however, follows a different pathway. It is less incorporated into brain structures, and its effects can vary depending on how long it is present and the surrounding biological conditions. Because of this, the long-term impact of omega-3 intake on brain recovery and blood vessel adaptation has remained unclear.

Experiments Link Diet, Brain Biology, and Recovery

To better understand these effects, the researchers used a series of models to connect diet, brain function, and healing. In mice, they examined how long-term fish oil use influenced the brain’s response to repeated mild head impacts. Their focus was on signals related to blood vessel stability and repair.

They also studied human brain microvascular endothelial cells, which form part of the barrier between the brain and the bloodstream. In these cells, EPA, but not DHA, was linked to reduced repair capacity, aligning with the findings from the animal models.

To extend the findings to real-world disease, the team analyzed postmortem brain tissue from individuals diagnosed with chronic traumatic encephalopathy (CTE) who had a history of repeated brain injury.

The researchers described the results as having “implications for precision nutrition, therapeutic strategies and the design of dietary interventions targeting brain injury and neurodegeneration.”

Key Findings From the Study

The study identified several major patterns, which are summarized below along with simplified explanations.

1. EPA-driven neurovascular instability triggers perivascular tauopathy and cognitive decline following TBI.

“In a sensitive brain state modeled in mice, long-term fish oil supplementation revealed a delayed vulnerability. The animals showed poorer neurological and spatial learning performance over time, together with clear evidence of vascular-associated tau accumulation in the cortex, linking impaired recovery to neurovascular dysfunction and perivascular tau pathology,” Albayram said.

2. EPA reprograms cortical transcriptional responses and suppresses angiogenic signaling following traumatic brain injury.

“In the injured cortex, the team observed a coordinated shift in gene programs that normally support vascular stability and repair,” Albayram said. “The pattern included reduced expression of genes tied to extracellular matrix organization and endothelial integrity, alongside broader changes consistent with altered lipid handling after injury.”

3. EPA utilization under permissive metabolic conditions impairs angiogenesis and endothelial integrity, recapitulating post-traumatic brain injury cerebrovascular dysfunction.

Albayram said that in human brain microvascular endothelial cells, EPA did not act as a universal toxin. “Instead, when cells were placed in conditions that encouraged fatty acid engagement, EPA was associated with weaker angiogenic network formation and reduced endothelial barrier integrity, matching key features of the neurovascular repair deficit seen in vivo.”

4. CTE brain reveals neurovascular and fatty acid metabolic reprogramming consistent with EPA-linked vulnerability.

“In postmortem cortex from neuropathologically confirmed CTE cases with a history of repetitive brain injury, the researchers found evidence of disrupted fatty acid balance and broad transcriptional changes affecting vascular and metabolic pathways,” Albayram said. “This human arm was used to provide translational context, asking whether chronic disease tissue shows convergent signatures of altered lipid handling and reduced vascular stability.”

What the Findings Mean for Fish Oil Use

Albayram stressed that the study should not be interpreted as a blanket warning against fish oil. “I am not saying fish oil is good or bad in some universal way,” he said. “What our data highlight is that biology is context-dependent. We need to understand how these supplements behave in the body over time, rather than assuming the same effect applies to everyone.”

The researchers hope their work encourages a more careful look at omega-3 supplementation, both in clinical settings and among the general public. Their experiments focused on a specific scenario, repeated mild brain injury, and used CTE tissue to provide supporting observations rather than direct proof of cause and effect.

“As with any study, there are important boundaries,” Albayram said. “In the human CTE tissue, we can observe patterns, but we cannot prove what drove them. We also cannot capture every variable that shapes omega-3 handling in real life, including overall diet, health status and lifestyle.”

Next Steps in Understanding Omega-3 Effects

The team plans to continue investigating how EPA moves through the body, including how it is absorbed, transported, and distributed. They are especially interested in the mechanisms that control fatty acid movement.

“This paper is a starting point,” Albayram said, “but it is an important one. It opens a new conversation about precision nutrition in neuroscience, and it gives the field a framework to ask better, more testable questions.”

Researchers led by the University of Alaska Fairbanks examined the stomach contents of northern pike collected by the U.S. Fish and Wildlife Service in the Deshka River during the summers of 2021 and 2022. They compared those findings with samples taken from pike in the same river about ten years earlier.

Their analysis showed that pike across all age groups increased their fish consumption as temperatures rose. The change was especially striking among younger fish, with year-old pike consuming 63 percent more fish than before.

The findings were published in the journal Biological Invasions.

“We expect there will be significant warming in the future, and the amount of fish that pike consume is going to increase with it,” said Benjamin Rich, who led the study while pursuing his graduate degree at the UAF College of Fisheries and Ocean Sciences.

Rising Temperatures in Air and Water

The study area has already experienced a steady warming trend. Average summer air temperatures have climbed by about 3 degrees Fahrenheit since 1919, including an increase of 0.8 degrees over the past decade. Water temperatures in the Deshka River, which flows into the Susitna River, have also remained above historical averages in recent years, Rich said.

Looking ahead, scientists expect this warming to continue throughout the 21st century. Models suggest that northern pike could increase their food intake by another 6%-12% by the year 2100.

Warmer Water Boosts Predator Appetite

The growing appetite of pike in the Deshka River reflects patterns seen in other freshwater systems. As water temperatures rise, predator metabolism speeds up, increasing their energy demands and pushing them to feed more aggressively.

This shift is particularly troubling in Southcentral Alaska, where northern pike were introduced illegally and now share habitat with Chinook and coho salmon populations that are already in decline.

Interestingly, the number of Chinook and coho salmon found in pike stomachs dropped over the past decade. Researchers suggest this likely reflects the shrinking salmon populations in the river rather than reduced predation.

Salmon Face Multiple Pressures

Salmon are already under strain from warming conditions, said UAF fisheries professor Peter Westley. More aggressive predation adds another layer of pressure in an already challenging environment.

“We know that invasive species and climate are individually associated with freshwater fish extinctions,” said Westley, a co-author of the study. “Those impacts may be working together into the future.”

Complex Ecosystem Changes

Erik Schoen, a researcher at UAF’s International Arctic Research Center, emphasized the importance of understanding these interconnected effects. Salmon are a key species, but they are only one part of a broader ecosystem influenced by rising temperatures.

“There’s been a lot of work done about how changes in temperature affect salmon directly. That’s really important, but salmon aren’t alone in these rivers,” said Schoen, who also contributed to the paper. “It’s also important to understand how these changes are affecting salmon indirectly through their predators, prey and pathogens.”

Other contributors to the research included Adam Sepulveda and Jeffrey Falke of the U.S. Geological Survey and Daniel Rinella of the U.S. Fish and Wildlife Service.

One bacterium in particular, Morganella morganii, has been linked in several studies to major depressive disorder. Until recently, though, it was unclear whether this microbe contributes to depression, whether depression changes the microbiome, or whether another factor explains the connection.

Researchers at Harvard Medical School have now identified a biological mechanism that strengthens the case that M. morganii can affect brain health. Their findings offer a clearer explanation of how this bacterium may influence depression.

Published in the Journal of the American Chemical Society, the study points to an inflammation-triggering molecule and suggests a possible new target for diagnosing or treating certain cases of depression. It also provides a framework for studying how other gut microbes may shape human health and behavior.

“There is a story out there linking the gut microbiome with depression, and this study takes it one step further, toward a real understanding of the molecular mechanisms behind the link,” said senior author Jon Clardy, the Christopher T. Walsh, PhD Professor of Biological Chemistry and Molecular Pharmacology in the Blavatnik Institute at HMS.

How an Environmental Chemical Triggers Inflammation

The researchers discovered that an environmental contaminant called diethanolamine, or DEA, can sometimes replace a sugar alcohol in a molecule produced by M. morganii in the gut.

This altered molecule behaves very differently from the normal version. Instead of remaining harmless, it activates the immune system, prompting the release of inflammatory proteins known as cytokines, especially interleukin-6 (IL-6).

This chain of events provides a potential explanation that links M. morganii to depression. Chronic inflammation is known to play a role in many diseases and has also been associated with major depressive disorder.

Previous research supports this connection. Studies have linked IL-6 to depression and have also associated M. morganii with inflammatory conditions such as type 2 diabetes and inflammatory bowel disease (IBD).

More research will be needed to determine whether this altered molecule directly causes depression and to understand how many cases might be influenced by this process.

New Possibilities for Diagnosis and Treatment

DEA is commonly found in industrial, agricultural, and consumer products.

“We knew that micropollutants can be incorporated into fatty molecules in the body, but we didn’t know how this occurs or what happens next,” Clardy said. “DEA’s metabolism into an immune signal was completely unexpected.”

The researchers suggest that DEA could potentially be used as a biomarker to help identify certain cases of major depressive disorder.

Their findings also add weight to the idea that depression, or at least some forms of it, may involve the immune system. This raises the possibility that treatments targeting immune responses, such as immune-modulating drugs, could be effective for some patients.

More broadly, the study shows how a bacterial molecule can change human immune function by incorporating a contaminant. This insight may help scientists investigate how other gut bacteria influence immunity and different biological systems.

“Now that we know what we’re looking for, I think we can start surveying other bacteria to see whether they do similar chemistry and begin to find other examples of how metabolites can affect us,” said Clardy.

Collaborative Research Advances Microbiome Science

This breakthrough was made possible by combining expertise from two research groups. The Clardy Lab focuses on the chemistry of small molecules produced by bacteria, while the lab of Ramnik Xavier, the HMS Kurt J. Isselbacher Professor of Medicine at Massachusetts General Hospital, specializes in understanding how the microbiome affects health at a molecular level.

Together, these collaborations have advanced the understanding of how gut bacteria interact with the immune system and influence disease. Their recent work includes:

• Demonstrating how a single bacterium (A. muciniphila), the molecule it produces, the biological pathway it uses, and its effects on the body are connected (protecting against inflammation and increasing sensitivity to cancer immunotherapies).
• Showing that the gut bacterium R. gnavus produces an immune-activating sugar-molecule chain that may explain its link to Crohn’s disease and IBD.
• Discovering that a fatty molecule on the surface of the “strep throat” bacterium S. pyogenes can trigger the immune system to release inflammatory cytokines — helping explain severe immune complications, possible links to autoimmune diseases like lupus, and ways to improve cancer immunotherapies.

That fatty molecule belongs to a group called cardiolipins, which are known to stimulate cytokine release. In the new study, researchers found that when DEA is incorporated into the molecule produced by M. morganii, it begins to behave like a cardiolipin, triggering inflammation.

Authorship, Funding, Disclosures

Sunghee Bang and Yern-Hyerk Shin are co-first authors. Additional authors are Sung-Moo Park, Lei Deng, R. Thomas Williamson, and Daniel B. Graham.

Co-author Xavier is a core institute member of the Broad Institute of MIT and Harvard, where he also directs the Klarman Cell Observatory and the Immunology Program and co-directs the Infectious Disease and Microbiome Program.

This work was funded by the National Institutes of Health (grant R01AI172147) and The Leona M. and Harry B. Helmsley Charitable Trust (2023A004123). The authors also acknowledge the HMS Analytical Chemistry Core, HMS Bio-molecular NMR Facility (formerly East Quad NMR facility; NIH OD028526), and Institute of Chemistry and Cell Biology (ICCB)-Longwood Screening Facility.

A new study from the Department of Meteorology and Geophysics at the University of Vienna provides a clearer picture of where these airborne microplastics come from. Using global measurements and computer models, the researchers estimate emissions from both land and ocean sources. Their key finding is striking: more than 20 times as many microplastic particles are released into the air from land than from the ocean. The study was recently published in Nature.

Sources of Airborne Microplastics

Scientists have long known that microplastics are present in the atmosphere worldwide. These particles eventually settle in distant and isolated locations. They originate from direct sources such as tyre abrasion and textile fibers, as well as from previously contaminated land and ocean surfaces that release particles back into the air.

Until now, the scale of these emissions and the contribution of each source were not well understood. Earlier research often pointed to the ocean as the main contributor, but the new findings challenge that assumption.

Comparing Models With Real-World Measurements

To better understand the problem, researchers Ioanna Evangelou, Silvia Bucci and Andreas Stohl compiled 2,782 individual measurements of atmospheric microplastics from studies conducted around the world. They then compared these real-world observations with results from a transport model that incorporated three different published emission estimates.

The comparison revealed a major issue. The model consistently predicted far more microplastic particles in the air and deposited on the Earth’s surface than were actually observed, sometimes by several orders of magnitude. This gap allowed the researchers to adjust the model and refine emission estimates separately for land and ocean sources, producing more accurate results.

Land Dominates Microplastic Emissions

After recalibrating the data, the team found that emissions from land had been significantly overestimated in earlier models, but even after correction, land remained the dominant source. Ocean emissions were also revised downward.

When asked where most airborne microplastics originate, lead author Andreas Stohl explained: “The now scaled emission estimates show that over 20 times more microplastic particles are emitted on land than from the ocean.” At the same time, first author Ioanna Evangelou noted an important detail: “However, the emitted mass is actually higher over the ocean than over land, which is due to the larger average size of oceanic particles.”

Ongoing Uncertainty and Need for More Data

This research marks an important step toward understanding how microplastics move through the atmosphere and spread globally. However, significant uncertainties remain.

“However, the data situation is still not satisfactory, and there are still major uncertainties. More measurements are needed so that we know how much microplastic comes from traffic and how much from other sources. The size distribution of the particles is also highly uncertain, and thus the total amount of plastic transported in the atmosphere,” summarizes Andreas Stohl, lead author of the study.

Key Findings at a Glance

• Globally distributed measurements of microplastics in the atmosphere were compared with model simulations.
• The comparison showed that the model overestimates the number of measured microplastic particles by several orders of magnitude.
• This is a clear indication that the emission estimates used to date are far too high, especially for land-based emissions.
• The number of microplastic particles emitted from land is more than 20 times higher than the number of particles emitted from the ocean.
• More accurate measurements are needed for more precise emission estimates. In particular, the size distribution of plastic particles is a major source of uncertainty that has not been recorded accurately enough in the measurement data to date.

Two new studies published in the journal Nature reveal a surprising pattern. While the planet gradually cooled over this time, levels of heat-trapping greenhouse gases in the atmosphere declined only slightly.

A Long-Standing Climate Mystery

For more than a century, scientists have known that Earth was significantly warmer about 3 million years ago. Evidence includes fossils of temperate and subtropical forests found in places like Alaska and Greenland, as well as ancient shorelines along the U.S. East Coast from Georgia to Virginia, showing that sea levels were much higher.

However, the reason behind this warm period and the cooling that followed has remained unclear. One major challenge has been the difficulty of accurately reconstructing both global temperatures and greenhouse gas levels from so far back in time.

Searching for the Oldest Ice in Antarctica

The new research comes from the National Science Foundation Center for Oldest Ice Exploration, known as COLDEX, a collaborative effort led by Oregon State University. The team focuses on locating and analyzing some of the oldest ice on Earth.

The studies were led by Julia Marks-Peterson, a doctoral student at OSU, and Sarah Shackleton, who conducted the work as a postdoctoral researcher at Princeton University and is now a professor at Woods Hole Oceanographic Institution. They examined ancient ice recovered from Allan Hills, a unique region along the edge of the East Antarctic ice sheet.

Unlike typical ice core sites, Allan Hills contains ice that has been pushed up and distorted by movement within the ice sheet. This disrupts the original layering, so instead of a continuous timeline, researchers get “snapshots” of climate conditions from different points in the past.

“Those snapshots extend climate records from ice much further than previously possible,” said COLDEX Director Ed Brook, a paleoclimatologist in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “These longer records are also now raising new questions about Earth’s climate evolution and how far back in time we might be able to go with ice core data.”

Ocean Cooling Revealed by Trapped Gases

One study used measurements of noble gases preserved in the trapped air bubbles to estimate changes in ocean temperature over time. These gases provide a global signal of ocean conditions.

The results show that average ocean temperatures have dropped by about 2 to 2.5 degrees Celsius over the past 3 million years. While earlier research has documented cooling at the ocean surface, this study found that the timing of cooling differed between surface waters and deeper layers.

“The noble gases in ice provide a unique way to look at ocean temperature change,” Shackleton said. “Other methods can give you information about ocean temperature at a single site, but this gives a more global view.”

Much of the overall cooling occurred early, beginning around 3 million years ago and continuing for about 1 million years. This period coincides with the formation of large ice sheets in the Northern Hemisphere. In contrast, surface ocean temperatures declined more gradually until about 1 million years ago. Researchers suggest this difference may be linked to changes in how heat moves between the ocean’s surface and its depths.

Greenhouse Gas Levels Show Only Modest Change

Using the same ice samples, Marks-Peterson and her team produced the first direct measurements of carbon dioxide and methane levels spanning the past 3 million years.

Their findings indicate that carbon dioxide levels generally stayed below 300 parts per million during this period. Around 2.7 million years ago, levels were about 250 parts per million and then decreased slightly by roughly 20 parts per million by 1 million years ago. Methane levels remained steady at about 500 parts per billion.

Some earlier estimates based on ancient sediments suggested higher carbon dioxide levels, but results have varied. This highlights the importance of extending ice core records further back in time to improve accuracy.

In contrast, greenhouse gas levels today are much higher. According to the National Oceanic and Atmospheric Administration, carbon dioxide averaged 425 parts per million in 2025, while methane reached 1,935 parts per billion.

More Than Greenhouse Gases Shaped Earth’s Climate

The findings suggest that greenhouse gases alone do not fully explain the long-term cooling trend. Other factors likely played significant roles, including changes in Earth’s reflectivity, shifts in vegetation and ice coverage, and variations in ocean circulation.

“Our hope is that this work will refine our view of past warmer climates and sharpen our understanding of how different elements of the Earth system interact,” said Marks-Peterson.

Even Older Ice May Hold More Answers

The research is already leading to new questions. Scientists involved in COLDEX are continuing to explore older ice samples to push the climate record even further back.

Researchers have recently identified ice that may be as old as 6 million years at the base of one core and are now analyzing these samples. New drilling efforts are also underway to locate additional ancient ice.

Scientists are working to improve methods for reconstructing carbon dioxide levels, studying other gases trapped in the ice, and better understanding how very old ice is preserved. These efforts could help identify new sites for future drilling and further expand the record of Earth’s climate history.

COLDEX is supported by the NSF Office of Polar Programs; the Science and Technology Center Program at the NSF Office of Integrative Activities; and Oregon State University. Fieldwork in Antarctica is supported by the U.S. Antarctic Program and funded by NSF. Ice drilling support is provided by the NSF U.S. Ice Drilling Program and ice sample curation by the NSF Ice Core Facility in Denver, Colorado.