New research suggests those early people changed their surroundings far more than scientists once believed.

Computer Models Reveal Early Human Impact

An international team led in part by researchers at Aarhus University used advanced computer simulations to examine how climate, large animals, natural fires, and humans shaped European vegetation during two past warm periods. The team then compared those simulations with extensive fossil pollen data from the same eras. By matching the models with real world evidence preserved in pollen, they were able to estimate how much each factor influenced plant cover.

The results point to a clear conclusion. Both Neanderthals and later Mesolithic hunter-gatherers significantly altered vegetation patterns across Europe, long before agriculture began.

“The study paints a new picture of the past,” says Jens-Christian Svenning, professor of biology at Aarhus University. The project involved experts in archaeology, geology, and ecology from The Netherlands, Denmark, France, and UK.

“It became clear to us that climate change, large herbivores and natural fires alone could not explain the pollen data results. Factoring humans into the equation — and the effects of human-induced fires and hunting — resulted in a much better match,” says Jens-Christian Svenning.

The findings were recently published in PLOS One.

Humans and the Decline of Megafauna

The researchers focused on two specific warm intervals in European history.

The first was the Last Interglacial period around 125,000-116,000 years ago, when Neanderthals were the only humans living in Europe. The second was the Early Holocene, 12,000-8,000 years ago, just after the last Ice Age, when Mesolithic hunter-gatherers from our own species, Homo sapiens, inhabited the region.

During the Last Interglacial, Europe supported a wide range of megafauna. Elephants and rhinoceroses lived alongside bison, aurochs, horses, and deer.

By the Mesolithic period, that picture had changed. Many of the largest animals had vanished or their numbers had dropped sharply. This reflected the broader wave of megafauna losses that followed the global spread of Homo sapiens.

A New View of Prehistoric Europe

“Our simulations show that Mesolithic hunter-gatherers could have influenced up to 47% of the distribution of plant types. The Neanderthal effect was smaller, but still measurable — approximately 6% for plant type distribution and 14% for vegetation openness,” says Anastasia Nikulina.

Human influence showed up in two main ways. One was the use of fire, which burned trees and shrubs. The other was hunting large herbivores, a factor that has often been overlooked.

“The Neanderthals did not hold back from hunting and killing even giant elephants. And here we’re talking about animals weighing up to 13 tonnes. Hunting also had a strong indirect effect: fewer grazing animals meant more overgrowth and thus more closed vegetation. However, the effect was limited, because the Neanderthals were so few that they did not do eliminate the large animals or their ecological role — unlike Homo sapiens in later times,” says Jens-Christian Svenning.

According to Nikulina and Svenning, these findings challenge the idea that Europe was an untouched wilderness before farming began.

“The Neanderthals and the Mesolithic hunter-gatherers were active co-creators of Europe’s ecosystems,” says Jens-Christian Svenning. “The study is consistent with both ethnographic studies of contemporary hunter-gatherers and archaeological finds, but goes a step further by documenting how extensive human influence may have been tens of thousands of years ago — that is, before humans started farming the land,” elaborates Anastasia Nikulina.

AI Simulations and Interdisciplinary Research

Nikulina emphasizes that the project brought together multiple fields, including ecology, archaeology and palynology (knowledge about pollen). The team also developed detailed computer models to simulate ancient ecosystems.

“This is the first simulation to quantify how Neanderthals and Mesolithic hunter-gatherers may have shaped European landscapes. Our approach has two key strengths: it brings together an unusually large set of new spatial data spanning the whole continent over thousands of years, and it couples the simulation with an optimization algorithm from AI. That let us run a large number of scenarios and identify the most possible outcomes,” says Anastasia Nikulina.

Svenning adds that the modeling made one thing clear.

“The computer modeling made it clear to us that climate change, the large herbivores such as elephants, bison and deer, and natural wildfires alone cannot explain the changes seen in ancient pollen data. To understand the vegetation at that time, we must also take human impacts into account — both direct and indirect. Even without fire, hunter-gatherers changed the landscape simply because their hunting of large animals made the vegetation denser,” says Jens-Christian Svenning.

Even with these advances, gaps remain in our knowledge about how early humans influenced their environments.

Nikulina and Svenning note that similar simulations could be applied to other regions and time periods. North and South America and Australia are especially intriguing because they were not inhabited by earlier hominin species before Homo sapiens. That makes it possible to compare more recent landscapes with and without human presence.

“And although the large models paint a broad picture, detailed local studies are absolutely essential to improve our understanding of the way humans shaped the landscape in prehistoric times,” says Jens-Christian Svenning.

In a formal comment published in Global Ecology and Conservation, scientists from Utah State University and Colorado State University argue that a 2025 paper by Ripple et al. overstated how much wolf recovery reshaped Yellowstone National Park’s ecosystem.

“Ripple et al. argued that carnivore recovery produced one of the world’s strongest trophic cascades,” said Dr. Daniel MacNulty, lead author and wildlife ecologist at Utah State University. “But our re-analysis shows their conclusion is invalid because it relies on circular reasoning and violations of basic modeling assumptions.”

The 1500% Willow Growth Claim

The original study reported a 1,500% surge in willow crown volume after wolves returned. That estimate was derived from plant height measurements using a regression model that both calculated and predicted crown volume from height alone.

“Because height was used both to compute and to predict volume,” MacNulty explained, “the relationship is circular — mathematically guaranteed to look strong even if no biological change occurred.”

In other words, the statistical method made the connection appear powerful by design, even if willow growth had not meaningfully changed.

Methodological Concerns and Sampling Bias

The researchers also pointed to several additional concerns:

• The height to volume model was applied to heavily browsed willows with misshapen growth forms, violating the model’s assumptions and inflating apparent increases.
• Willow plots compared between 2001 and 2020 were mostly different locations, making it difficult to separate real ecological change from sampling bias.
• Comparisons with trophic cascades around the world assumed ecological equilibrium, which does not apply to Yellowstone’s still recovering, non equilibrium system.
• Selective photographs and the exclusion of factors such as human hunting further complicated efforts to establish clear cause and effect.

According to the authors, once these issues are addressed, the evidence no longer supports claims of a dramatic ecosystem wide rebound driven by wolves.

“Once these problems are accounted for, there is no evidence that predator recovery caused a large or system-wide increase in willow growth,” said Dr. David Cooper, co author and emeritus senior research scientist at Colorado State University. “The data instead support a more modest and spatially variable response influenced by hydrology, browsing, and local site conditions.”

A More Nuanced View of Predator Effects

The researchers stress that their findings do not dismiss the ecological importance of large carnivores. Instead, they argue that complex food web dynamics require careful analysis and strong evidence.

“Our goal is to clarify the evidence, not downplay the role of predators,” MacNulty said. “Predator effects in Yellowstone are real but context-dependent — and strong claims require strong evidence.”

The new paper helps explain why scientists analyzing the same dataset reached different conclusions. Ripple et al. (2025) described wolf recovery as triggering a powerful trophic cascade. In contrast, Hobbs et al. (2024), who gathered the data during 20 years of field experiments, reported only weak cascade effects.

The analysis focused on three drugs classified as GLP-1 receptor antagonists. Across the board, each medication produced greater weight loss than a placebo. At the same time, researchers found gaps in the evidence, especially regarding long-term health outcomes, side effects, and possible conflicts of interest tied to industry funding.

From Diabetes Treatment to Obesity Therapy

Glucagon-like peptide-1 (GLP-1) receptor agonists were first developed to treat type 2 diabetes and began clinical use in the mid-2000s. In people with diabetes, particularly those with heart or kidney disease, these medications improved blood sugar levels, lowered the risk of heart and kidney complications, supported weight reduction, and reduced the risk of early death.

In recent years, researchers have tested GLP-1 receptor agonists in people with obesity. These drugs copy the action of a naturally occurring hormone that slows digestion and increases feelings of fullness. In the United Kingdom, they are approved for weight management when combined with a reduced calorie diet and exercise in individuals with obesity, or in those who are overweight and have weight-related health conditions.

How Much Weight Loss Do GLP-1 Drugs Produce

Across the three reviews, tirzepatide (Mounjaro and Zepbound), semaglutide (Ozempic, Wegovy, and Rybelsus), and liraglutide (Victoza and Saxenda) all led to notable weight loss over one to two years compared with placebo. The benefits appear likely to continue as long as patients remain on treatment.

• Tirzepatide (administered once weekly) led to an average weight reduction of about 16% after 12 to 18 months. Data from 8 randomized controlled trials (6,361 participants) indicated that this level of weight loss could last as long as 3.5 years, although information on long-term safety remains limited.
• Semaglutide (also injected weekly) produced an average weight loss of roughly 11% after 24 to 68 weeks. Findings from 18 randomized controlled trials (27,949 participants) suggest the effect can persist for up to two years. Participants taking semaglutide were more likely to lose at least 5% of their body weight, but they also experienced higher rates of mild-to-moderate gastrointestinal side effects.
• Liraglutide (a daily injection) showed more modest results, with average weight loss of about 4-5% based on 24 trials (9 937 participants). Even so, more people achieved meaningful weight loss compared with placebo. Evidence beyond two years of treatment was limited.

When it came to major cardiovascular events, quality of life, or death, researchers found little or no difference between the GLP-1 drugs and placebo. Side effects were more common with the medications, particularly nausea and other digestive issues, and some participants discontinued treatment as a result.

“These drugs have the potential to bring about substantial weight loss, particularly in the first year,” says Juan Franco, co-lead researcher from Heinrich Heine University Düsseldorf, Germany. “It’s an exciting moment after decades of unsuccessful attempts to find effective treatments for people living with obesity.”

Concerns About Industry Funding and Access

A large share of the studies included in the reviews were funded by the companies that manufacture the drugs. In many cases, the companies were deeply involved in designing, conducting, analyzing, and reporting the trials. This level of involvement raises concerns about potential conflicts of interest and underscores the need for more independent research.

The authors also stress that broader use of GLP-1 medications must account for social and commercial determinants of health, such as cost, insurance coverage, and overall access. Without careful planning, expanded use could worsen existing health disparities among people living with obesity. High prices currently restrict access to semaglutide and tirzepatide, while liraglutide has become more affordable after its patent expired, allowing generic versions to enter the market. Semaglutide’s patent will also expire in 2026.

Most of the trials reviewed were conducted in middle- and high-income countries. Regions including Africa, Central America, and Southeast Asia were underrepresented or not represented at all. Because body composition, diet, and health behaviors vary widely across populations, researchers emphasize the importance of studying how these drugs perform in diverse global settings.

“We need more data on the long-term effects and other outcomes related to cardiovascular health, particularly in lower-risk individuals,” says Eva Madrid, co-lead researcher from the Universidad de Valparaíso, Chile. “Weight regain after stopping treatment may affect the long-term sustainability of the observed benefits. More independent studies from a public health perspective are needed.”

Long-Term Evidence Needed for Future Guidelines

The reviews conclude that longer-term, independently funded studies are crucial for guiding both medical practice and public health policy. A clearer understanding of sustained benefits and risks will help define the role of GLP-1 receptor agonists in long-term weight management.

Commissioned by the World Health Organization, these findings will inform new WHO guidelines on the use of GLP-1 receptor agonists for obesity treatment.

Their work, published in ChemSystemsChem, offers a fresh way to think about the origin of life on our planet and even raises new possibilities for finding life elsewhere in the universe.

For centuries, people have wondered how life first emerged. Although no one can observe those earliest moments directly, researchers continue to reconstruct what might have happened using clues from chemistry, physics, and geology.

“While many theories focus on the function of biomolecules and biopolymers, our theory instead incorporates the role of gels at the origins of life,” said Tony Z. Jia, professor at Hiroshima University and co-lead author of the paper.

The Prebiotic Gel-First Hypothesis

The researchers propose what they call a “prebiotic gel-first” framework. In this scenario, life’s earliest steps took place inside surface-attached gel matrices, which are sticky, semi-solid materials similar in some ways to modern microbial biofilms. Biofilms are the thin layers of bacteria that commonly grow on rocks, pond surfaces, and even human-made structures.

Using concepts from soft matter chemistry and insights from modern biology, the team suggests that these primitive gels could have created the right physical setting for simple chemical systems to grow more complex, well before the first cells formed.

These gels may have helped solve major challenges faced by early chemistry. By trapping and organizing molecules, they could have increased molecular concentration, held onto useful compounds, and shielded delicate reactions from environmental changes. Within such protected spaces, early chemical networks might have developed proto-metabolic activity and even basic self-replication, laying important groundwork for biological evolution.

“This is just one theory among many in the vast landscape of origin-of-life research,” said Kuhan Chandru, research scientist at the Space Science Center, National University of Malaysia (UKM) and co-lead author of the study. “However, since the role of gels has been largely overlooked, we wanted to synthesize scattered studies into a cohesive narrative that puts primitive gels at the forefront of the discussion.”

Implications for Alien Life and Astrobiology

The idea does not stop with Earth. The researchers suggest that comparable gel-like systems might exist on other planets. These hypothetical structures, described as “Xeno-films,” could function like biofilms but be built from entirely different chemical ingredients available in other environments.

This shift in thinking could expand how scientists search for extraterrestrial life. Instead of focusing only on familiar biological molecules, future missions might also look for organized, gel-like structures that create life-friendly environments.

Testing the Gel Model

The team plans to test their hypothesis in the lab. They intend to examine how simple chemicals under early Earth conditions might have formed gels and to study what properties those gels could have offered emerging chemical systems.

“We also hope that our work inspires others in the field to further explore this and other underexplored origins-of-life theories!” said Ramona Khanum, co-first author of the paper and a former intern at UKM.

The University of Leeds Research Mobility Funding, the Alexander von Humboldt Foundation, the Japan Society for the Promotion of Science, and the Mizuho Foundation for the Promotion of Science supported this research.