Above 45 kg, the researchers found evidence for decreasing abundance with increasing size, a pattern that aligns with the ecological ‘rule of metabolic scaling’, whereby larger species have lower population densities compared to smaller ones. A deviation from the predicted ecological pattern was that mammals between ~15 and 45 kg were far less numerous than expected, both in living and fossil communities. They interpreted this as a signature of savanna habitats (where monkeys and small forest-living antelopes are rare).

The big surprise came when the researchers examined how size-abundance distributions changed over time. They discovered that earlier communities, older than ~4 million years ago, had a considerably higher number of large-sized individuals and a greater proportion of total biomass in larger size categories, than did younger communities. The high abundance of large individuals in these fossil African communities — with some individual elephants reaching sizes over 10 tons — is unparalleled in ecosystems today. Since that time, there has been a gradual loss of large-sized individuals from the fossil record, reflecting the long-term decline of late Pliocene and Pleistocene large mammal diversity, and resulting in the impoverished and ‘miniaturized’ communities we know today.

The study confirms recent work arguing for the deep-time antiquity of African megafaunal losses and challenging the idea that the decline of African megafauna was primarily driven by human activities. While the spread of humans across the globe during the late Pleistocene and Holocene (the last ~100,000 years) coincided with major extinction of many large animals, the research supports the idea that megafaunal losses in Africa began much earlier, around 4 million years ago, and long before humans learned to engage in efficient hunting. Instead, the study highlights environmental factors, such as the long-term decrease in global temperatures and the expansion of tropical grasslands, as potential drivers of megafaunal extinctions.

The study also found that the loss of large individuals and the restructuring of biomass distributions in African large mammal communities could have been linked to decreases in primary productivity. Using an established relationship between the types of mammalian tooth shapes (morphological traits) and plant productivity (net primary productivity) today, the researchers calculated productivity for African communities in the past. They found an approximately two-thirds decrease in productivity since the Late Miocene (> 5 million years ago), a pattern observed globally, and that could have significantly diminished the carrying capacity of large mammal communities, leading to reduced diversity and accelerated extinction of large species.

The research opens new avenues for understanding the dynamics of ecosystems and the complex interactions between individuals, species, and their environment. By analyzing fossil abundance data and incorporating size-based approaches, scientists can gain valuable insights into the ecological dynamics underlying extinction.

The publication of this scientific paper marks a significant milestone in our understanding of African megafaunal extinctions and the restructuring of ecosystems over geological time scales. Bibi and Cantalapiedra’s findings have the potential to inform conservation efforts and enhance our ability to predict and manage the consequences of biodiversity loss in the face of environmental change.

In the new study, led by Imperial College London and published today in Science, researchers ranked 90% of global net-zero greenhouse gas emissions pledges as providing low confidence in their full implementation.

The researchers recommend nations make their targets legally binding and back them up with long-term plans and short-term implementation policies to increase the likelihood of avoiding the worst impacts of climate change.

Lead researcher Professor Joeri Rogelj, director of research for the Grantham Institute at Imperial, said: “Climate policy is moving from setting ambitious targets to implementing them. However, our analysis shows most countries do not provide high confidence that they will deliver on their commitments. The world is still on a high-risk climate track, and we are far from delivering a safe climate future.”

Assigning confidence

Climate goals set out in the Paris Agreement include keeping temperature rises well below 2°C above the average temperature before the industrial revolution and ideally below 1.5°C. The main way to achieve this is the reach ‘net-zero’ greenhouse gas emissions as soon as possible, where any remaining emissions are effectively offset.

Most countries have set net-zero goals and Nationally Determined Contributions (NDCs) — non-binding national plans proposing climate actions. Taking these plans at face value, and assuming they will all be fully implemented, gives the world a chance of keeping warming to 1.5-2 degrees C. But taking current policies only, with no implementation of net-zero pledges, means models predict temperature rises could be as much as 2.5-3 degrees C by 2100, with warming still increasing.

To reduce the uncertainty in which of these scenarios is likely to happen, the team, including researchers from the UK, Austria, USA, Netherlands, Germany, and Brazil, assigned a ‘confidence’ to each net-zero policy. They assessed 35 net zero targets, covering every country with more than 0.1% of current global greenhouse gas emissions.

The confidence assessment was based on three policy characteristics: whether the policy was legally binding, whether there was a credible policy plan guiding implementation, and whether short-term plans would already put emissions on a downward path over the next decade.

Based on this, policies were given ‘higher’, ‘lower’ or ‘much lower’ confidence of being fully implemented. Some regions scored highly, including the European Union, the United Kingdom and New Zealand, but around 90% scored ‘lower’ or ‘much lower’ confidence, including China and the US, which together account for more than 35% of current emissions.

Modelling emissions

From this assessment, the team modelled five scenarios of future greenhouse gas emissions and resulting temperatures. These were: considering only current policies (the most conservative scenario); only adding in policies that have a high confidence of being implemented; adding policies with high and low confidence; adding all policies regardless of confidence as if they are implemented; and a scenario where all policies are fully implemented and all NDCs are met (the most forgiving scenario).

The most conservative scenario had the largest uncertainty, with a range of 1.7-3°C and a median estimate of 2.6°C. The most optimistic scenario has a range of 1.6-2.1, with a median estimate of 1.7°C. This might suggest that, if all net-zero policies are fully implemented, the Paris Agreement goals are withing reach. However, with so many policies ranked in the low-confidence end of the scale, this would be wishful thinking in absence of further efforts.

Co-author Taryn Fransen, from the World Resources Institute in Washington DC, and the Energy and Resources Group at the University of California-Berkeley, said: “Climate change targets are by their nature ambitious — there’s no point in setting a target for a foregone conclusion. But implementation must follow.”

Catalysing action

Only twelve out of 35 net zero policies are currently legally binding, and the researchers say increasing this number would help ensure the policies survive long-term and catalyse action. Countries also need clear implementation pathways for different sectors, outlining exactly what changes are needed and where the responsibility lies.

Co-author Dr Robin Lamboll, from the Centre for Environmental Policy at Imperial, said: “Making targets legally binding is crucial to ensure long-term plans are adopted. We need to see concrete legislation in order to trust that action will follow from promises.”

The team included researchers from Imperial College London (UK) the International Institute for Applied Systems Analysis (Austria), the World Resources Institute (US), the University of California-Berkeley (US), the Netherlands Environmental Assessment Agency, the Institute for Environmental Studies (Netherlands), the NewClimate Institute (Germany), the Copernicus Institute of Sustainable Development (Netherlands), and the Universidade Federal do Rio de Janeiro (Brazil).

Emil Sierda, who was in charge of conducting the experiments at Radboud University: ‘A few years ago we had this crazy idea to build a quantum simulator. We wanted to create artificial molecules that resembled real molecules. So we developed a system in which we can trap electrons. Electrons surround a molecule like a cloud, and we used those trapped electrons to build an artificial molecule.’ The results the team found were astonishing. Sierda: ‘The resemblance between what we built and real molecules was uncanny.’

Changing molecules

Alex Khajetoorians, head of the Scanning Probe Microscopy (SPM) department at the Institute for Molecules and Materials of Radboud University: ‘Making molecules is difficult enough. What is often harder, is to understand how certain molecules react, for example how they change when they are twisted or altered.’ How molecules change and react is the basis of chemistry, and leads to chemical reactions, like the formation of water from hydrogen and oxygen. ‘We wanted to simulate molecules, so we could have the ultimate toolkit to bend them and tune them in ways that are nearly impossible with real molecules. In that way we can say something about real molecules, without making them, or without having to deal with the challenges they present, like their constantly changing shape.’

Benzene

Using this simulator, the researchers created an artificial version of one of the basic organic molecules in chemistry: benzene. Benzene is the starting component for a vast amount of chemicals, like styrene, which is used to make polystyrene. Khajetoorians: ‘By making benzene, we simulated a textbook organic molecule, and built a molecule that is made up of elements that are not organic.’ Above that: the molecules are 10 times bigger than their real counterparts, which makes them easier to work with.

Practical uses

The uses of this new technique are endless. Daniel Wegner, assistant professor within the SPM department: ‘We have only begun to imagine what we can use this for. We have so many ideas that it is hard to decide where to start.’ By using the simulator, scientists can understand molecules and their reactions much better, which will help in every scientific field imaginable. Wegner: ‘New materials for future computer hardware are really hard to make, for instance. By making a simulated version, we can look for the novel properties and functionalities of certain molecules and evaluate whether it will be worth making the real material.’ In the far future, all kinds of things may be possible: understanding chemical reactions step by step like in a slow-motion video, or making artificial single-molecule electronic devices, like shrinking the size of a transistor on a computer chip. Quantum simulators are even suggested to perform as quantum computers. Sierda: ‘But that’s a long way to go, for now we can start by beginning to understand molecules in a way we never understood before.’

Researchers from UConn, the University of Florida, and the University of Pennsylvania tracked 153 weight loss program participants for six months where users self-reported their food intake using a commercial digital weight loss program. The researchers wanted to see what the optimal thresholds were for diet tracking to predict 3%, 5%, and 10% weight loss after six months.

“We partnered with WeightWatchers, who was planning on releasing a new Personal Points program, and they wanted to get empirical data via our clinical trial,” says co-author and Department of Allied Health Sciences Professor Sherry Pagoto.

Pagoto explains that the new program takes a personalized approach to assigning points including a list of zero-point foods to eliminate the need for calculating calories for everything,

“Dietary tracking is a cornerstone of all weight loss interventions, and it tends to be the biggest predictor of outcomes. This program lowers the burden of that task by allowing zero-point foods, which do not need to be tracked.”

Researchers and developers are seeking ways to make the tracking process less burdensome, because as Pagoto says, for a lot of programs, users may feel like they need to count calories for the rest of their lives: “That’s just not sustainable. Do users need to track everything every single day or not necessarily?”

With six months of data, Assistant Professor in the Department of Allied Health Sciences Ran Xu was interested to see if there was a way to predict outcomes based on how much diet tracking participants did. Ran Xu and Allied Health Sciences Ph.D. student Richard Bannor analyzed the data to see if there were patterns associated with weight loss success from a data science perspective. Using a method called receiver operating characteristics (ROC) curve analysis they found how many days people need to track their food to reach clinically significant weight loss.

“It turns out, you don’t need to track 100% each day to be successful,” says Xu. “Specifically in this trial, we find that people only need to track around 30% of the days to lose more than 3% weight and 40% of the days to lose more than 5% weight, or almost 70% of days to lose more than 10% weight. The key point here is that you don’t need to track every day to lose a clinically significant amount of weight.”

This is promising since Pagoto points out that the goal for a six-month weight loss program is typically 5% to 10%, a range where health benefits have been seen in clinical trials.

“A lot of times people feel like they need to lose 50 pounds to get healthier, but actually we start to see changes in things like blood pressure, lipids, cardiovascular disease risk, and diabetes risk when people lose about 5-to-10% of their weight,” says Pagoto. “That can be accomplished if participants lose about one to two pounds a week, which is considered a healthy pace of weight loss.”

Xu then looked at trajectories of diet tracking over the six months of the program.

The researchers found three distinct trajectories. One they call high trackers, or super users, who tracked food on most days of the week throughout six months, and on average lost around 10% of their weight.

However, many participants belonged to a second group that started tracking regularly, before their tracking gradually declined over time to, by the four-month mark, only about one day per week. They still lost about 5% of their weight.

A third group, called the low trackers, started tracking only three days a week, and dropped to zero by three months, where they stayed for the rest of the intervention. On average this group lost only 2% of their weight.

“One thing that is interesting about this data is, oftentimes in the literature, researchers just look at whether there is a correlation between tracking and overall weight loss outcomes. Ran took a data science approach to the data and found there is more to the story,” Pagoto says. “Now we’re seeing different patterns of tracking. This will help us identify when to provide extra assistance and who will need it the most.”

The patterns could help inform future programs which could be tailored to help improve user tracking based on which group they fall into. Future studies will dig deeper into these patterns to understand why they arise and hopefully develop interventions to improve outcomes.

“For me, what’s exciting about these digital programs is that we have a digital footprint of participant behavior,” says Xu. “We can drill down to the nitty-gritty of what people do during these programs. The data can inform precision medicine approaches, where we can take this data science perspective, identify patterns of behavior, and design a targeted approach.”

Digitally delivered health programs give researchers multitudes of data they never had before which can yield new insights, but this science requires a multidisciplinary approach.

“Before, it felt like we were flying in the dark or just going by anecdotes or self-reported measures, but it’s different now that we have so much user data. We need data science to make sense of all these data. This is where team science is so important because clinical and data scientists think about the problem from very different perspectives, but together, we can produce insights that neither of us could do on our own. This must be the future of this work,” says Pagoto.

Xu agrees: “From a data science perspective, machine learning is exciting but if we just have machine learning, we only know what people do, but we don’t know why or what to do with this information. That’s where we need clinical scientists like Sherry to make sense of these results. That’s why team science is so important.”

No longer flying in the dark, these multi-disciplinary teams of researchers now have the tools needed to start tailoring programs even further to help people achieve their desired outcomes. For now, users of these apps can be assured that they can still get significant results, even if they miss some entries.

The paper, which was published in Exercise and Sport Sciences Reviews, examines how a group of plant compounds that build up in the retina, known as macular pigments, work to improve eye health and functional vision.

Previous studies done by UGA researchers Billy R. Hammond and Lisa Renzi-Hammond have shown that eating foods like dark leafy greens or yellow and orange vegetables, which contain high levels of the plant compounds lutein and zeaxanthin, improves eye and brain health.

“A lot of the research into macular lutein and zeaxanthin has focused on health benefits, but from a functional perspective, higher concentrations of these plant pigments improve many aspects of visual and cognitive ability. In this paper, we discuss their ability to improve vision in the far distance or visual range,” said lead author Jack Harth, a doctoral candidate in UGA’s College of Public Health.

Visual range, or how well a person can see a target clearly over distance, is a critical asset for top athletes in almost any sport.

The reason why objects get harder to see and appear fuzzier the farther they are from our eyes is thanks in part to the effects of blue light.

“From a center fielder’s perspective, if that ball’s coming up in the air, it will be seen against a background of bright blue sky, or against a gray background if it’s a cloudy day. Either way, the target is obscured by atmospheric interference coming into that path of the light,” said Harth.

Many athletes already take measures to reduce the impact of blue light through eye black or blue blocker sunglasses, but eating more foods rich in lutein and zeaxanthin can improve the eye’s natural ability to handle blue light exposure, said Harth.

When a person absorbs lutein and zeaxanthin, the compounds collect as yellow pigments in the retina and act as a filter to prevent blue light from entering the eye.

Previous work had been done testing the visual range ability of pilots in the 1980s, and Hammond and Renzi-Hammond have done more recent studies on how macular pigment density, or how much yellow pigment is built up in the retina, is linked to a number of measures of eye health and functional vision tests.

“In a long series of studies, we have shown that increasing amounts of lutein and zeaxanthin in the retina and brain decrease glare disability and discomfort and improve chromatic contrast and visual-motor reaction time, and supplementing these compounds facilitates executive functions like problem-solving and memory. All of these tasks are particularly important for athletes,” said corresponding author Billy R. Hammond, a professor of psychology in the Behavior and Brain Sciences Program at UGA’s Franklin College of Arts and Sciences.

This paper, Harth said, brings the research on these links between macular pigment and functional vision up to date and asks what the evidence suggests about optimizing athletic performance.

“We’re at a point where we can say we’ve seen visual range differences in pilots that match the differences found in modeling, and now, we’ve also seen it in laboratory tests, and a future goal would be to actually bring people outside and to measure their ability to see contrast over distance through real blue haze and in outdoor environments,” said Harth.

But before you start chowing down on kale in the hopes of improving your game, he cautions that everybody is different. That could mean the way our bodies absorb and use lutein and zeaxanthin varies, and it could take a while before you notice any improvements, if at all.

Still, the evidence of the overall health benefits of consuming more lutein and zeaxanthin are reason enough to add more color to your diet, say the authors.

“We have data from modeling and empirical studies showing that higher macular pigment in your retina will improve your ability to see over distance. The application for athletes is clear,” said Harth.

Scientists have long considered another bacterial species, the plaque-forming, acid-making Streptococcus mutans, as the principal cause of tooth decay — also known as dental caries. However, in the study, which appeared 22 May in Nature Communications, the Penn Dental Medicine and UNC researchers showed that S. sputigena, previously associated only with gum disease, can work as a key partner of S. mutans, greatly enhancing its cavity-making power.

“This was an unexpected finding that gives us new insights into the development of caries, highlights potential future targets for cavity prevention, and reveals novel mechanisms of bacterial biofilm formation that may be relevant in other clinical contexts,” said study co-senior author Hyun (Michel) Koo DDS, PhD, a professor in the Department of Orthodontics and Divisions of Pediatrics and Community Oral Health and Co-Director of the Center for Innovation & Precision Dentistry at Penn Dental Medicine.

The other two co-senior authors of the study were Kimon Divaris, PhD, DDS, professor at UNC’s Adams School of Dentistry, and Di Wu, PhD, associate professor at the Adams School and at the UNC Gillings School of Global Public Health.

“This was a perfect example of collaborative science that couldn’t have been done without the complementary expertise of many groups and individual investigators and trainees,” Divaris said.

Caries is considered the most common chronic disease in children and adults in the U.S. and worldwide. It arises when S. mutans and other acid-making bacteria are insufficiently removed by teeth-brushing and other oral care methods, and end up forming a protective biofilm, or “plaque,” on teeth. Within plaque, these bacteria consume sugars from drinks or food, converting them to acids. If the plaque is left in place for too long, these acids start to erode the enamel of affected teeth, in time creating cavities.

Scientists in past studies of plaque bacterial contents have identified a variety of other species in addition to S. mutans. These include species of Selenomonas, an “anaerobic,” non oxygen-requiring group of bacteria that are more commonly found beneath the gum in cases of gum disease. But the new study is the first to identify a cavity-causing role for a specific Selenomonas species.

The UNC researchers took samples of plaque from the teeth of 300 children aged 3-5 years, half of whom had caries, and, with key assistance from Koo’s laboratory, analyzed the samples using an array of advanced tests. The tests included sequencing of bacterial gene activity in the samples, analyses of the biological pathways implied by this bacterial activity, and even direct microscopic imaging. The researchers then validated their findings on a further set of 116 plaque samples from 3 to 5-year-olds.

The data showed that although S. sputigena is only one of several caries-linked bacterial species in plaque besides S. mutans, and does not cause caries on its own, it has a striking ability to partner with S. mutans to boost the caries process.

S. mutans is known to use available sugar to build sticky constructions called glucans that are part of the protective plaque environment. The researchers observed that S. sputigena, which possesses small appendages allowing it to move across surfaces, can become trapped by these glucans. Once trapped, S. sputigena proliferates rapidly, using its own cells to make honeycomb-shaped “superstructures” that encapsulate and protect S. mutans. The result of this unexpected partnership, as the researchers showed using animal models, is a greatly increased and concentrated production of acid, which significantly worsens caries severity.

The findings, Koo said, show a more complex microbial interaction than was thought to occur, and provide a better understanding of how childhood cavities develop — an understanding that could lead to better ways of preventing cavities.

“Disrupting these protective S. sputigena superstructures using specific enzymes or more precise and effective methods of tooth-brushing could be one approach,” Koo said.

The researchers now plan to study in more detail how this anaerobic motile bacterium ends up in the aerobic environment of the tooth surface.

“This phenomenon in which a bacterium from one type of environment moves into a new environment and interacts with the bacteria living there, building these remarkable superstructures, should be of broad interest to microbiologists,” Koo said.

“Selenomonas sputigena acts as a pathobiont mediating spatial structure and biofilm virulence in early childhood caries” was co-authored by Hunyong Cho, Zhi Ren, Kimon Divaris, Jeffrey Roach, Bridget Lin, Chuwen Liu, M. Andrea Azcarate-Peril, Miguel Simancas-Pallares, Poojan Shrestha, Alena Orlenko, Jeannie Ginnis, Kari North, Andrea Ferreira Zandona, Apoena Aguiar Ribeiro, Di Wu and Hyun “Michel” Koo.

The work was funded in part by the National Institutes of Health (U01DE025046, R01DE025220, R03DE028983).