One of the method’s applications is to give a more complete sense of human ancestry, says Gideon Bradburd, U-M professor of ecology and evolutionary biology. For example, when you send your DNA off for a personalized ancestry report, the report you get back is only a very small view of your family tree pinned in a specific point and space in time.

These types of genetic reports reflect the amount of a person’s genome that they’ve inherited from individuals living in a specific area at a specific point in the past. If your ancestry report says that you’re 50% Irish, that means you have a lot of second through fourth cousins who currently live in Ireland, says Bradburd. But in reality, your family tree is much more like a movie than this snapshot.

The statistical method developed by Bradburd and fellow U-M researchers Michael Grundler and Jonathan Terhorst can give people a “movie” version of their ancestry, showing where their ancestors originated and how they moved across the globe. The method uses modern genetic sequence samples, estimates all of the locations of an individual’s genetic ancestors, identifies the average location of those individuals based on assumptions about how people move, and tracks it back over centuries.

The researchers’ method can be used for more than tracing human ancestry. It can also be used to track the emergence of viruses, the divergence of animal populations and other genealogical tracking. Their results are published in the journal Science.

“There’s ways in which consumer ancestry reports are interesting, and certainly it’s powerful to learn about your history, especially for folks who’ve been adopted or orphaned or are disconnected from their family,” Bradburd said. “But there are other ways in which these ancestry reports can be really problematic. They really reify notions of the biological essentialism of race because they’re presenting these categories of Irish, for example, as if they’re ideals, that they’re real and unchanging through time.”

But researchers know this isn’t the case. A field, forged by Nobel Prize-winning geneticist Svante Pääbo, developed the tools to genotype ancient DNA. This allows researchers to trace waves of human populations as they spread throughout the world — particularly in Eurasia, where most of this type of genetic sequencing has been happening, Bradburd says. This has allowed researchers to see how human groups enter and leave geographic regions through time.

“Because the genetic flavor of a location changes so much through time, we know it’s meaningless to say, ‘This is what it means to be Irish,'” Bradburd said. “It’s not just that being ‘genetically Irish’ doesn’t mean anything; it also means that you are everything.”

Bradburd points to a thought experiment in human biology: imagine two biological parents and four biological grandparents. This doubles every generation, and it only has to double a relatively small number of generations before there are more people in that direct lineage than there have ever been humans alive on Earth.

This also means that you don’t have to go very far back in time to discover that many people share many ancestors.

“Because our pedigrees explode so quickly, they also must collapse in the same sense that you and I must share many, many relatives at many points back in time, and that’s true for every person alive on Earth,” Bradburd said. “We’re all extraordinarily closely related to each other.”

The ancestry reports are accurate, Bradburd said, but specifically when they are tied to a time period.

“The ancestry reports aren’t wrong, but they’re leaving out a very important component, which is the ‘when’ you have Irish ancestry,” Bradburd said. “Because we know the modern human lineage arose in Africa, it is as accurate to say that you have 100% African ancestry at a deeper time horizon.”

The statistical method, called Gaia (geographic ancestry inference algorithm), starts by making a very simple assumption about how individuals move: that typically they move locally. The method combines that assumption with the location of modern-day individuals and a genetic structure that relates them called the ancestral recombination graph.

With those two pieces of information and the simple model of how individuals move, the researchers can compute the “most parsimonious locations of ancestors,” Bradburd says. The researchers then can propagate that information back through the past.

Bradburd’s work is answering a call from the National Academy of Sciences, urging researchers working on human population genetics to move away from race-based labels. While the sociological realities of race are undeniable, racial categories do not make good predictions about genetic variation, he says.

Because of the disconnect between race and genetics, racial labels can often be imprecise: two people might share the same label, but be much more closely or less closely related to each other. In addition, because the genetics in a certain geographic area can shift so much over time, geographic and national labels can also be misleading, Bradburd says.

“Saying you’re ‘genetically Irish’ makes it seem like ‘Irish’ has always meant the same thing, and genetically we know that is not true and also that anyone who is Irish — meaning they inherited parts of their genome from people who lived in Ireland — is only Irish with respect to a specific time horizon,” he said. “That these race labels gloss over both of these important pieces of information is a big loss of specificity and also poses a very real danger to the weaponization of science for political means.”

The method Bradburd’s team developed can be applied to systems other than human genetics. Researchers can use this method to look at the genetic distribution of the organisms they study. Researchers can also use this method to learn about the migration of organisms — human and otherwise, Bradburd says.

For example, researchers have been able to look at measures of genetic similarity of population between two locations and infer that they are more or less closely connected by migration, or more or less isolated from each other. But this tool allows researchers to pin a timeline on when these movements happened.

And this tool can apply in this case to more than tracing human genetics — it can be used to help determine when a disease might have emerged from a specific region of the world, for example. The U-M group is working with researchers in Australia to learn how mosquitoes colonized islands of the South Pacific, and with researchers in Michigan and Ohio to understand the history and dispersal of the Massasauga rattlesnake.

“It’s one of the things I’m quite excited about with this — you can use this method to identify dispersal patterns through time and between specific locations,” Bradburd said. “Notions of ancestry don’t have to be static. Instead, you should think of them as being dynamic, and interesting and understandable more as a movie than as a picture.”

The discrepancy between model results and observed cooling, Stanford University scientists have now found, comes down mainly to missing meltwater and underestimated rainfall.

“We found that the Southern Ocean cooling trend is actually a response to global warming, which accelerates ice sheet melting and local precipitation,” said Earle Wilson, an assistant professor of Earth system science in the Stanford Doerr School of Sustainability and senior author of the March 27 study in Geophysical Research Letters.

As rising temperatures melt Antarctica’s ice sheet and cause more precipitation, the Southern Ocean’s upper layer is growing less salty — and thus, less dense. This creates a lid that limits the exchange of cool surface waters with warmer waters below. “The fresher you make that surface layer, the harder it is to mix warm water up,” Wilson explained.

But this freshening is not fully represented in state-of-the-art climate models — a flaw that scientists have long recognized as a major source of uncertainty in projections of future sea level rise. “The impact of glacial meltwater on ocean circulation is completely missing from most climate models,” Wilson said.

Reconciling global discrepancies

The mismatch between observed and simulated sea surface temperatures around Antarctica is part of a larger challenge for scientists and governments seeking to prepare for climate impacts. Global climate models generally do not accurately simulate the cooling observed over the past 40 years in the Southern Ocean and the eastern Pacific around the equator or the intensity of the warming observed in the Indian and western Pacific Oceans. There is also a discrepancy between simulations and the observed frequency of La Niña weather conditions, defined by the eastern Pacific being colder than average.

Warming events in the Southern Ocean over roughly the past eight years have somewhat diminished the 40-year-long cooling trend. But if sea surface temperature trends around the globe continue to resemble patterns that have emerged in recent decades, rather than shifting toward the patterns predicted in simulations, it would change scientists’ expectations for some near-term impacts from climate change. “Our results may help reconcile these global discrepancies,” Wilson said.

Oceans globally have absorbed more than a quarter of the carbon dioxide emitted by human activities and more than 90% of the excess heat trapped in our climate system by greenhouse gases. “The Southern Ocean is one of the primary places that happens,” said lead study author Zachary Kaufman, a postdoctoral scholar in Earth system science.

As a result, the Southern Ocean has an outsized influence on global sea level rise, ocean heat uptake, and carbon sequestration. Its surface temperatures affect El Niño and La Niña weather patterns, which influence rainfall as far away as California.

A surprising discovery

To understand the physical mechanism for Southern Ocean cooling — and enable more reliable projections of its future impacts on Earth’s climate system — Wilson and Kaufman set out to determine how much sea surface temperatures around Antarctica in simulations have cooled in response to freshening. “We naively figured it wouldn’t matter exactly where you put the freshwater,” Wilson said.

The researchers were surprised to discover that surface temperatures are much more sensitive to freshwater fluxes concentrated along the coast than those splashing more broadly across the ocean as rain.

“Applying freshwater near the Antarctic margin has a bigger influence on sea ice formation and the seasonal cycle of sea ice extent, which then has downstream impacts on sea surface temperature,” Wilson said. “This was a surprising result that we are eager to explore further in future work.”

Quantifying the effect of missing meltwater

Previous studies have sought to quantify how Antarctic meltwater affects the global climate system by adding some amount of freshwater to a single climate model simulation, in what scientists have dubbed “hosing” experiments. “You get very divergent results, because people set up their experiments slightly differently, and the models are a little different, and it’s unclear if these are really apples-to-apples comparisons,” Wilson explained.

For the new study, the researchers sought to avoid this issue by working with a collection of simulations. Using a new ensemble of coupled climate and ocean models from the recently launched Southern Ocean Freshwater Input from Antarctica (SOFIA) Initiative, as well as an older set of models simulating ocean density and circulation changes, the authors analyzed how much simulated sea surface temperatures changed in response to the actual freshwater inputs between 1990 and 2021.

“There’s been some debate over whether that meltwater is enough over the historical period to really matter,” said Kaufman. “We show that it does.”

With the new method, which incorporates simulations from 17 different climate models, the researchers found missing freshwater explains up to 60% of the mismatch in observed and predicted Southern Ocean surface temperatures between 1990 and 2021.

“We’ve known for some time that ice sheet melting will impact ocean circulation over the next century and beyond,” Wilson said. “Our results provide new evidence that these meltwater trends are already altering ocean dynamics and possibly the global climate.”

Additional co-authors include Yuchen Li, an undergraduate student in the Physics Department in the Stanford School of Humanities and Sciences, Ariaan Purich of Monash University, and Rebecca Beadling of Temple University.

This research was supported by Stanford University, a grant from the NSF Division of Polar Programs, and the Australian Research Council Special Research Initiative for Securing Antarctica’s Environmental Future. Li was supported by the Sustainability, Engineering and Science — Undergraduate Research (SESUR) program in the Stanford Doerr School of Sustainability.

The study, which was published in the Journal of Health Psychology, looked at how patients with Long Covid experience their illness. The study found that many patients feel they have to prove their illness is physical to be taken seriously and, as a result, often reject psychological support, fearing it implies their symptoms are “all in the mind.”

Professor Jane Ogden, co-author of the study from the University of Surrey, said:

“We found that the problem isn’t people with Long Covid refusing help — it’s about the deep need for people to be believed. When a patient feels dismissed, offering psychological support instead of medical care can be misconstrued as insulting.”

According to the Office for National Statistics, there are 1.9 million people who live with Long Covid in the UK. Long Covid symptoms include fatigue, difficulty concentrating, muscle aches and shortness of breath, which persist for many weeks, sometimes months, after the initial Covid-19 infection.

Surrey’s study involved in-depth interviews with 14 people in the UK between the ages of 27 to 63 who had experienced Long Covid symptoms for more than four weeks. The group included 12 women and two men.

Saara Petker, clinical psychologist, co-author of the study and former PhD student at the University of Surrey, said:

“We found that our participants are living a life of constant uncertainty, struggling to find treatment. People told us that they didn’t feel listened to, some said they’d lost trust in doctors, their social circles and even their own bodies because of the whole experience.

“Medical advice is crucial — but psychological support must be offered with care. If it’s seen as replacing medical help, it can feel dismissive.”

“This study is the first to demonstrate, using a physical model, that the first-order features of Earth’s lower mantle structure were established four billion years ago, very soon after the planet came into existence,” says lead author Faculty of Science Assistant Professor Charles-Édouard Boukaré in the Department of Physics and Astronomy at York.

The mantle is the rocky envelopment that surrounds the iron core of rocky planets. The structure and dynamics of the Earth’s lower mantle play a major role throughout Earth’s history as it dictates, among others, the cooling of the Earth’s core where the Earth’s magnetic field is generated.

Boukaré originally from France, worked with research colleagues from Paris on the paper, Solidification of Earth’s mantle led inevitably to a basal magma ocean, published today in Nature.

Boukaré says that while seismology, geodynamics, and petrology have helped answer many questions about the present-day thermochemical structure of Earth’s interior, a key question remained: how old are these structures, and how did they form? Trying to answer this, he says, is much like looking at a person in the form of an adult versus a child and understanding how the energetic conditions will not be the same.

“If you take kids, sometimes they do crazy things because they have a lot of energy, like planets when they are young. When we get older, we don’t do as many crazy things, because our activity or level of energy decreases. So, the dynamic is really different, but there are some things that we do when we are really young that might affect our entire life,” he says “It’s the same thing for planets. There are some aspects of the very early evolution of planets that we can actually see in their structure today.”

To better understand old planets, we must first learn how young planets behave.

Since simulations of the Earth’s mantle focus mostly on present-day solid-state conditions, Boukaré had to develop a novel model to explore the early days of Earth when the mantle was much hotter and substantially molten, work that he has been doing since his PhD.

Boukaré’s model is based on a multiphase flow approach that allows for capturing the dynamics of magma solidification at a planetary scale. Using his model, he studied how the early mantle transitioned from a molten to a solid state. Boukaré and his team were surprised to discover that most of the crystals formed at low pressure, which he says creates a very different chemical signature than what would be produced at depth in a high-pressure environment. This challenges the prevailing assumptions in planetary sciences in how rocky planets solidify.

“Until now, we assumed the geochemistry of the lower mantle was probably governed by high-pressure chemical reactions, and now it seems that we need to account also for their low-pressure counterparts.”

Boukare says this work could also help predict the behaviour of other planets down the line.

“If we know some kind of starting conditions, and we know the main processes of planetary evolution, we can predict how planets will evolve.”

A U.S. Department of Energy-funded study, “Deconstruction of Rubber via C-H Amination and Aza-Cope Rearrangement,” recently published in Nature and led by Dr. Aleksandr Zhukhovitskiy, William R. Kenan, Jr. Fellow and Assistant Professor in the Department of Chemistry at UNC-Chapel Hill, introduces a novel chemical method for breaking down rubber waste. This pioneering technique utilizes C-H amination and a polymer rearrangement strategy to transform discarded rubber into valuable precursors for epoxy resins, offering an innovative and sustainable alternative to traditional recycling methods.

Rubber, including the synthetic kind used in tires, is composed of polymers cross-linked together into a three-dimensional network that behaves as a tough, flexible material. Recycling these materials is difficult due to the extensive cross-linking within the polymer structure, which gives rubber its durability but also makes it resistant to degradation. Traditional methods for breaking down rubber focus on two main approaches: de-vulcanization, which breaks sulfur cross-links but weakens the polymer’s mechanical properties, and cleavage of the polymer backbones using oxidative or catalytic methods, which often result in complex, low-value byproducts. Neither approach provides an efficient, scalable solution for repurposing rubber waste.

“Our research seeks to overcome these challenges by developing a method that breaks down rubber into functional materials that possess value even as a mixture,” said Dr. Zhukhovitskiy, who is the corresponding author of the study.

The researchers introduce a sulfur diimide reagent that enables the installation of amine groups at specific locations in the polymer chains. This step is crucial because it sets the stage for the subsequent backbone rearrangement. This chemical reaction reorganizes the polymer backbone, breaking down the rubber into soluble amine-functionalized materials that can be used to produce epoxy resins.

The researchers showed that their two-step process works very well. In a test with a model polymer, they broke it down significantly, reducing its molecular weight from 58,100 g/mol to about 400 g/mol. When they applied the method to used rubber, it broke down completely in just six hours, turning it into a soluble material with amine groups that could be used to manufacture broadly useful materials like epoxy resins.

The efficiency of this method is particularly striking when compared to traditional recycling techniques, which often require extreme temperatures or expensive catalysts. The researchers achieved their results under mild conditions (35-50°C, or 95-122°F) in aqueous media, making the process more environmentally friendly and cost-effective.

Epoxy resins are widely used in industries for adhesives, coatings, and composites. They are usually made from petroleum-based chemicals like bisphenol A and curing agents. This research shows that amine-modified poly-dienes, produced using the researchers’ method, can create epoxy materials with strength similar to commercial resins.

“In moments like this I come to appreciate the power of organic synthesis,” said Maxim Ratushnyy, a co-author of the paper and former postdoctoral scholar at UNC-Chapel Hill. “It is fascinating to see the ease with which the developed sequence of simple, yet powerful, organic transformations can take on a stubborn C — C bond and convert polybutadiene and polyisoprene-based rubbers into potentially valuable epoxy resins.”

Beyond its practical applications, this study marks a significant step toward greener recycling technologies. The researchers evaluated the environmental impact of their process using the Environmental Impact Factor (E-factor), a measure of waste generated relative to the product yield.

“E-factor is a simple but powerful metric to compare the impact of a new process to incumbents, but also to highlight process steps that can be improved as we work to transition this process out of the lab and into practice,” said Dr. Geoff Lewis, a research specialist at the University of Michigan’s Center for Sustainable Systems.

While the complete E-factor, which includes solvent use, was high, the simple E-factor, excluding solvents, was much lower, highlighting areas where the process could be further optimized for sustainability. The team is already exploring greener solvent systems and alternative reaction conditions to reduce waste generation.

“Our research represents a paradigm shift in how we approach the problem of rubber waste,” said Sydney Towell, a co-author of the study and Ph.D. candidate at UNC-Chapel Hill. “By harnessing the power of C-H amination and backbone rearrangement, this method provides a new pathway to transforming post-consumer rubber into high-value materials, reducing reliance on landfills and minimizing environmental harm.”

Obesity is considered to be a global public health concern, but experts still disagree about the precise origins and causes of rising obesity rates. One topic under debate is whether a person’s individual genetics and behaviors are more or less important than environmental factors, like socioeconomic status, in developing obesity.

In the new study, researchers estimated the impact of several factors on a person’s weight, including societal factors, like a person’s job type, as well as early life factors, like a person’s birth order, how they were delivered and whether their mother smoked or was obese. They looked specifically at whether a person was overweight, obese or severely obese at age 16 and age 42. They also looked at participants’ weight between ages 16 to 42, a range that spans the rise in obesity rates in the United Kingdom. The data came from the 1958 National Child Development Study, a long-term study that followed the lives of more than 17,000 people born in a single week in March 1958 across England, Scotland and Wales.

The analysis showed that if a mother was obese or if she smoked, her child was more likely to be obese or severely obese at each of the ages examined. The findings demonstrate that these early life factors can have a persistent effect on a person’s weight. Notably, these factors were just as powerful before and after the start of the rise in obesity rates in the UK, suggesting that the impact of individual factors, like behaviors, likely did not change during that time.

The results suggest that societal and early-life risk factors could be used to target obesity prevention programs for children and adults. The researchers also conclude that, since individual risk factors have not changed as obesity rates have risen, new studies are needed to identify societal factors that may have caused the current obesity pandemic.

The authors add: “Our research shows that the effect of maternal influences persists through to age 42 and that strikingly, those predictors were just as powerful (and prevalent) in the era before the current obesity pandemic began. This suggests that, as Geoffrey Rose pointed out, novel studies are needed of factors at the community/societal level that may have caused the current obesity pandemic, since individual-level risk factors appear not to have changed over the time period spanning the pandemic’s onset and growth.”