Now, an international and interdisciplinary team of researchers led by geneticists from Trinity College Dublin and zooarchaeologists from LMU Munich and the Bavarian State Collections of Natural History (SNSB) has deciphered the prehistoric cultural trajectory of this species by analysing 118 genomes recovered from archaeological bones dating across 12 millennia and stretching from Mongolia to Ireland.

The earliest sheep-herding village in the sample, Aşıklı Höyük in central Türkiye, has genomes that seem ancestral to later populations in the wider region, confirming an origin in captures of wild mouflon over 11,000 years ago in the western part of the northern Fertile Crescent.

By 8,000 years ago, in the earliest European sheep populations, the team found evidence that farmers were deliberately selecting their flocks — in particular for the genes coding for coat colour. Along with a similar signal in goats, this is the earliest evidence for human moulding of another animal’s biology and shows that early herders, like today’s farmers, were interested in the beautiful and unusual in their animals.

Specifically, the main gene the team found evidence of selection near was one known as “KIT,” which is associated with white coat colour in a range of livestock.

Also by that time, the earliest domestic sheep genomes from Europe and further east in Iran and Central Asia had diverged from each other. However, this separation did not last as people translocated sheep from eastern populations to the west.

First, in parallel with human cultural influences spreading out from the early cities of Mesopotamia we see sheep genomes moving west within the Fertile Crescent around 7,000 years ago.

Second, the rise of pastoralist peoples in the Eurasian steppes and their westward spread some 5,000 years ago profoundly transformed ancestral European human populations and their culture. This process changed the makeup of human populations, for example, altering the ancestry of British peoples by around 90%, and introduced the Indo-European language ancestor of the tongues spoken across the continent today.

From the dataset used in this study it now seems that this massive migration was fuelled by sheep herding and exploitation of lifetime products, including milk and probably cheese, as it is around the same time that sheep ancestries are also changed. Consequently, by the Bronze Age, herds had about half their ancestry from a source in the Eurasian steppe.

Dr Kevin Daly, Ad Astra Assistant Professor at UCD School of Agriculture and Food Science and an Adjunct Assistant Professor in Trinity’s School of Genetics and Microbiology, is the first author on the research article that has just been published in leading international journal Science. He said: “One of our most striking discoveries was a major prehistoric sheep migration from the Eurasian steppes into Europe during the Bronze Age. This parallels what we know about human migrations during the same period, suggesting that when people moved, they brought their flocks with them.”

Dan Bradley, leader of the research and Professor of Population Genetics in Trinity’s School of Genetics and Microbiology, said: “This research demonstrates how the relationship between humans and sheep has evolved over millennia. From the early days of domestication through to the development of wool as a crucial textile resource, sheep have played a vital role in human cultural and economic development.”

Joris Peters, co-corresponding author, Professor of Paleoanatomy, Domestication Research and the History of Veterinary Medicine at LMU Munich and Director of the State Collection for Paleoanatomy Munich (SNSB-SPM), said: “Our study, while convincingly reconciling morphological and genomic evidence of the geographic origin of domestic sheep, clearly illustrates that further transdisciplinary research is needed to clarify the patterns of dispersal and selection of the many landraces occurring today in Eurasia and Africa.”

“A recent global health report revealed that oral diseases — such as untreated tooth decay and gum disease — affected 3.5 billion people in 2022, making them the most widespread health conditions,” said study lead author Souvik Sen, M.D., M. S., M.P.H, chair of the Department of Neurology, Prisma Health Richland Hospital and the University of South Carolina School of Medicine in Columbia, South Carolina. “We aimed to determine which oral hygiene behavior — dental flossing, brushing or regular dentist visits — has the greatest impact on stroke prevention.”

The Atherosclerosis Risk in Communities (ARIC) study, one of the first large-scale investigations of this kind in the U.S., assessed the home use of dental floss through a structured questionnaire of more than 6,000 people. Among those who reported flossing, 4,092 had not experienced a stroke, and 4,050 had not been diagnosed with an irregular heartbeat known as atrial fibrillation (AFib).

Participants were asked about their status regarding high blood pressure, diabetes, high cholesterol, smoking, body mass index, education, regular brushing and dentist visits. During the 25 years of follow-up, 434 participants were identified as having strokes, of which 147 were larger artery brain clots, 97 were heart-driven clots and 95 were hardening of the smaller arteries. Additionally, 1,291 participants were noted to have experienced AFib.

The analysis found:

• Flossing was associated with a 22% lower risk of ischemic stroke, 44% lower risk of cardioembolic stroke (blood clots traveling from the heart) and 12% lower risk of AFib.
• The associated lower risk was independent of regular brushing and routine dental visits or other oral hygiene behaviors.
• Increasing the frequency of flossing had a greater chance of stroke risk reduction.
• Flossing was also associated with a lower chance of cavities and periodontal disease.

Researchers were surprised by the reduction of irregular heartbeats, or AFib. AFib is the most common form of irregular heartbeat. It can lead to stroke, heart failure or other cardiovascular complications. More than 12 million people are projected to have AFib in the United States by 2030, according to the American Heart Association’s 2025 Heart Disease and Stroke Statistics.

“Oral health behaviors are linked to inflammation and artery hardening. Flossing may reduce stroke risk by lowering oral infections and inflammation and encouraging other healthy habits,” Sen said. “Many people have expressed that dental care is costly. Flossing is a healthy habit that is easy to adopt, affordable and accessible everywhere.”

Study limitations include that data were based on answers to a questionnaire, and the 25-year follow-up appears to have focused on stroke and heart outcomes only. There was no follow-up concerning flossing or other oral behaviors over the years, Sen said.

“This study offers more insights into the specific dental health behaviors that may be linked to stroke risks and potential risk reduction. With further research, dental health practices could possibly be incorporated into the “Life’s Essential 8″ risk factors, which include diet, physical activity, nicotine exposure, sleep, body mass index, blood pressure, blood glucose and blood lipids,” said Daniel T. Lackland, Dr.P.H., FAHA, American Heart Association EPI and Stroke Council member and professor of epidemiology and director of the Division of Translational Neurosciences and Population Studies in the department of neurology at the Medical University of South Carolina in Charleston. Lackland was not involved in this study.

Study background, and details:

• The study began in 1987 and is ongoing.
• Of the 6,258 participants, 82% were self-reported white adults and 18% Black adults. Their average age was 62 years and 55% were women.
• Potential participants were excluded if they had total tooth loss, dental implants, heart disease, organ transplant, artificial joints, implanted heart valve or stent or major surgery.

“At first, these findings seemed to introduce a paradox: If scratching an itch is bad for us, why does it feel so good?” said senior author Daniel Kaplan, M.D., Ph.D., professor of dermatology and immunology at the University of Pittsburgh. “Scratching is often pleasurable, which suggests that, in order to have evolved, this behavior must provide some kind of benefit. Our study helps resolve this paradox by providing evidence that scratching also provides defense against bacterial skin infections.”

Allergic contact dermatitis is an allergic reaction to allergens or skin irritants — including poison ivy and certain metals such as nickel — leading to an itchy, swollen rash. Succumbing to the often-irresistible urge to scratch triggers further inflammation that worsens symptoms and slows healing.

To figure out what drives this vicious cycle, Kaplan, first author Andrew Liu, student in Pitt’s Medical Scientist Training Program, and their team used itch-inducing allergens to induce eczema-like symptoms on the ears of normal mice and those that don’t get itchy because they lack an itch-sensing neuron.

When normal mice were allowed to scratch, their ears became swollen and filled with inflammatory immune cells called neutrophils. In contrast, inflammation and swelling were much milder in normal mice that couldn’t scratch because they wore tiny Elizabethan collars, similar to a “cone of shame” that a dog might sport after a visit to the vet, and in animals that lacked the itch-sensing neuron. This experiment confirmed that scratching further aggravates the skin.

Next, the researchers showed that scratching causes pain-sensing neurons to release a compound called substance P. In turn, substance P activates mast cells, which are key coordinators of inflammation that drive itchiness and inflammation via recruitment of neutrophils.

“In contact dermatitis, mast cells are directly activated by allergens, which drives minor inflammation and itchiness,” explained Kaplan. “In response to scratching, the release of substance P activates mast cells through a second pathway, so the reason that scratching triggers more inflammation in the skin is because mast cells have been synergistically activated through two pathways.”

Mast cells are culprits in a range of inflammatory skin conditions and allergic reactions, but they’re also important for protecting against bacteria and other pathogens. As such, the researchers wondered if scratching-induced activation of mast cells could affect the skin microbiome.

In experiments led by coauthor Marlies Meisel, Ph.D., assistant professor of immunology at Pitt, the team showed that scratching reduced the amount of Staphylococcus aureus, the most common bacteria involved in skin infections, on the skin.

“The finding that scratching improves defense against Staphylococcus aureus suggests that it could be beneficial in some contexts,” said Kaplan. “But the damage that scratching does to the skin probably outweighs this benefit when itching is chronic.”

Now, the researchers are investigating new therapies for dermatitis and other inflammatory skin conditions such as rosacea and urticaria that suppress inflammation by targeting receptors on mast cells.

Other researchers on the study were Youran Zhang, Chien-Sin Chen, Ph.D., Tara N. Edwards, Ph.D., Torben Ramcke, M.D., Lindsay M. McKendrick, Eric S. Weiss, Jacob E. Gillis, Colin R. Laughlin, Simran K. Randhawa, Catherine M. Phelps, Kazuo Kurihara, M.D., Ph.D., Hannah M. Kang, Sydney-Lam N. Nguyen, Jiwon Kim, Tayler D. Sheahan, Ph.D., Sarah E. Ross, Ph.D., and Tina L. Sumpter, Ph.D., all of Pitt and UPMC; and Sumeyye Ozyaman, of Pitt and Istanbul Medipol University.

This research was supported by the National Institutes of Health (T32NS73548, T32CA0820840, R01DK130897, U24EY035102, K99NS126569, R01AR071720 and R01AR077341) and the German Research Foundation.

After some polar sleuthing, which involved scrutiny of hair collected from six polar bears in the wild, the scientists homed in on the hair “sebum” (or grease) as the all-important protectant. This sebum, which is made up of cholesterol, diacylglycerols, and fatty acids, makes it very hard for ice to attach to their fur.

While this finding sheds fascinating new light on our understanding of polar bear — and even Inuit — ecology, it may also have a suite of unrelated applications, with a similar concoction of artificially made sebum promising to be useful as an anti-ice surface coating, or in next-gen ski skins used by skiers and snowboarders.

Julian Carolan, PhD Candidate from Trinity College Dublin’s School of Chemistry and the AMBER Research Ireland Centre, is the first author of the journal article, which has been published today as the cover story in leading international journal Science Advances.

He said: “We measured ice adhesion strength, which is a useful measure of how well ice sticks to fur; hydrophobicity, which dictates whether water can be shed before it freezes; and freezing delay time, which simply shows how long it takes for a drop of water to freeze at certain temperatures on a given surface. We then compared the performance of the polar bear hair with that of human hair and two types of specialist human-made ‘ski skins’.

“The sebum quickly jumped out as being the key component giving this anti-icing effect as we discovered the adhesion strength was greatly impacted when the hair was washed. Unwashed, greasy hair made it much harder for ice to stick. In contrast when the polar bear hair was washed and the grease largely removed it performed similarly to human hair, to which ice sticks easily whether it is washed or greasy.”

That finding led the team to perform a detailed chemical analysis of polar bear sebum. As well as identifying the key components (cholesterol, diacylglycerols, and fatty acids), they were surprised to find “squalene” was absent. This fatty metabolite is present in human hair, and in the hair of other aquatic animals, like sea otters, which suggests its absence in polar bear hair is very important from an anti-icing perspective.

Dr Richard Hobbs, Assistant Professor and Royal Society-Science Foundation Ireland University Research Fellow in Trinity’s School of Chemistry and the AMBER Research Ireland Centre, is a senior author of the journal article. He added: “Animals living in polar habitats have emerged as a source of inspiration for the development of new anti-icing materials.

“For example, Anne Kietzig’s group at McGill recently found that the hierarchical structure of Gentoo penguin feathers afforded them anti-icing properties that relied on the feather structure rather than the preen oil coating. Our work shows that polar bear fur provides an alternative strategy to produce an anti-icing surface based on the characteristic blend of lipids present in their fur sebum or hair grease.

“This work not only represents the first study of the composition of polar bear fur sebum, but it also resolves the question of why polar bears don’t suffer from ice accumulation. Despite having thick layers of insulating blubber and fur, and spending extensive periods in water at sub-zero temperatures, it seems that the fur grease provides a natural route for polar bears to easily shed ice when it forms due to the low ice adhesion on their fur.

“We expect that these natural lipid coatings produced by the bear will help us to develop new more sustainable anti-icing coatings that may replace problematic ‘forever chemicals’ like PFAS that have been used as anti-icing coatings.”

In addition to the structural explanations, these interesting discoveries also help us better understand hunting behaviours — both of polar bears and of native Inuit populations.

Prof. Bodil Holst, University of Bergen, is a senior author of the journal article. She added: “One of the polar bears’ main hunting strategies is ‘still hunting’, where they lay motionless beside a breathing hole on sea ice waiting for seals to surface. Still hunting frequently develops into an ‘aquatic stalk’ with the polar bear using its hind paws to slide into the water to pursue its prey, and the lower the ice adhesion, the less noise generated and the faster and quieter the slide.

“Our findings also help us understand the subtlety of the steps taken by Inuit people to optimise hunting strategies to mimic the polar bear method of still hunting. Inuit hunting stools are sometimes shod with polar bear fur on the feet to avoid noise when moving on the ice, while people also sometimes wear ‘polar bear trousers’, ensuring the entire contact area with the ice is covered in low ice-adhesion polar bear fur for optimal noise reduction.”

Notably, the traditional Inuit preparation method protects the sebum on the fur by ensuring the hair-covered side of the skin is not washed. This is unlike, for example, a fox skin, which would traditionally be cleaned by rubbing the hair side with soapstone or dry clay.

A team of researchers led by Celia Romero, a graduate student in clinical psychology, along with associate professor Lynn Perry, professor Michael Alessandri, and former University professor Lucina Uddin, explored the role of bilingualism in 112 children, including typically developing children and children with autism, between the ages of 7 to 12 years old. Overall, they found that children who spoke two or more languages often had stronger executive functioning skills. This means they are able to control impulses and to switch between different tasks more easily than children who only spoke one language.

“We discovered that multilingualism is associated with improvements in executive function, which in turn is associated with improvements in autism symptoms,” Perry said. “There were hints of this in the literature before, but it was exciting to see how far reaching those differences were in this research.”

Published in the journal Autism Research, the results are significant because executive functioning skills are a key challenge for children on the spectrum but are important for all kids to thrive in school and later in the workplace. Yet, the team found the benefits of speaking more than one language were not limited to children with autism.

Key features of autism include social communication difficulties and restrictive and repetitive behaviors, as well as difficulty with executive function skills. These are mental processes that help us plan, focus, remember instructions, and manage multiple tasks effectively. While executive function skills develop and improve across the lifespan, individuals with autism often struggle with executive functioning, impacting their ability to manage daily tasks and adapt to new situations.

The study also looked at the impact of multilingualism on core symptoms of autism, including perspective taking, restricted and repetitive behaviors, and social communication.

“We also found that multilingual children have enhanced perspective taking skills, or the ability to understand someone else’s thoughts or point of view,” Romero added.

An idea called joint activation from the field of neuroscience can help explain the results. Prior research suggests that the bilingual brain has two languages constantly active and competing. As a result, the daily experience of shifting between these languages is associated with enhanced executive control. This concept is also known as the “bilingual advantage” and is a topic of much debate.

“If you have to juggle two languages, you have to suppress one in order to use the other. That’s the idea, that inhibition — or the ability to stop yourself from doing something — might be bolstered by knowing two languages,” said Uddin, now a professor at the University of California, Los Angeles, and director of the Brain Connectivity and Cognition Laboratory.

Romero realized she wanted to explore this topic while working in Uddin’s neuroscience lab on campus that was doing brain imaging research on children with autism. She noticed that some bilingual families did not speak to their child in their native language because they thought it may be too challenging and harmful for their child to learn more than one language.

“I started investigating this to let families know there’s no detriment for their child to learn another language, whether or not they have a neurodevelopmental disorder,” she said. “We know this through research, but often it takes time to translate that to families, so I hope this study helps address that.”

In his work as executive director of the University’s Center for Autism and Related Disabilities, Alessandri said this question often comes up with parents.

“It is wonderful to have sound research supporting our general recommendation to not restrict language exposures to children in multilingual homes,” Alessandri said. “This will surely bring a sense of relief to many of our families living with loved ones with autism.”

Romero and Perry are now doing further research with preschool children to see if bilingualism also has an impact on kids’ peer interactions, which are crucial for children’s social and cognitive development. And at UCLA, Uddin is currently conducting a large follow-up study to further investigate the impact of multilingualism on brain and cognitive development in children with autism.

Now, new research led by Joshua Kim and Mathew Madhavacheril at the University of Pennsylvania and their collaborators at Lawrence Berkeley National Laboratory suggests our universe has become “messier and more complicated” over the roughly 13.8 billion years it’s been around, or rather, the distribution of matter over the years is less “clumpy” than expected.

“Our work cross-correlated two types of datasets from complementary, but very distinct, surveys,” says Madhavacheril, “and what we found was that for the most part, the story of structure formation is remarkably consistent with the predictions from Einstein’s gravity. We did see a hint for a small discrepancy in the amount of expected clumpiness in recent epochs, around four billion years ago, which could be interesting to pursue.”

The data, published in the Journal of Cosmology and Astroparticle Physics and the preprint server arXiv, comes from the Atacama Cosmology Telescope’s (ACT) final data release (DR6) and the Dark Energy Spectroscopic Instrument’s (DESI) Year 1. Madhavacheril says that pairing this data allowed the team to layer cosmic time in a way that resembles stacking transparencies of ancient cosmic photographs over recent ones, giving a multidimensional perspective of the cosmos.

“ACT, covering approximately 23% of the sky, paints a picture of the universe’s infancy by using a distant, faint light that’s been travelling since the Big Bang,” says first author of the paper Joshua Kim, a graduate researcher in the Madhavacheril Group. “Formally, this light is called the Cosmic Microwave Background (CMB), but we sometimes just call it the universe’s baby picture because it’s a snapshot of when it was around 380,000 years old.”

The path of this ancient light throughout evolutionary time, or as the universe has aged, has not been a straight one, Kim explains. Gravitational forces from large, dense, heavy structures like galaxy clusters in the cosmos have been warping the CMB, sort of like how an image is distorted as it travels through a pair of spectacles. This “gravitational lensing effect,” which was first predicted by Einstein more than 100 years ago, is how cosmologists make inferences about its properties like matter distribution and age.

DESI’s data, on the other hand, provides a more recent record of the cosmos. Based in the Kitt Peak National Observatory in Arizona and operated by the Lawrence Berkeley National Laboratory, DESI is mapping the universe’s three-dimensional structure by studying the distribution of millions of galaxies, particularly luminous red galaxies (LRGs). These galaxies act as cosmic landmarks, making it possible for scientists to trace how matter has spread out over billions of years.

“The LRGs from DESI are like a more recent picture of the universe, showing us how galaxies are distributed at varying distances,” Kim says, likening the data to the universe’s high school yearbook photo. “It’s a powerful way to see how structures have evolved from the CMB map to where galaxies stand today.

By combining the lensing maps from ACT’s CMB data with DESI’s LRGs, the team created an unprecedented overlap between ancient and recent cosmic history, enabling them to compare early- and late-universe measurements directly. “This process is like a cosmic CT scan,” says Madhavacheril, “where we can look through different slices of cosmic history and track how matter clumped together at different epochs. It gives us a direct look into how the gravitational influence of matter changed over billions of years.”

In doing so they noticed a small discrepancy: the clumpiness, or density fluctuations, expected at later epochs didn’t quite match predictions. Sigma 8 (σ8), a metric that measures the amplitude of matter density fluctuations, is a key factor, Kim says, and lower values of σ8 indicate less clumping than expected, which could mean that cosmic structures haven’t evolved according to the predictions from early-universe models and suggest that the universe’s structural growth may have slowed in ways current models don’t fully explain.

This slight disagreement with expectations, he explains, “isn’t strong enough to suggest new physics conclusively — it’s still possible that this deviation is purely by chance.”

If indeed the deviation is not by chance, some unaccounted-for physics could be at play, moderating how structures form and evolve over cosmic time. One hypothesis is that dark energy — the mysterious force thought to drive the universe’s accelerating expansion — could be influencing cosmic structure formation more than previously understood.

Moving forward, the team will work with more powerful telescopes, like the upcoming Simons Observatory, which will refine these measurements with higher precision, enabling a clearer view of cosmic structures.