The jaws of some sea worms are made of an exceptionally hard yet lightweight material dubbed a “bio-metal” that could have applications in engineering.

Perinereis cultrifera is a type of ragworm with a long body adorned with bristles. Members of the species also have strong jaws that enable them to crush hard prey such as small crustaceans or other worms. Remnants of their jaws have been found in the fossil record dating back to hundreds of millions of years ago.

at TU Wien in Austria and his colleagues have been studying this worm’s jaws for almost a decade, leading them to propose that they are made of a novel material. The molecular structure of each jaw combines proteins and ions of metals such as zinc, giving it characteristics in between those of softer biological materials and metals.

Most recently, the team performed more than 3300 experiments in which small indentations were made in different parts of the jaw. The way its hardness changed under this pressure followed a pattern typical of metals like copper and silver. But the jaw also exhibited a kind of elasticity that metals cannot have, says Hellmich.

Finally, the researchers developed a mathematical model of bio-metals, which shows how they might respond to strain in a unique way in which microscopic forces arise from the metal ions becoming arranged into lines similar to certain defects in crystals.

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The researchers were surprised to uncover so much novelty in the relatively simple animal. Performing mechanical tests on the millimetre-sized jaw was really challenging and required hundreds of hours of preparation and polishing, says Hellmich. “Basically, anything can go wrong,” he says.

“The jaws of bristle worms are incredibly hard yet very lightweight,” says at Kent State University in Ohio. “Many industries, from automobiles to aeronautics, are searching for new ways to develop hard and lightweight materials. The answers are provided in nature!”

“Somehow evolution figured out a way to coax a metal-like mechanical fingerprint out of protein-like ingredients, and studying the worm is how we ask what trick makes that possible,” says at the Massachusetts Institute of Technology, who didn’t work on the study. The long-term dream outcome of this research is to genetically program materials that would grow in biological systems, he says.

Hellmich and his colleagues are interested in pursuing this goal and their team already includes geneticists and biologists at the University of Vienna. “We are asking questions like, ‘If we knock out a few genes, then how will the jaws be different?’” he says.

An ancient Maya astronomer-mathematician has been identified for the first time along with his complex calculations made around 1200 years ago, predicting the orbital cycles of Mars and Venus.

“This is the first direct mention of an ancestral Maya astronomer-mathematician by personal name,” says at the Massachusetts Institute of Technology.

It is also the oldest recorded name of an astronomer-mathematician ever known from anywhere in the Americas, he says.

The Maya civilisation flourished in Central America between roughly 2000 BC and AD 1697. They had advanced knowledge of mathematics and astronomy, but much of it was lost after the mass burning of their books by Spanish missionaries.

Since 2010, excavations at the site of Xultun, Guatemala, have revealed astronomical and mathematical inscriptions inside a small masonry building.

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On the east and north-east wall of the building are around 50 texts that scientists believe are “rough drafts” made by Maya mathematicians as they charted and predicted the cycles of celestial objects relative to Earth and to one another.

Rossi and his colleagues have painstakingly deciphered one of these murals, named Text 19. At the bottom of the mural is the name of Sak Tahn Waax, which translates to White-chested Fox, who is believed the be the author of the formula.

Text 19 consists of 11 hieroglyphs, which had to be scanned, photographed and magnified under different illumination angles, and compared to other, later, astronomical-mathematical writings, before their meaning could be deduced.

While similar mathematical and astronomical expertise is found across Maya cities, the mention of Sak Tahn Waax, who the researchers believe was probably male, is unique.

“Whether this is an instance of the scribe himself signing his own calculation or attributing the intellectual work to another, we have a formula and the name of its creator, which serves to demonstrate the importance of this kind of intellectual contribution for Classic Maya people,” says Rossi.

The calendar system on display in Text 19 uses maths in relation to time periods, he says. These time periods were drawn from a 260-day calendar, a 365-day solar calendar, a 584-day approximation of Venus’s synodic cycle (when the planet returns to the same position relative to both Earth and the sun) and a 780-day approximation of Mars’s synodic cycle. The total length of the formula is five Venus synodic cycles or 2920 days, and the date that Text 19 most likely refers to is 7 November of AD 781 in the Julian calendar.

Exactly how this formula would have been applied is unknown, says Rossi, as it “isn’t incorporated into any larger body of work”.

“We think it is meant to concisely and meaningfully show the relationship between these two planets and human counts of time in ways that could then be applied to political ceremony, predictive astronomy and understandings of seasonality,” he says.

Such meticulous mathematical legwork would have been critical to structuring life in a world before computers, smartphones and weather apps, says Rossi.

A cognitive “speed training” game that cuts dementia risk by 25 per cent alters levels of beta-amyloid, a protein that clogs up the brain in Alzheimer’s disease, in men, but not in women.

It is the first time brain training has been shown to influence the levels of a neurodegenerative marker, strengthening the evidence suggesting that mental exercises can boost brain health.

“One of the main markers that’s indicative of future dementia risk got better for men who completed cognitive speed training,” says  at Clemson University in South Carolina, who presented the research at the Alzheimer’s Association International Conference in London on 12 July.

The computer-based speed training involves recalling where objects have flashed up, with the task becoming harder as performance improves. A prior 20-year study by some of Chai’s colleagues showed that people aged 65 and older, who did the training were 25 per cent less likely to be diagnosed with Alzheimer’s disease or a related form of dementia compared with a control group.

In the latest study, Chai and her team recruited a separate group of 53 people from the US aged 65 and older, 13 of whom were male. About a third of the participants were asked to complete between 2 and 4 hours of speed training each week for 4.5 months.

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The remaining participants were either told to spend the same amount of time playing games such as Solitaire, word search and a game similar to Connect 4, or to complete another kind of brain training in which they had to strategically track objects and switch between tasks.

To explore how speed training may reduce dementia risk, the team collected blood samples from all of the participants at the start and end of the training period.

This revealed that, among men, speed training increased the ratio of two forms of beta-amyloid found in the blood, which suggests the training boosted the brain’s ability to clear beta-amyloid 42. This protein forms clumps called plaques in the brain during Alzheimer’s disease, disrupting brain function. The other two kinds of training had no effect.

“It’s a really cool finding,” says  at McGill University in Montreal. “It is definitely strengthening what they’ve [previously] shown with the reduction in dementia.”

Some Alzheimer’s treatments, such as lecanemab, have been designed to help clear amyloid from the brain, but they only marginally slow cognitive decline during Alzheimer’s disease. The limited benefit seen in trials is probably down to these treatments being taken at a relatively late stage of the condition, when substantial brain damage has already occurred, says at University College London.

Engaging in cognitive training to reduce beta-amyloid build-up before dementia develops may have a bigger effect on dementia because it would be done before much brain damage has occurred, says Castegnaro.

However, cognitive training had no effect on amyloid levels in female participants in the study. This suggests that speed training reduces dementia risk in different ways in women and men, says Chai.

The team hopes to explore how speed training may benefit women in future studies, says Chai. But first, the findings need to be verified in geographically and ethnically diverse groups, says Novozhilova.

Global warming-fuelled heat and drought is already hitting yields of maize, wheat and soybeans to the tune of $20 billion a year, a study has estimated. This could rise eightfold, to more than $160 billion by 2100, unless we slash emissions.

While the financial losses will be greatest for big producers such as the US, the impacts will be felt most in the lowest-income countries, where ,��������� at the International Institute for Applied Systems Analysis (IIASA) in Austria. “If you look at the least-developed countries in Africa, the impact is much bigger.” This could lead to social unrest and increased migration, she warns.

There is great uncertainty about these kinds of projections, not least because so much depends on how farmers respond and adapt to a continually changing climate, for instance, by switching to different crops or adopting irrigation where it is possible. In fact, the whole point of this study is to raise awareness and encourage adaptation, to help ensure these projections turn out to be overestimates, says team member , also at IIASA. “This is the entire mission of climate scientists: we make these cases for people to react, so our projections turn out to be wrong.”

The researchers started by gathering data on the yields per country of maize, wheat and soya from the UN Food and Agriculture Organization (FAO). Next, they took past climate data and calculated the drought level, using a standard approach that estimates soil moisture levels from rainfall and evaporation levels.

Past heat extremes and drought levels were then compared with the yields from 1974 to 2004 to estimate the impact of heat and drought. They then used these statistical correlations to estimate crop losses from 2007 to 2019. Their results suggest that increases in heat extremes and drought have caused a 3.5 per cent decline in yields relative to the 1974 to 2004 baseline. “Three per cent or so might not sound like much, but this is a major impact [on] the global food market, which regionally can trigger a severe crisis,” says Kornhuber.

The researchers then calculated the economic losses, based on FAO data showing how much farmers would have been paid for their produce at the time. Finally, they used the same approach to project future losses in several different emissions scenarios, assuming that some adaptation takes place.

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In a high-emissions scenario, known as SSP3-7.0, global yields will fall by around 35 per cent by 2100, with annual losses rising to more than $161 billion. “The production losses caused by heat and drought are around 855 million tonnes a year,” says Hwong, who presented the results at a meeting of the European Geosciences Union in Vienna in May. “I think that is equivalent to what around 2 billion people consume over a year.”

This could be an underestimate of the full impact of climate change for a number of reasons: it’s just three crops, and it doesn’t include flood, storm or rain damage, or the possibility that shortages could lead to big price increases, as is already happening with some other crops such as coffee and cacao.

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at Columbia University in New York says the study’s reliance on the statistical relationships between yield losses and extreme heat and drought could result in it overestimating the impacts by 2100. “Statistical yield models are great for explaining what’s happening now, and in the near past [or] future, but they are inherently unreliable when pushed into vastly different environmental regimes, such as high-emission climate scenarios by the end of the century.” Computer models of how plants are affected by rising CO2 and temperatures are better for projecting what will happen by the end of the century, he says.

at the University of Queensland, Australia, makes the same point. “Although models are not perfect, they are better suited for this type of extrapolation.” However, her team recently released a , which hasn’t been peer-reviewed, showing that two widely used models for wheat make large errors and are especially poor at forecasting the combined effects of extreme heat and drought.

But Kornhuber has defended his team’s use of statistical methods. “The models are remarkable tools, but some of the validation papers have suggested that they might not be super responsive to extremes,” he says. “In our project, extremes were the main focus, so we decided to establish these relationships directly through statistics.”