Narwhals are toothed whales, renowned for their distinctive straight, spiraling tusks, which many people in medieval times believed were the horns of unicorns and thus held magical healing properties. That belief was debunked long ago, but the tusks remain popular souvenirs in Canada and Greenland. And they still hold a fascination for scientists keen to learn more about their unusual structure. A new paper published in the journal Nature Communications reports that rather than one left-oriented spiral, narwhal tusks also have a second internal spiral oriented in the opposite direction.

Inuit legend holds that a woman was dragged into the ocean by a harpoon rope after the weapon had hit a narwhal and was transformed into the animal herself. Her hair, which she'd worn in a twisted knot, became the spiral tusk. The tusk is actually a canine tooth in the left upper jaw of male narwhals, pushing through the lip when the males reach two or three years of age and growing to lengths as long as 1.5 to 2 meters (just under 5 feet to 9 feet 10 inches). Some males may develop two long spiral tusks or, in rare cases, none at all.

There's a general consensus that these tusks most likely evolved via sexual selection as a form of social status. They clearly aren't crucial for survival, since the females usually don't develop the tusk—and if they do, the tusks are much smaller with fewer spirals—and yet typically live longer than the males. But the precise function of the tusk is still a matter of considerable debate.

Narwhals have been observed using them to stun small Arctic cod while hunting. It's possible they are used as weapons in fights, but this behavior hasn't been directly observed, although there have been narwhals found with tusks embedded in their bodies. The presence of several million nerve endings suggests that narwhals may be able to sense temperature or salinity changes in the water with their tusks.

A double helix

Scientists know that the tusk consistently twists in the left-handed direction and that it is composed of dentine covered by a thin layer of cementum encasing a central pulp chamber. The dentine and cementum, in turn, are made up of microscopic collagen fibrils mineralized with nanoparticles of hydroxyapatite. The macroscale spiral shape emerges somehow from how those fibrils organize themselves. That structure also determines the tusk's material properties. One question is whether the helical structure is also present at the micro- and nanoscale.

But nobody had mapped the interior structure in three dimensions at the atomic, nano, and macroscales. So the authors of this latest paper studied two male narwhal tusk and skull specimens by combining multiple imaging techniques: X-ray computed tomography, scanning X-ray diffraction, scanning small-angle X-ray scattering and tensor tomography, and bifringence microscopy. That required reserving time on three large synchrotrons in Sweden, Switzerland, and France. They also performed standard morphological measurements and conducted mechanical three-point bending tests.

The results showed that the collagen fibrils and hydroxyapatite nanoparticles orient themselves along the tusk's longitudinal axis, so there is a consistently high degree of anisotropy at all scales. But there are tiny systemic deviations at small angles in that orientation, which in turn create the twisted structure. While the cementum layer forms the known left-handed helix, the dentine forms a right-handed helix.

That double-helix structure is the secret to the tusk's remarkable stiffness and strength, with the flexible fibers and stiff mineral matrix enabling the tusk to withstand strong forces, like bending and twisting without cracking. It also allows the narwhal tusk to grow straight, unlike, say, an elephant's curved tusk. The team also noted a finer underlying microstructure in the cementum of collagen fiber bundles radially extending outward, which they plan to study further using micro- and nano-beam experiments.

“Since whales can live for up to 80 years, their teeth form a kind of historical record of changing environmental conditions throughout the animal’s lifetime," said co-author Henrik Birkedal of Aarhus University in Denmark. "And because the North Atlantic is currently undergoing very rapid changes, it is obvious to investigate whether we can trace these changes in the hard tissue of the narwhal tusk. That is what we are now working on."

DOI: Nature Communications, 2026. 10.1038/s41467-026-75689-z  (About DOIs).

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Russian tanks have entered battle for the first time with a new active protection system designed to shoot down incoming drones. But the technology’s recent combat debut in Ukraine met with only limited success—Ukrainian drones still destroyed the Russian armored vehicles by attacking in overwhelming numbers.

The first documented battlefield appearance of the Arena-M active protection system took place when Russian forces launched a company-size assault with tanks and other armored vehicles in the Donetsk Oblast of eastern Ukraine on July 22. The Ukrainian defenders repelled the attack and posted video footage of their kamikaze drone strikes destroying at least seven T-72B3A tanks, including some that carried the Arena-M system, according to Euromaidan Press.

However, Ukrainian soldiers also described the Russian Arena-M system successfully shooting down some incoming drones, according to the journalists Dmytro Putiata and Rob Lee. The Ukrainians reported requiring between 15 and 20 drones to finish off each tank.

The incident “demonstrated that the Russian military is learning and is experimenting in how to employ armor on a drone-saturated battlefield,” Lee wrote on X. “The Arena-M [active protection system] demonstrated effectiveness and will likely be improved.”

This development comes more than four years after Russia launched its full-scale invasion of Ukraine in February 2022, as mass armored assaults have become increasingly scarce on the modern battlefield dominated by drone warfare. It’s part of an ongoing arms race where many militaries are struggling to figure out how to protect the weakest points of their expensive main battle tanks and other armored vehicles against swarms of cheap drones.

The Russian military has previously tried adding more physical armor in the form of “cope cages” welded or bolted onto tanks and other vehicles, which inspired the Ukrainian military to do the same. Russian forces even made “turtle tanks” covered in porcupine-style metal spikes and other improvised armor, although the extra weight and encumbrance of such add-ons have often limited both tank mobility and the use of their main guns.

Even up-armored vehicles attempting to enter the drone kill zone usually get destroyed, which is why mechanized assaults have mostly disappeared from the current battlefields in Ukraine in favor of infiltration tactics using small groups of soldiers. Russia’s battlefield deployment of the Arena-M aimed to change that.

The limitations of Arena-M

The Arena-M represents the latest version of the Arena system originally developed in the Soviet era. The technology uses radar to detect incoming rocket-propelled grenades and anti-tank missiles so that it can launch its own projectiles to intercept the incoming warheads.

The Ukrainian news publication Militarnyi reported that Russian engineers have been working to equip their tanks with the Arena-M system since 2019 and that live-fire tests were already being conducted in 2021. However, Militarnyi also highlighted reports suggesting Russia was struggling to adapt the Arena-M system to detect and destroy small drones, because the latter can fly more slowly and in more unpredictable ways than incoming missiles or rockets fired directly at tanks.

Having just a dozen countermunitions for interceptions also proved inadequate in the face of large numbers of Ukrainian drones. Remotely piloted Ukrainian drones capable of disabling or destroying armored vehicles through kamikaze attacks can cost as little as $400 each—so it’s still a very cost-effective trade for Ukrainian drone operators even if they have to use more than 12 drones to take out an armored vehicle costing millions of dollars.

“The Arena-M system, by itself, likely will not be an effective countermeasure to Ukrainian [first-person view drones] alone, as the system can be overwhelmed and only increases the cost and effort required of Ukrainian forces defending against the Russian mechanized assault,” wrote the Institute for the Study of War in an August 9 update on the war in Ukraine.

Pro-Kremlin Russian bloggers apparently acknowledged the Arena-M system's current limitations and called for additional defenses to be integrated to provide tanks with layered air defense against drones. However, tanks and other armored vehicles still face additional battlefield threats beyond drones in the so-called kill zone, including crewed anti-tank weapons, landmines, and artillery.

For now, the Russian military may be considering increasing the number of Arena-M counter munitions to intercept incoming drones and other projectiles. But as Euromaidan Press explained, space constraints for the turret-mounted projectile launchers could ultimately limit that approach.

Concerns beyond the war in Ukraine

The limitations of active protection systems against drones have also appeared beyond the battlefields in Ukraine during the US-Israeli war against Iran. When the Israeli military sent troops into Lebanon to fight the Iranian-backed faction Hezbollah, the Israeli Merkava 4 tanks came equipped with Trophy active protection systems developed by Israel’s Rafael Advanced Defense Systems.

But Hezbollah militants published multiple videos showing their small quadcopter drones loaded with explosives striking Israeli tanks that had Trophy systems still loaded with countermunitions, according to the Ukrainian media company Defense Express. Such videos implied that the Trophy system had difficulty detecting incoming small drones.

Making matters worse for the Israeli military, Hezbollah deployed drones that are immune to radio signal jamming because they are connected to human operators by miles of fiber optic cables. That battlefield innovation first came out of the war in Ukraine and became a crucial part of Hezbollah’s arsenal as the faction ramped up its asymmetric campaign against Israel between March and June 2026, according to the Institute for the Study of War.

Although it’s unclear how many Israeli tanks were damaged or knocked out by Hezbollah’s drones, such drone attacks became the top threat for the Israeli military in Lebanon and accounted for the majority of deaths among Israeli soldiers after a temporary ceasefire went into effect in April, The Wall Street Journal reported.

Despite uncertainty about the Trophy active protection system’s performance, multiple European countries have been buying the Trophy system in an attempt to better protect their tanks against the threat of drones. The EuroTrophy joint venture expects to equip 400 European Leopard tanks with the system, according to Breaking Defense.

The US military has already equipped several hundred M1 Abrams tanks with the Trophy system in recent years. But it’s clear that the United States and many other countries are still sorting out the best way to deploy tanks on drone-dominated battlefields. During the Combined Resolve military exercise held in Germany this year, Ukrainian drone operators wiped out an entire brigade of US Army tanks and armored vehicles.

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Rising costs, slowing tax revenue and a sluggish economy have saddled some of Texas’ biggest cities with multimillion-dollar deficits.

Marcus Martin, center, hugs Austin Police Department Officer Steven Creamer, left, on Thursday, Aug. 6, 2026. Officer Edward Soltys is at right. Officers Creamer and Soltys are part of No Wrong Door, a new initiative seeking to better help some of Austin's most vulnerable. Officers call this process a "warm hand-off," which offers the participant a continuity of care.

During a medieval siege, a trebuchet scored a chance hit one unlucky defender. A small boulder slammed into his upper back at close to 300 kilometers an hour, smashing bones and crushing him beneath its weight.

The man’s skeleton lay beneath the chapel of Scotland’s Stirling Castle, along with the remains of several other people who had clearly died violent deaths. But this one, known to us only as Skeleton 150 (or as “trebuchet guy” in your faithful correspondent’s notes), stood out even among that battle-damaged crowd because most of his upper body had been shattered. According to University of Bradford paleopathologist Jo Buckberry, who presented her research at the 25^th European Meeting of the Paleopathology Association last week, skeleton 150 is the only known trebuchet casualty in history.

A shattered skeleton

Skeleton 150 was in terrible shape, even for a dead guy. The man’s skull had broken in 61 separate places, and another 60 jagged bits of bone were distributed across his ribs. His right shoulder was broken, and his right leg above the knee was basically shattered.

Buckberry and her colleagues threw everything they could, metaphorically speaking, at the jigsaw puzzle of broken bones: forensics, microscopes, X-rays, and micro-CT scans. All of those results pointed to a single moment of crushing impact by something heavy and fast-moving. The pattern of the injuries suggests that the man’s right shoulder and the back of his head caught the brunt of the impact, while his ribs probably cracked under the weight of something heavy slamming him into the ground and pinning him there.

The bones had broken when they were fresh, so it was clearly not a case of “oops, we dropped a big rock on the corpse.” And the amount of force required to do so much damage in a single, shattering blow ruled out several messy possible ways to die during a medieval siege: Skeleton 150 hadn’t been trampled by a horse or run over by a cart, for example. Even if he had fallen from the castle walls, he probably wouldn’t have landed with enough force to do all of that, and the angle would have been all wrong.

"The most similar cases I was finding were car crashes and people hit by trains," Buckberry told Science.org’s Andrew Curry. Assuming Stirling Castle hadn't been attacked by time-travelers, though, that raised new questions. "What is large and moving very quickly in 1304?"

Big rocks flung by trebuchets, that's what.

The physics of throwing big rocks

A trebuchet works a bit like the world's deadliest see-saw; at the long end of the see-saw is the sling that holds the projectile, and at the shorter end is a counterweight (a box of rocks or lead, 10 to 100 times heavier than the projectile). When the counterweight drops, its momentum raises the other end of the see-saw, tossing the sling up in a big arc. And when the sling reaches the end of its length, it stops—but the projectile keeps flying until it hits something.

A typical trebuchet of the time could launch a 90-kilogram projectile (typically a big rock) a few hundred yards. According to this handy medieval trebuchet calculator, that means the projectile would have smashed into Skeleton 150 at somewhere between 200 and 300 kilometers per hour, depending on the exact weight of the projectile and the trebuchet’s counterweight, the length of the sling, and the airspeed velocity of an unladen swallow. That’s an impact with a little over 200 kilojoules of energy.

Trebuchets and other siege engines (we will, under no circumstances, be delving into the distinctions between the different types of catapult) were meant to take out walls and other fortifications. They weren’t antipersonnel weapons; people undoubtedly got injured by flying debris or collapsing structures, but medieval engineers weren’t aiming their catapults at individuals. Skeleton 150 just got terribly unlucky.

"While the use of siege engines is well-documented, we believe this is the first evidence of trebuchet trauma in the archaeological record," wrote Buckberry, adding, "The lack of directly comparable forensic cases remains a limitation."

Please do not, though. Credit: Kiona Smith

Who was Skeleton 150? Scottish, probably

Skeleton 150 was one of nine people found in graves beneath the castle’s medieval chapel, to the surprise of renovation workers, in 1997. Five of the dead had wounds that suggested they had died violent deaths: a middle-aged woman had suffered two heavy blows to the side of her head before falling and being struck with a war-hammer, which left a pair of eerily-neat square holes in the top of her skull. A teenage boy had been stabbed in the chest with a sharp weapon that left its mark on his ribs, then struck hard in the jaw, collarbone, and torso.

It’s hard to say exactly who any of these people were, besides obvious medieval wartime casualties. All five of their remains radiocarbon dated to around the Scottish Wars of Independence in the early 1300s, during which Stirling Castle was hotly contested real estate; it changed hands five times just in the eight years between 1296 and 1304, and the wars carried on until 1357. So some of the people buried in the chapel may have been Scottish, and others may have been English.

At least one of the dead, whose skeleton bore the marks of a lifetime of healed wounds, turned out to be an English knight, Sir John de Stricheley, who died in 1341. The ratio of chemical isotopes in his bones suggested that he had grown up eating food grown on the bedrock of southern England, and that, combined with his age and apparent status, pointed to an English knight. Sir John de Stricheley died at the castle in 1341 (and was important enough to have his death written down properly).

Buried not far from Sir John and the others lay skeleton 150, who Buckberry and her colleagues say was most likely a Scottish defender of the castle killed during the siege of 1304, when King Edward I of England laid siege to Stirling Castle with what Historic Environment Scotland describes as “possibly the largest array of siege engines ever assembled by the kingdom of England.”

Setting the stage

In 1304, Skeleton 150 was probably one of the 25 men, led by Sir William Oliphant, who made up the last gasp of Scottish resistance against England and Edward I. After defeating William "They Will Never Take Our Freedom" Wallace at the Battle of Falkirk in 1298, Edward spent the next six years conquering the rest of Scotland. The country's nobles eventually surrendered in exchange for being allowed to keep their lands (some of them may have done so with their fingers crossed). Edward’s long and bloody campaign was nearly over, except for this one castle, which inconveniently happened to perch along a strategically important road to Edinburgh. And the king was not amused.

In preparation for the siege, Edward decided to flex his newly won power over the Scots, which was undoubtedly as much a political gesture as a strategic choice. He ordered the Scottish nobles who had just surrendered to send him troops and horses for the siege, and he ordered that every church in Scotland strip the lead from their roofs and send it to the siege as well. Thirty-nine carts of lead arrived from around Scotland, mostly from St. Andrew's, along with "all the iron and great stones of Glasgow."

Thirteen siege engines were in place when Edward I arrived on the scene in April of 1304, and they bombarded the castle around the clock for three solid months. Somewhere during those months, Skeleton 150 met a bad end.

The War Wolf, probably not the trebuchet that killed Skeleton 150. Credit: Bob Marshall, HES

The War Wolf

As the siege wore on, Edward I set his engineers and carpenters to work on the largest trebuchet anyone in the world had ever seen. He dubbed it the War Wolf, or Loup de Guerre, and it was an absolute monster—so much so that Oliphant, who had held the castle for three months and still had enough men and provisions to keep antagonizing the king for a while yet, decided that actually, he would very much like to surrender after all, before the giant trebuchet took the field, thank you very much.

And Edward I told him no.

The king was not going to miss the chance to use his tremendous new trebuchet, nor the chance to very publicly and definitively (and also literally) crush the last of the Scottish opposition to his reign. So he ordered his engineers to load the War Wolf and fling a 140-kilogram projectile straight through the castle's curtain wall. Witnesses compared it to watching an arrow pierce a paper target.

It's tempting to speculate that Skeleton 150 might have been a casualty of the infamous War Wolf itself, but that seems unlikely. For one thing, the odds just aren't in favor of the theory; the War Wolf flung a single, albeit enormous, shot on the very last day of the siege. Thirteen other siege engines had been firing at all hours of the day and night for three months before that.

He was probably dead and hastily buried in the chapel by the time the castle walls crumbled and Oliphant and the other survivors were rounded up and taken south to prison in England.

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