A nebulous void in Egypt’s Great Pyramid of Giza has been unveiled thanks to strange subatomic particles called muons.

Scientists first identified the void in 2016 using muons, heavy relatives of electrons that can penetrate through solid materials. Thought to be a corridor-shaped hole, the void was located near a chevron-shaped structure visible on the pyramid’s north face. Further muon measurements revealed new details of the void’s size and shape, scientists from the ScanPyramids team report March 2 in Nature Communications.
The new muon measurements indicate that the void is a 9-meter-long corridor about 2 meters wide by 2 meters tall, close to the pyramid’s north face. ScanPyramids researchers made additional measurements with ground-penetrating radar and ultrasonic testing, they reported March 2 in NDT & E International. The detailed measurements allowed the scientists to use an endoscope to take images inside the chamber, the team announced. The images reveal a corridor with a vaulted ceiling, presumably one that was hasn’t been seen by humans since the pyramid was built more than 4,500 years ago. The corridor’s purpose is still unclear.
Muons are created when high-energy particles from space called cosmic rays crash into the Earth’s atmosphere. Muons are partially absorbed as they rain down onto structures such as the pyramids. Using detectors placed inside the pyramid, scientists from ScanPyramids zeroed in on regions where more muons made it through, indicating they’d traversed less material, which let them map out the location of the void.

Scientists also recently used muons to probe an ancient Chinese wall (SN: 1/30/23), a nuclear reactor and various volcanoes (SN: 4/22/22).

Artificial intelligence has passed the last major milestone in mastering poker: six-player no-limit Texas Hold’em.

Games like poker, with hidden cards and players who bluff, present a greater challenge to AI than games where every player can see the whole board. Over the last few years, computers have become aces at increasingly complicated forms of one-on-one poker, but multiplayer games take that complexity to the next level (SN Online: 5/13/15).

Now, a card shark AI dubbed Pluribus has outplayed more than a dozen elite professionals at six-player Texas Hold’em, researchers report online July 11 in Science. Algorithms that can plot against several adversaries using such spotty information could make savvy business negotiators, political strategists or cybersecurity watchdogs.
Pluribus honed its initial strategy by playing against copies of itself, starting from scratch and gradually learning which actions helped to win. Then, the AI used that intuition for when to hold and when to fold during the first betting round of each hand against five human players.

During subsequent betting rounds, Pluribus fine-tuned its strategy by imagining how the game might play out if it took different actions. Unlike artificial intelligence trained for two-player poker, Pluribus didn’t speculate all the way to the end of the game — which would require too many computations when dealing with so many players (SN: 4/1/17, p. 12). Instead, the AI imagined several moves ahead and decided what to do based on those hypothetical futures and different strategies that players could adopt.

In 10,000 hands of Texas Hold’em, Pluribus competed against five contestants from a pool of 13 professionals, all of whom had won more than $1 million playing poker. Every 100 hands, Pluribus raked in, on average, about $480 from its human competitors.
“This is roughly the amount that elite human professionals aspire to beat weaker players by,” implying that Pluribus was a savvier player than its human opponents, says Noam Brown of Facebook AI Research in New York City. Brown, along with Tuomas Sandholm of Carnegie Mellon University in Pittsburgh, created Pluribus.

Now that AI has poker in the bag, algorithms could test their strategic reasoning in games with more complex hidden information, says computer scientist Viliam Lisý of the Czech Technical University in Prague, who was not involved in the work. In games like Kriegspiel — a chess spin-off where players can’t see each other’s pieces — the unknowns can become far more complicated than a few cards held close to opponents’ chests, Lisý says.

Video games like StarCraft, which allow many more types of moves and free players from rigid, turn-based play, could also serve as new tests of AI cleverness (SN: 5/11/19, p. 34).

A week after two large earthquakes rattled southern California, scientists are scrambling to understand the sequence of events that led to the temblors and what it might tell us about future quakes.

A magnitude 6.4 quake struck July 4 near Ridgecrest — about 194 kilometers northeast of Los Angeles — followed by a magnitude 7.1 quake in the same region on July 5. Both quakes occurred not along the famous San Andreas Fault but in a region of crisscrossing faults in the state’s high desert area, known as the Eastern California Shear Zone.

The San Andreas Fault system, which stretches nearly 1,300 kilometers, generally takes center stage when it comes to California’s earthquake activity. That’s where, as the Pacific tectonic plate and the North American tectonic plate slowly grind past each other, sections of ground can lock together for a time, slowly building up strain until they suddenly release, producing powerful quakes.

For the last few tens of millions of years, the San Andreas has been the primary origin of massive earthquakes in the region. Now overdue for a massive earthquake, based on historical precedent, many people fear it’s only a matter of time before the “Big One” strikes.
But as the July 4 and July 5 quakes — and their many aftershocks — show, the San Andreas Fault system isn’t the only source of concern. The state is riddled with faults, says geophysicist Susan Hough of the U.S. Geological Survey in Pasadena, Calif. That’s because almost all of California is part of the general boundary between the plates. The Eastern California Shear Zone alone has been the source of several large quakes in the last few decades, including the magnitude 7.1 Hector Mine quake in 1999, the magnitude 6.7 Northridge quake in 1994 and the magnitude 7.3 Landers quake in 1992 (SN Online: 8/29/18).

Here are three questions scientists are trying to answer in the wake of the most recent quakes.

Which faults ruptured, and how?
The quakes appear to have occurred along previously unmapped faults within a part of the Eastern California Shear Zone known as the Little Lake Fault Zone, a broad bunch of cracks difficult to map, Hough says. “It’s not like the San Andreas, where you can go out and put your hand on a single fault,” she says. And, she adds, the zone also lies within a U.S. Navy base that isn’t generally accessible to geologists for mapping.

But preliminary data do offer some clues. The data suggest that the first rupture may actually have been a twofer: Instead of one fault rupturing, two connected faults, called conjugate faults, may have ruptured nearly simultaneously, producing the initial magnitude 6.4 quake.

It’s possible that the first quake didn’t fully release the strain on that fault, but the second, larger quake did. “My guess is that they will turn out to be complementary,” Hough says.

The jury is still out, though, says Wendy Bohon, a geologist at the Incorporated Research Institutions for Seismology in Washington, D.C. “What parts of the fault broke, and whether a part of the fault broke twice … I’m waiting to see what the scientific consensus is on that.”
And whether a simultaneous rupture of a conjugate fault is surprising, or may actually be common, isn’t yet clear, she says. “In nature, we see a lot of conjugate fault pairs. I don’t think they normally rupture at the same time — or maybe they do, and we haven’t had enough data to see that.”

Is the center of tectonic action moving away from the San Andreas Fault?
GPS data have revealed exactly how the ground is shifting in California as the giant tectonic plates slide past one another. The San Andreas Fault system bears the brunt of the strain, about 70 percent, those data show. But the Eastern California Shear Zone bears the other 30 percent. And the large quakes witnessed in that region over the last few decades raise a tantalizing possibility, Hough says: We may be witnessing the birth pangs of a new boundary.

“The plate boundary system has been evolving for a long time already,” Hough says. For the last 30 million years or so, the San Andreas Fault system has been the primary locus of action. But just north of Santa Barbara lies the “big bend,” a kink that separates the northern from the southern portion of the fault system. Where the fault bends, the Pacific and North American plates aren’t sliding sideways past one another but colliding.

“The plates are trying to move, but the San Andreas is actually not well aligned with that motion,” she says. But the Eastern California Shear Zone is. And, Hough says, there’s some speculation that it’s a new plate boundary in the making. “But it would happen over millions of years,” she adds. “It’s not going to be in anyone’s lifetime.”

Will these quakes trigger the Big One on the San Andreas?
Such large quakes inevitably raise these fears. Historically, the San Andreas Fault system has produced a massive quake about every 150 years. But “for whatever reason, it has been pretty quiet in the San Andreas since 1906,” when an estimated magnitude 7.9 quake along the northern portion of the fault devastated San Francisco, Hough says. And the southern portion of San Andreas is even more overdue for a massive quake; its last major event was the estimated magnitude 7.9 Fort Tejon quake in 1857, she says.

The recent quakes aren’t likely to change that situation. Subsurface shifting from a large earthquake can affect strain on nearby faults. But it’s unlikely that the quakes either relieved stress or will ultimately trigger another earthquake along the San Andreas Fault system, essentially because they were too far away, Hough says. “The disruption [from one earthquake] of other faults decreases really quickly with distance,” she says (SN Online: 3/28/11).

Some preliminary data do suggest that the magnitude 7.1 earthquake produced some slippage, also known as creep, along at least one shallow fault in the southern part of the San Andreas system. But such slow, shallow slips don’t produce earthquakes, Hough says.

However, the quakes could have more significantly perturbed much closer faults, such as the Garlock Fault, which runs roughly west to east along the northern edge of the Mojave Desert. That’s not unprecedented: The 1992 Landers quake may have triggered a magnitude 5.7 quake two weeks later along the Garlock Fault.

“Generations of graduate students are going to be studying these events — the geometry of the faults, how the ground moved,” even how the visible evidence of the rupture, scarring the land surface, erodes over time and obscures its traces, Bohon says.

At the moment, scientists are eagerly trading ideas on social media sites. “It’s the equivalent of listening in on scientists shouting down the hallway: ‘Here’s my data — what do you have?’ ” she says. Those preliminary ideas and explanations will almost certainly evolve as more information comes in, she adds. “It’s early days yet.”

Homo sapiens who reached Europe around 54,000 years ago introduced bows and arrows to that continent, a new study suggests.

Researchers examined tiny triangular stone points and other artifacts excavated at a rock-shelter in southern France called Grotte Mandrin. H. sapiens on the move probably brought archery techniques from Africa to Europe, archaeologist Laure Metz of Aix-Marseille University in France and colleagues report February 22 in Science Advances.

“Metz and colleagues demonstrate bow hunting [at Grotte Mandrin] as convincingly as possible without being caught bow-in-hand,” says archaeologist Marlize Lombard of the University of Johannesburg, who did not participate in the new study.
No bows were found at the site. Wooden items such as bows preserve poorly. The oldest intact bows, found in northern European bogs, date to around 11,000 years ago, Metz says.

Previous stone and bone point discoveries suggest that bow-and-arrow hunting originated in Africa between about 80,000 and 60,000 years ago. And previously recovered fossil teeth indicate that H. sapiens visited Grotte Mandrin as early as 56,800 years ago, well before Neandertals’ demise around 40,000 years ago and much earlier than researchers had thought that H. sapiens first reached Europe (SN: 2/9/22).

“We’ve shown that the earliest known Homo sapiens to migrate into Neandertal territories had mastered the use of the bow,” Metz says.

No evidence suggests that Neandertals already present in Europe at that time launched arrows at prey. It’s also unclear whether archery provided any substantial hunting advantages to H. sapiens relative to spears that were thrust or thrown by Neandertals.
Among 852 stone artifacts excavated in a H. sapiens sediment layer at Grotte Mandrin dated to about 54,000 years ago, 196 triangular stone points displayed high-impact damage. Another 15 stone points showed signs of both high-impact damage and alterations caused by butchery activities, such as cutting.

Comparisons of those finds were made to damage on stone replicas of the artifacts that the researchers used as arrowheads shot from bows and as the tips of spears inserted in handheld throwing devices. Additional comparative evidence came from stone and bone arrowheads used by recent and present-day hunting groups.

Impact damage along the edges of stone points from the French site indicated that these implements had been attached at the bottom to shafts.

The smallest Grotte Mandrin points, many with a maximum width of no more than 10 millimeters, could have pierced animals’ hides only when shot from bows as the business ends of arrows, the researchers say. Experiments they conducted with replicas of the ancient stone points found that stone points less than 10 millimeters wide reach effective hunting speeds only when attached to arrow shafts propelled by a bow.

Larger stone points, some of them several times the size of the smaller points, could have been arrowheads or might have tipped spears that were thrown or thrust by hand or launched from handheld spear throwers, the researchers conclude.

Lombard, the University of Johannesburg archaeologist, suspects that the first H. sapiens at the French rock-shelter hunted with bows and arrows as well as with spears, depending on where and what they were hunting. Earlier studies directed by Lombard indicated that sub-Saharan Africans similarly alternated between these two types of hunting weapons starting between about 70,000 and 58,000 years ago.

H. sapiens newcomers to Europe may have learned from Neandertals that spear hunting in large groups takes precedence on frigid landscapes, where bow strings can easily snap and long-distance pursuit of prey is not energy efficient, Lombard says.

But learning about archery from H. sapiens may not have been in the cards for Neandertals. Based on prior analyses of brain impressions on the inside surfaces of fossil skulls, Lombard suspects that Neandertals’ brains did not enable the enhanced visual and spatial abilities that H. sapiens exploited to hunt with bows and arrows.

That’s a possibility, though other controversial evidence suggests that Neandertals behaved no differently from Stone Age H. sapiens (SN: 3/26/20).If Grotte Mandrin Neandertals never hunted with bows and arrows but still survived just fine alongside H. sapiens archers for roughly 14,000 years, reasons for Neandertals’ ultimate demise remain as mysterious as ever.

The James Webb Space Telescope’s first peek at the distant universe unveiled galaxies that appear too big to exist.

Six galaxies that formed in the universe’s first 700 million years seem to be up to 100 times more massive than standard cosmological theories predict, astronomer Ivo Labbé and colleagues report February 22 in Nature. “Adding up the stars in those galaxies, it would exceed the total amount of mass available in the universe at that time,” says Labbé, of the Swinburne University of Technology in Melbourne, Australia. “So you know that something is afoot.”
The telescope, also called JWST, released its first view of the early cosmos in July 2022 (SN: 7/11/22). Within days, Labbé and his colleagues had spotted about a dozen objects that looked particularly bright and red, a sign that they could be massive and far away.

“They stand out immediately, you see them as soon as you look at these images,” says astrophysicist Erica Nelson of the University of Colorado Boulder.

Measuring the amount of light each object emits in various wavelengths can give astronomers an idea of how far away each galaxy is, and how many stars it must have to emit all that light. Six of the objects that Nelson, Labbé and colleagues identified look like their light comes from no later than about 700 million years after the Big Bang. Those galaxies appear to hold up to 10 billion times the mass of our sun in stars. One of them might contain the mass of 100 billion suns.

“You shouldn’t have had time to make things that have as many stars as the Milky Way that fast,” Nelson says. Our galaxy contains about 60 billion suns’ worth of stars — and it’s had more than 13 billion years to grow them. “It’s just crazy that these things seem to exist.”

In the standard theories of cosmology, matter in the universe clumped together slowly, with small structures gradually merging to form larger ones. “If there are all these massive galaxies at early times, that’s just not happening,” Nelson says.

One possible explanation is that there’s another, unknown way to form galaxies, Labbé says. “It seems like there’s a channel that’s a fast track, and the fast track creates monsters.”

But it could also be that some of these galaxies host supermassive black holes in their cores, says astronomer Emma Curtis-Lake of the University of Hertfordshire in England, who was not part of the new study. What looks like starlight could instead be light from the gas and dust those black holes are devouring. JWST has already seen a candidate for an active supermassive black hole even earlier in the universe’s history than these galaxies are, she says, so it’s not impossible.
Finding a lot of supermassive black holes at such an early era would also be challenging to explain (SN: 3/16/18). But it wouldn’t require rewriting the standard model of cosmology the way extra-massive galaxies would.

“The formation and growth of black holes at these early times is really not well understood,” she says. “There’s not a tension with cosmology there, just new physics to be understood of how they can form and grow, and we just never had the data before.”

To know for sure what these distant objects are, Curtis-Lake says, astronomers need to confirm the galaxies’ distances and masses using spectra, more precise measurements of the galaxies’ light across many wavelengths (SN: 12/16/22).

JWST has taken spectra for a few of these galaxies already, and more should be coming, Labbé says. “With luck, a year from now, we’ll know a lot more.”

Blurry vision sounds like a reason to visit an eye doctor. But visual fuzziness might actually help some animals catch dinner. Out-of-focus areas created by vertically elongated pupils help predators triangulate the distance to objects, scientists propose August 7 in Science Advances. Prey animals may gain different visual advantages from pupil shapes that provide panoramic views.

Cats, foxes and many other predators that ambush prey have vertical pupils. Through these narrow slits, vertical objects appear sharp over great distances, the scientists report. Horizontal shapes are clear over a more limited distance, quickly going out of focus as an object moves farther away. This rapidly blurring vision should make it easy to detect even subtle changes in distance, the researchers say. That makes blur a good estimate of distance, says study author Martin Banks, a vision scientist at the University of California, Berkeley. A stalking predator might rely upon an object’s fuzziness to judge its location.
The benefits of this mix of visual cues make good sense, says Michael Land, a neurobiologist at the University of Sussex in Brighton, England. A predator that must pounce on its dinner needs to be able to accurately judge distances, he says.
Many herbivores, like horses and deer, have horizontal, rectangular pupils, rather than vertical slits. The authors don’t think these pupils help with depth perception. But rectangular pupils probably have their own advantages, the authors report, including better panoramic vision and shielding of potentially blinding overhead light. These benefits could help grazing prey spot – and flee from – an approaching slit-eyed hunter.
These visual benefits could explain why predators and prey evolved their pupil shapes, Banks’ team says. But vision scientist Ronald Kröger of Lund University in Sweden warns against assuming that an animal’s habits caused the evolution of a certain pupil shape. Counterexamples exist of predators without slit pupils and herbivores with them, he says. Additionally, many predators and prey animals, including most birds – which were excluded from the study’s analysis – have circular pupils.

But evolution is complex, and the new hypotheses about the advantages of pupil shape only address one aspect of the evolution of vision, Banks says. “There are multiple forces that push the eye to evolve in multiple ways.”

Whether it’s Katy Perry poaching dancers from once-BFF Taylor Swift or Clytemnestra orchestrating the murder of her husband Agamemnon, betrayal is a dark, persistent part of the human condition. Unlike garden-variety deception, betrayal happens in established relationships, destroying trust that has developed over time. It’s usually unexpected, and it yields a unique, often irreparable, wound. In fact, betrayers have a special place in hell, literarily: In Dante’s Inferno, they occupy the ninth and final circle; mere fraudsters dwell in the eighth.

While most of us are familiar with betrayal, investigating it is really hard. (Consider all the complications of a study that asks people in trusted relationships to betray each other.) Case studies of real betrayals can provide insight after-the-fact, but without a time machine, finding studies that reveal big picture patterns about the lead-up to treachery are scarce.

“We all know betrayal exists,” says Cristian Danescu-Niculescu-Mizil, a computer scientist at Cornell University who spends a lot of time thinking about what language reveals about relationships. “But finding relevant data is really hard.”

So when Danescu-Niculescu-Mizil heard about a Diplomacy, a strategy game rife with betrayal, he figured it might serve as a good proxy for real life treachery. And he was right: Studying the patterns of communication between the players revealed that betrayal is sometimes foreseeable. But like many relationships that collapse in betrayal, teasing out what goes wrong and who is at fault isn’t so easy.
Unlike Risk and other war games, Diplomacy is all about, well, diplomacy (John F. Kennedy and Henry Kissinger reportedly were fans). Set in Europe before World War I, the nations/players have to form alliances to win. But chance is removed from the equation; players don’t roll dice or take turns. There’s only diplomacy: a negotiation phase where players converse, form alliances and gather intelligence (these days, typically online), and a movement phase where everyone’s decisions are revealed and executed all at once. Betrayal is so integral to Diplomacy that, as noted on a “This American Life” episode, stabbing an ally in the back is referred to by the shorthand “stabbing.”

Danescu-Niculescu-Mizil, colleague and fan-of-the-game Jordan Boyd-Graber, and colleagues examined 249 games of Diplomacy with a total of 145,000 messages among players. When they used a computer program to compare exchanges between players whose relationships ended in betrayal with those whose relationships lasted, the computer discerned subtle signals of impending betrayal.

One harbinger was a shift in politeness. Players who were excessively polite in general were more likely to betray, and people who were suddenly more polite were more likely to become victims of betrayal, study coauthor and Cornell graduate student Vlad Niculae reportedJuly 29 at the Annual Meeting of the Association for Computational Linguistics in Beijing. Consider this exchange from one round:

Germany: Can I suggest you move your armies east and then I will support you? Then next year you move [there] and dismantle Turkey. I will deal with England and France, you take out Italy.

Austria: Sounds like a perfect plan! Happy to follow through. And—thank you Bruder!

Austria’s next move was invading German territory. Bam! Betrayal.

An increase planning-related language by the soon-to-be victim also indicated impending betrayal, a signal that emerges a few rounds before the treachery ensues. And correspondence of soon-to-be betrayers had an uptick in positive sentiment in the lead-up to their breach.
Working from these linguistic cues, a computer program could peg future betrayal 57 percent of the time. That might not sound like much, but it was better than the accuracy of the human players, who never saw it coming. And remember that by definition, a betrayer conceals the intention to betray; the breach is unexpected (that whole trust thing). Given that inherent deceit, 57 percent isn’t so bad.

When I spoke to Danescu-Niculescu-Mizil, he said that more important than the clues themselves is the shift in the balance of behavior in the relationship. Positive or negative sentiment of one player isn’t what matters, it’s the asymmetry of the behavior of the two people in the relationship. He likens the linguistic tells to body language: While you wouldn’t use it as a sole basis for decision-making, if you know how to interpret it, it might give you an advantage.

More work is needed to explore whether these patterns exist in real life. And while the research did reveal some patterns, it can’t say anything about cause and effect or who is at fault. Perhaps, for example, the extensive planning of the eventual victims came off as super bossy and frustrating to the eventual betrayer. After all, Clytemnestra’s betrayal of Agamemnon came after he killed their daughter Iphigenia. That kind of bad blood may be unforgivable.

Particles of twisted light that have been entangled using quantum mechanics offer a new approach to dense and secure data storage.

Holograms that produce 3-D images and serve as security features on credit cards are usually made with patterns laid down with beams of laser light. In recent years, physicists have found ways to create holograms with entangled photons instead. Now there is, literally, a new twist to the technology.

Entangled photons that travel in corkscrew paths have resulted in holograms that offer the possibility of dense and ultrasecure data encryption, researchers report in a study to appear in Physical Review Letters.
Light can move in a variety of ways, including the up-and-down and side-to-side patterns of polarized light. But when it carries a type of rotation known as orbital angular momentum, it can also propagate in spirals that resemble twisted rotini pasta.

Like any other photons, the twisted versions can be entangled so that they essentially act as one entity. Something that affects one of an entangled photon pair instantly affects the other, even if they are very far apart.

In previous experiments, researchers have sent data through the air in entangled pairs of twisted photons (SN: 8/5/15). The approach should allow high-speed data transmission because light can come with different amounts of twist, with each twist serving as a different channel of communication.

Now the same approach has been applied to record data in holograms. Instead of transmitting information on multiple, twisted light channels, photon pairs with different amounts of twist create distinct sets of data in a single hologram. The more orbital angular momentum states involved, each with different amounts of twist, the more data researchers can pack into a hologram.

In addition to cramming more data into holograms, increasing the variety of twists used to record the data boosts security. Anyone who wants to read the information out needs to know, or guess, how the light that recorded it was twisted.

For a hologram relying on two types of twist, says physicist Xiangdong Zhang of the Beijing Institute of Technology, you would have to pick the right combination of the twists from about 80 possibilities to decode the data. Bumping that up to combinations of seven distinct twists leads to millions of possibilities. That, Zhang says, “should be enough to ensure our quantum holographic encryption system has enough security level.”
The researchers demonstrated their technique by encoding words and letters in holograms and reading the data back out again with twisted light. Although the researchers produced images from the holographic data, says physicist Hugo Defienne of the Paris Institute of Nanosciences, the storage itself should not be confused with holographic images.

Defienne, who was not involved with the new research, says that other quantum holography schemes, such as his efforts with polarized photons, produce direct images of objects including microscopic structures.

“[Their] idea there is very different . . . from our approach in this sense,” Defrienne says. “They’re using holography to store information,” rather than creating the familiar 3-D images that most people associate with holograms.

The twisted light data storage that Zhang and his colleagues demonstrated is slow, requiring nearly 20 minutes to decode an image of the acronym “BIT,” for the Beijing Institute of Technology where the experiments were performed. And the security that the researchers have demonstrated is still relatively low because they included only up to six forms of twisted light in their experiments.

Zhang is confident that both limitations can be overcome with technical improvements. “We think that our technology has potential application in quantum information encryption,” he says, “especially quantum image encryption.”

The photosynthesizing plankton Emiliania huxleyi has a dramatic relationship with its bacterial frenemies. These duplicitous bugs help E. huxleyi in exchange for nutrients until it becomes more convenient to murder and eat their hosts. Now, scientists have figured out how these treacherous bacteria decide to turn from friend to foe.

One species of these bacteria appears to keep tabs on health-related chemicals produced by E. huxleyi, researchers report January 24 in eLife. The bacteria maintain their friendly facade until their hosts age and weaken, striking as soon as the vulnerable algae can’t afford to keep bribing them with nutrients. The finding could help explain how massive algal blooms come to an end.
The bacteria is “first establishing what we call the ‘first handshake,’” says marine microbiologist Assaf Vardi of the Weizmann Institute of Science in Rehovot, Israel. “Then it will shift into a pathogen.”

E. huxleyi’s partnership with these bacteria, which belong to a group called Roseobacter, might be best described as a love-hate relationship. The single-celled alga can’t produce the B vitamins it needs on its own, so it offers up nutrients to lure in Roseobacter that can (SN: 7/8/16). The trade is win-win — at least until the bacteria decide they’d be better off slaying and devouring their algal hosts than sticking around in peaceful coexistence.

Sometimes called the “Jekyll-and-Hyde” trait, this kind of bacterial backstabbery shows up everywhere from animal guts to the open seas. But it wasn’t clear before how Roseobacter decide it’s the right moment to murder E. huxleyi.

Vardi’s team exposed a type of Roseobacter that lives with E. huxleyi to chemicals taken from algae that were either young and growing or old and stagnant. The team also introduced the bacteria to extra doses of a certain health-signaling algal chemical.Looking at which genes the bacteria activated in the different experiments revealed how and why they switched from friend to foe.

The bacteria kill their algal pals when exposed to high concentrations of a sulfur-containing chemical called DMSP, the researchers found. E. huxleyi leaks more and more DMSP as it ages. This eventually cues its duplicitous microbial partners to go rogue, kill their aging host, and kick their genes for nutrient-grabbing proteins and flagella — whiplike tails used to swim — into overdrive.

It’s an “eat-and-run strategy,” says Noa Barak-Gavish, a microbiologist at ETH Zurich. “You eat up whatever you can and then swim away to avoid competition … [and] to find alternative hosts.”

DMSP isn’t the only figure in this deadly chemical calculus. E. huxleyi can sate its companion’s bloodlust with a bribe of benzoate, a nutrient that Roseobacter can use but most bacteria can’t.

While it’s clearer now what drives the bacteria to kill their hosts, their murder weapon remains a mystery. Vardi says his group has some hunches to follow up on.

This kind of frenemies relationship could be a key factor in controlling the boom and bust of massive algal blooms if other phytoplankton and bacteria have a similar dynamic, says Mary Ann Moran of the University of Georgia in Athens, who was not involved in the study. Algal blooms can be toxic (SN: 8/28/18). But they also “fix” enormous amounts of carbon dioxide into biomass and are a major source of organic carbon to the ocean.
“Phytoplankton fix half of all the carbon on the planet, and probably 20 percent to 50 percent of what they fix … actually goes right to bacteria,” she says. So if this kind of relationship controls how carbon flows through the ocean, “that is something that we would really like to understand.”

Vikings brought horses and dogs to the British Isles from Scandinavia, a new study suggests.

A chemical analysis of bone fragments from a cemetery in England provides the first solid scientific evidence of animals traveling with Vikings across the North Sea, scientists report February 1 in PLOS ONE.

In the 1990s, researchers unearthed the cremated remains of a human adult and child as well as of a dog, horse and probable pig from a burial mound in a Viking cemetery in Derbyshire, England. In previous work, radiocarbon dating of femur, skull and rib fragments revealed that the inhabitants all died sometime between the eighth and 10th centuries. That date was narrowed down to the year 873, thanks to the ninth-century Anglo-Saxon Chronicle, which records that a Viking army wintered near the site that year.
Where the animals came from has been a mystery. Norse raiders are known to have stolen horses from people in England around the time. And researchers have generally thought that Viking boats at the time were too small to allow for much transport of animals from Scandinavia to the British Isles. One entry in the Anglo-Saxon Chronicle describes Vikings moving from France to England along with their horses in the year 892, but no physical evidence of such activity had been found before.

In the new work, Tessi Löffelmann and colleagues turned to certain forms, or isotopes, of strontium to unravel the individuals’ provenance. The element accumulates in bones over time through diet, leaving a distinct signature of where an individual has lived (SN: 4/2/19).
Strontium ratios in the child’s remains matched those of shrubs growing at the burial site, suggesting the child spent most, if not all, of its life in England. The ratios of the adult and three animals, on the other hand, differed substantially from the local fauna, the team found. That suggests the individuals hadn’t spent much time in the country before they died. Instead, their ratios were similar to ones found in the Baltic Shield region in Norway, central and northern Sweden and Finland, suggesting a Scandinavian origin.

“One of the joys of isotope analysis is that you are able to really pinpoint things that previously we could discuss endlessly,” says Marianne Moen, an archeologist at the University of Oslo who was not involved in the study. Using strontium to analyze more cremated remains, which can elude common forms of isotope analysis including carbon and nitrogen, “is the next logical chapter for understanding prehistoric mobility.”

Isotope analysis helped reveal where these individuals lived and when they died, but it couldn’t answer why the dog, horse and pig made the journey to England in the first place. That’s where historical records can help, says Löffelmann, of Durham University in England and Vrije Universiteit Brussel in Belgium.

For Löffelmann, the small sizes of early Norse ships combined with the fact that the animals and people were buried together suggest Vikings may have initially brought animals with them for companionship, not just function.

“It could have only been selected animals that made that journey,” she says. “They were important to what the person was.… They went through life together, and now they’re going through death.”