SAN DIEGO — A remote planet — the first with hints of a limestone shell — has been shredded by its dead sun, a new study suggests.

A generous heaping of carbon is raining down on a white dwarf, the exposed core of a dead star, astrophysicist Carl Melis of the University of California, San Diego said June 13 at a meeting of the American Astronomical Society. The carbon — along with a dash of other elements such as calcium, silicon and iron — is probably all that remains of a rocky planet, torn apart by its dying sun’s gravity. Many other white dwarfs show similar signs of planetary cannibalism (SN Online: 10/21/15), but none are as flooded with carbon atoms as this one.

A planet slathered in calcium carbonate, a mineral found in limestone, could explain the shower of carbon as well as the relative amounts of other elements, said Melis. He and Patrick Dufour, an astrophysicist at the University of Montreal, estimate that calcium carbonate could have made up to 9 percent of the doomed world’s mass.

While a limestone-encrusted world is a first, it’s not shocking, says Melis. The recipe for calcium carbonate is just carbon and calcium in the presence of water. “If you have those conditions, it’s going to form,” he says.

“The real interesting thing is the carbon,” Melis adds. Carbon needs to be frozen — most likely as carbon dioxide — to be incorporated into a forming planet. But CO2 freezes far from a star, beyond where researchers suspect rocky planets are assembled. A limestone planet could have formed in an unexpected place and later wandered in while somehow retaining its carbon stores in the warm environs closer to its sun. Or the carbon might have been delivered to the world after it formed. But, Melis says, it’s not clear how either would happen.

The Rev. Thomas Bayes was, as the honorific the Rev. suggests, a clergyman. Too bad he wasn’t a lawyer. Maybe if he had been, lawyers today wouldn’t be so reluctant to enlist his mathematical insights in the pursuit of justice.

In many sorts of court cases, from whether talcum powder causes ovarian cancer to The People v. O.J. Simpson, statistics play (or ought to play) a vital role in evaluating the evidence. Sometimes the evidence itself is statistical, as with the odds of a DNA match or the strength of a scientific research finding. Even more often the key question is how evidence should be added up to assess the probability of guilt. In either circumstance, the statistical methods devised by Bayes are often the only reasonable way of drawing an intelligent conclusion.

Yet the courts today seem suspicious of statistics of any sort, and not without reason. In several famous cases, flawed statistical reasoning has sent innocent people to prison. But in most such instances the statistics applied in court have been primarily the standard type that scientists use to test hypotheses (producing numbers for gauging “statistical significance”). These are the same approaches that have been so widely criticized for rendering many scientific results irreproducible. Many experts believe Bayesian statistics, the legacy of a paper by Bayes published posthumously in 1763, offers a better option.

“The Bayesian approach is especially well suited for a broad range of legal reasoning,” write mathematician Norman Fenton and colleagues in a recent paper in the Annual Review of Statistics and Its Application.

But Bayes has for the most part been neglected by the legal system. “Outside of paternity cases its impact on legal practice has been minimal,” say Fenton, Martin Neil and Daniel Berger, all of the School of Electronic Engineering and Computer Science at Queen Mary University London.

That’s unfortunate, they contend, because non-Bayesian statistical methods have severe shortcomings when applied in legal contexts. Most famously, the standard approach is typically misinterpreted in a way known as the “prosecutor’s fallacy.”

In formal logical terms, the prosecutor’s fallacy is known as “the error of the transposed conditional,” as British pharmacologist David Colquhoun explains in a recent blog post. Consider a murder on a hypothetical island, populated by 1,000 people. Police find a DNA fragment at the crime scene, a fragment that would be found in only 0.4 percent of the population. For no particular reason, the police arrest Jack and give him a DNA test. Jack’s DNA matches the crime scene fragment, so he is charged and sent to trial. The prosecutor proclaims that since only 0.4 percent of innocent people have this DNA fragment, it is 99.6 percent certain that Jack is the killer — evidence beyond reasonable doubt.
But that reasoning is fatally (for Jack) flawed. Unless there was some good reason to suspect Jack in the first place, he is just one of 1,000 possible suspects. Among those 1,000, four people (0.4 percent) should have the same DNA fragment found at the crime scene. Jack is therefore just one of four possibilities to be the murderer — so the probability that he’s the killer is merely 25 percent, not 99.6 percent.

Bayesian reasoning averts this potential miscarriage of justice by including the “prior probability” of guilt when calculating the probability of guilt after the evidence is in.

Suppose, for instance, that the crime in question is not murder, but theft of cupcakes from a bakery employing 100 people. Security cameras reveal 10 employees sneaking off with the cupcakes but without a good view of their identities. So the prior probability of any given employee’s guilt is 10 percent. Police sent to investigate choose an employee at random and conduct a frosting residue test known to be accurate 90 percent of the time. If the employee tests positive, the police might conclude there is therefore a 90 percent probability of guilt. But that’s another example of the prosecutor’s fallacy — it neglects the prior probability. Well-trained Bayesian police would use the formula known as Bayes’ theorem to calculate that given a 10 percent prior probability, 90 percent reliable evidence yields an actual probability of guilt of only 50 percent.

You don’t even need to know Bayes’ formula to reason out that result. If the test is 90 percent accurate, it will erroneously identify nine out of the 90 innocent employees as guilty, and it would identify only nine out of the 10 truly guilty employees. If the police tested all 100 people, then, 18 would appear guilty, but nine of those 18 (half of them) would actually be innocent. So a positive frosting test means only a 50 percent chance of guilt. Bayesian math would in this case (and in many real life cases) prevent a rush to injustice.

“Unfortunately, people without statistical training — and this includes most highly respected legal professionals — find Bayes’ theorem both difficult to understand and counterintuitive,” Fenton and colleagues lament.

One major problem is that real criminal cases are rarely as simple as the cupcake example. “Practical legal arguments normally involve multiple hypotheses and pieces of evidence with complex causal dependencies,” Fenton and colleagues note. Adapting Bayes’ formula to complex situations is not always straightforward. Combining testimony and various other sorts of evidence requires mapping out a network of interrelated probabilities; the math quickly can become much too complicated for pencil and paper — and, until relatively recently, even for computers.

“Until the late 1980s there were no known efficient computer algorithms for doing the calculations,” Fenton and colleagues point out.

But nowadays, better computers — and more crucially, better algorithms — are available to compute the probabilities in just the sorts of complicated Bayesian networks that legal cases present. So Bayesian math now provides the ideal method for weighing competing evidence in order to reach a sound legal judgment. Yet the legal system seems unimpressed.

“Although Bayes is the perfect formalism for this type of reasoning, it is difficult to find any well-reported examples of the successful use of Bayes in combining diverse evidence in a real case,” Fenton and coauthors note. “There is a persistent attitude among some members of the legal profession that probability theory has no role in the courtroom.”

In one case in England, in fact, an appeals court denounced the use of Bayesian calculations, asserting that members of the jury should apply “their individual common sense and knowledge of the world” to the evidence presented.

Apart from the obvious idiocy of using common sense to resolve complex issues, the court’s call to apply “knowledge of the world” to the evidence is exactly what Bayesian math does. Bayesian reasoning provides guidance for applying prior knowledge properly in assessing new knowledge (or evidence) to reach a sound conclusion. Which is what the judicial system is supposed to do.

Bayesian statistics offers a technical tool for avoiding fallacious reasoning. Lawyers should learn to use it. So should scientists. And then maybe then someday justice will be done, and science and the law can work more seamlessly together. But as Fenton and colleagues point out, there remain “massive cultural barriers between the fields of science and law” that “will only be broken down by achieving a critical mass of relevant experts and stakeholders, united in their objectives.”

WASHINGTON — To human thinking, songbird nests now seem to have evolved backwards: The most distant ancestor probably built complex, roofed structures. Simple open-top cup nests came later.

More than 70 percent of songbird species today build some form of that iconic open cup, evolutionary biologist Jordan Price said August 18 at the North American Ornithological Conference. Yet looking at patterns of nest style across recent bird family trees convinced him that the widespread cup style probably isn’t just a leftover from deepest bird origins.
Old bird lineages thought to have branched out near the base of the avian family tree tend to have plentiful roof-builders. Price, of St. Mary’s College of Maryland, and coauthor Simon Griffith of Macquarie University in Sydney reconstructed probable nest styles for various branching points in the tree. That reconstruction suggests that open cups showed up independently four times among songbirds, such as in bowerbirds and honeyeaters, the scientists conclude. Also, here and there, some of the earlier cup builders reverted to roofs.

Price said he began musing about nest history while reveling in Australia’s birds during a sabbatical with Griffith. Evolutionary biologists have proposed that the broader Australasia region was probably the starting point for the rise of songbirds. Price said that it isn’t clear what drove a switch from protective roofs to what looks like the quick and dirty alternative of open cups.

Swirling clouds blanket Jupiter’s northern and southern poles in the first closeup images of the planet taken by NASA’s Juno spacecraft. Such intimate views of Jupiter have never been seen before.

Juno snapped a shot of the gas giant’s northern side in an August 27 flyby, from a distance of 195,000 kilometers. The prominent bands that ring Jupiter’s middle fade at the poles, replaced with hurricane-like whorls. The poles are nearly invisible from Earth, making a specialized space mission like Juno necessary to capture such rare images.
Jupiter’s poles are unlike those of its fellow gas giant, Saturn. That planet has a giant cyclone encircling each of its poles (SN: 11/8/08, p. 9).

During the flyby, Juno’s eight science instruments were furiously collecting data. An infrared camera imaged Jupiter’s southern aurora, observing the phenomenon in detail for the first time. And another instrument recorded 13 hours of radio emissions from Jupiter’s auroras, which scientists converted into an eerie-sounding audio clip (listen to the audio clip in video below).

Juno is designed to study Jupiter’s interior, to better understand what lies beneath its clouds (SN: 6/25/16, p. 16). The spacecraft arrived at Jupiter on July 4. Its science instruments were switched off during its approach, so this is the first nearby glimpse scientists have seen. Juno will perform 37 orbits of Jupiter during its mission.

On the dock in Buenaventura, Colombia, the fisherman needed help identifying his catch. “I don’t have any clue what this is,” he said, holding a roughly 50-centimeter-long, grayish-brown fish. Gustavo Castellanos-Galindo, a fish ecologist, recalls the conversation from last October. “I said, ‘Well, this is a cobia, and it shouldn’t be here.’ ”

The juvenile cobia had probably escaped from a farm off the coast of Ecuador that began operating earlier in 2015, Castellanos-Galindo and colleagues at the World Wildlife Fund in Cali, Colombia, reported in March in BioInvasions Records. Intruders had probably cut a net cage, perhaps intending to catch and sell the fish. Roughly 1,500 cobia fled, according to the aquaculture company Ocean Farm in Manta, Ecuador, which runs the farm. Cobia are fast-swimming predators that can migrate long distances and grow to about 2 meters long. The species is not native to the eastern Pacific, but since the escape, the fugitives have been spotted from Panama to Peru.
The cobia getaway is not an isolated incident. Aquaculture, the farming of fish and other aquatic species, is rapidly expanding — both in marine and inland farms. It has begun to overtake wild-catch fishing as the main source of seafood for the dinner table. Fish farmed in the ocean, such as salmon, sea bass, sea bream and other species, are raised in giant offshore pens that can be breached by storms, predators, fish that nibble the nets, employee error and thieves. Global numbers for escapes are hard to come by, but one study of six European countries over three years found that nearly 9 million fish escaped from sea cages, according to a report published in Aquaculture in 2015.

Researchers worry that these releases could harm wildlife, but they don’t have a lot of data to measure long-term effects. Many questions remain. A study out of Norway published in July suggests that some domesticated escapees have mated extensively with wild fish of the same species, which could weaken the wild population. Scientists also are investigating whether escaped fish could gobble up or displace native fish.

Worst-case scenario: Escaped fish spread over large areas and wreak havoc on other species. From toxic toads overrunning Australia and Madagascar (SN Online: 2/22/16) to red imported fire ants in the United States, invasive species are one of the planet’s biggest threats to biodiversity, and they cost billions of dollars in damage and management expenses. Not every introduced species has such drastic effects, but invasives can be tough to eliminate.
While researchers try to get a handle on the impact of farm escapes, farmers are working to better contain the fish and reduce the ecological impact of the runaways. Some countries have tightened their aquaculture regulations. Researchers are proposing strategies ranging from new farm designs to altering fish genetics. As aquaculture becomes a widespread means to feed the planet’s protein-hungry people, the ecological effects are getting more attention.
If escapees weaken native wildlife, “we’re solving a food issue globally and creating another problem,” says population geneticist Kevin Glover of Norway’s Institute of Marine Research in Bergen. Norway, a top producer of marine fish, has done much of the research on farm escapes.

Not born to be wild
Fish farming is big business. In 2014, the industry churned out 73.8 million metric tons of aquatic animals worth about $160 billion, according to a report in July from the Food and Agriculture Organization of the United Nations in Rome.

Nearly two-thirds of this food comes from inland freshwater farms such as ponds, used in Asia for thousands of years. The rest is grown on marine and coastal farms, where farmed fish live in brackish ponds, lagoons or cages in the ocean.
Freshwater fish can escape from pond farms during events such as floods. Some escapees, such as tilapia, have hurt native species by competing with and eating wild fish. But sea farming has its own set of problems. The physical environment is harsh and cages are exposed to damaging ocean waves and wind, plus boats and predator attacks.

Salmon is one of the most heavily farmed marine fish. In some areas, the number of farmed salmon dwarfs wild populations. Norway’s marine farms hold about 380 million Atlantic salmon, while the country’s rivers are home to only about 500,000 wild spawning Atlantic salmon.

In the four decades that farmers have been cultivating Atlantic salmon, farmed strains have diverged from their wild cousins. When both are raised in standard hatchery conditions, farm-raised salmon can grow about three to five times heavier than wild salmon in the first year of life.

Salmon raised in farms also tend to be less careful; for instance, after being exposed to an artificial predator, they emerge more quickly from hiding places than wild fish. This risky behavior may have arisen partly because the fish haven’t faced the harsh challenges of nature. “The whole idea of a hatchery is that everything gets to survive,” says Philip McGinnity, a molecular ecologist at University College Cork in Ireland. Farmed fish don’t know better.
These differences are bad news for hybrid offspring and wild fish. In early experiments, hybrid offspring of farmed and wild salmon tended to fare poorly in the wild. In the 1990s, McGinnity’s team measured these fish’s “lifetime success” in spawning rivers and the ocean. Compared with wild salmon, hybrid offspring had a lifetime success rate about a fourth to a half as high. Around the same time, a team in Norway found that when wild fish swam with farmed fish in their midst, the number of wild offspring that survived long enough to leave the river to head to the ocean was about one-third lower than expected, perhaps because the fast-growing farmed offspring gobbled a lot of food or claimed territory.

“There was truly reason to be concerned,” says Ian Fleming, an evolutionary ecologist at Memorial University of Newfoundland in St. John’s, Canada, who was part of the Norway team.

Recent work supports the idea that farmed fish could crowd out wild fish by hogging territory in a river. In a study published last year in the Journal of Fish Biology, researchers found that the survival rate of young wild salmon dropped from 74 to 53 percent when the fish were raised in the same confined stream channels as young farmed salmon rather than on their own. When the channels had an exit, more wild fish departed the stream when raised with farmed salmon than when raised alone.

“These are fish that give up the territory and have to leave,” says study coauthor Kjetil Hindar, a salmon biologist at the Norwegian Institute for Nature Research in Trondheim.

A weaker mix
To find out how much escaped fish had genetically mingled with wild fish, Glover’s team obtained historical samples of salmon scales collected from 20 rivers in Norway before aquaculture became common. The researchers compared the DNA in the scales with that of wild salmon caught from 2001 to 2010 in those rivers.

Wild salmon in five of the 20 rivers had become more genetically similar to farmed fish over about one to four decades, the team reported in 2013 in BMC Genetics. In the most affected population, 47 percent of the wild fish’s genome originated from farmed strains. “We’re talking about more or less a complete swamping of the natural gene pool,” Glover says. Imagine buckets of paint — red, blue, green — representing each river, he says, and pouring gray paint into each one.

Interbreeding was less of an issue where wild fish were plentiful. The farmed fish aren’t good at spawning, so they won’t mate much if a lot of wild competitors are present. But in sparse populations, the farm-raised salmon may be able to “muscle in,” Glover says.
A larger study by Hindar’s team, published in July in the ICES Journal of Marine Science, showed that genetic mixing between wild and farmed salmon is happening on a large scale in Norway. Among 109 wild salmon populations, about half had significant amounts of genetic material from farmed strains that had escaped. In 27 populations, more than 10 percent of the fish’s DNA came from farmed fish.

What does that mean for the offspring? Each salmon population has adapted to survive in its habitat — a certain river, at a specific temperature range or acidity level. When farmed fish mate with wild fish, the resulting offspring may not be as well-suited to live in that environment. Over generations, as the wild population becomes more similar to farmed salmon, scientists worry that the fish’s survival could drop.

Scientists at several institutions in Norway are exploring whether genetic mixing changes the wild salmon’s survival rates, growth and other traits. Making a definitive link will be difficult. Other threats such as climate change and pollution also are putting stress on the fish.

If escapes can be stopped, wild salmon may rebound. Natural selection will weed out the weakest fish and leave the strongest, fish that got a lucky combination of hardy traits from their parents. But Glover worries that, just as a beach can’t recover if oil is spilled every year, the wild population can’t rally if farmed fish are continually pumped in: “Mother Nature cannot clean up if you constantly pollute.”

Uncertain consequences
In places where the species being farmed is not naturally abundant, researchers are taking a look at whether escapes could upset native ecosystems. For instance, European sea bass sometimes slip away from farms in the Canary Islands, where (except for a few small populations on the eastern end) the species doesn’t normally live.

In February 2010, storms battered cages at the island of La Palma, “like a giant tore up all the nets,” says Kilian Toledo-Guedes, a marine ecologist at the University of Alicante in Spain. About 1.5 million fish — mostly sea bass — reportedly swam free.

A couple of weeks later, the number of sea bass in nearby waters was “astounding,” he says. “I couldn’t see the bottom.” Sea bass density in waters near the farm was 162 times higher than it had been at the same time the previous year, his team reported in 2014 in Fisheries Management and Ecology. Fisheries data showing a spike in catches of sea bass by local fishermen that January also suggested that large unreported escapes had occurred before the storm.

Despite being raised in captivity, where they are fed pellets, some of the farmed fish learn to hunt. The researchers found that escaped sea bass caught four months after the 2010 farm breakdown had eaten mostly crabs. Sea bass from earlier escapes that had been living in the wild for several years had eaten plenty of fish as well. The results, reported in 2014 in Marine Environmental Research, suggest that escapees start by catching easy targets such as crustaceans and then learn to nab faster-moving fish.

So far, though, scientists have not seen clear signs that the escapees damaged the ecosystem. The density of sea bass around La Palma had fallen drastically by October 2010 and continued to decline the next year, probably because some fish couldn’t find enough to eat, while others were caught by fishermen or predators, according to a 2015 study by another team in the Journal of Aquaculture Research & Development.

Catches of small fish that sea bass eat, such as parrot fish, did not drop significantly after the 2010 escape or after a similar large escape in 1999, says study coauthor Ricardo Haroun, a marine conservation researcher at the University of Las Palmas de Gran Canaria in Spain. While he agrees that the industry should try to prevent escapes, he sees no evidence that the runaways are suppressing wild species.
If the escaped fish can breed and multiply, the risk of harming native species rises. In a study published in Marine Ecology in 2012, Toledo-Guedes and colleagues reported finding sexually mature sea bass around the central island of Tenerife. But Haroun says the water is too warm and salty for the fish to reproduce, and his team did not see any juveniles during their surveys of La Palma, nor have they heard any reports of juveniles in the area. Toledo-Guedes says that more extensive studies, such as efforts to catch larvae, are needed before reproduction can be ruled out.

Similarly, researchers can’t predict the consequences of the cobia escape in Ecuador. The water is the right temperature for reproduction, and these predators eat everything from crabs to squid. Castellanos-Galindo believes that farming cobia in the area is a mistake because escapes will probably continue, and the fish may eventually form a stable population in the wild that could have unpredictable effects on native prey and other parts of the ecosystem. He points to invasive lionfish as a cautionary tale: These predators, probably released from personal aquariums in Florida, have exploded across the Caribbean, Gulf of Mexico and western Atlantic and are devouring small reef fish.

The situation for cobia may be different. Local sharks and other predators will probably eat the escapees, whereas lionfish have few natural predators in their new territory, argues Diego Ardila, production manager at Ocean Farm. Milton Love, a marine fish ecologist at the University of California, Santa Barbara, also notes that lionfish settle in one small area, but cobia keep moving, so prey populations might recover after the cobia have moved on.

Not all introduced species become established or invasive, and it can take decades for the effects to become apparent. “Time will tell what happens,” says Andrew Sellers, a marine ecologist at the Smithsonian Tropical Research Institute in Panama City. “Basically, it’s just up to the fish.”

A slippery problem
Once fish have fled, farmers sometimes enlist fishermen to help capture the escapees. Professional fishermen caught nearly one-quarter of the sea bass and sea bream that escaped after the Canary Islands breach. On average, though, only 8 percent of fish are recaptured after an escape, according to a study published in June in Reviews in Aquaculture. Given the recapture failures, farmers and policy makers should focus on preventing escapes and maintaining no-fishing zones around farms to create a “wall of mouths,” local predators that can eat runaway fish, says coauthor Tim Dempster, a sustainable aquaculture researcher at the University of Melbourne in Australia.

Technical improvements could help. The Norwegian government rolled out a marine aquaculture standard in 2004 that required improvements, such as engineering nets, moorings and other equipment to withstand unusually strong storms. Compared with the period 2001–2006, the average number of Atlantic salmon escaping annually from 2007–2009 dropped by more than half. Ocean Farm in Ecuador has tightened security, increased cage inspections and switched to stronger net materials; no cobia have escaped since last year’s break-in, says Samir Kuri, the company’s operations manager.
Some companies raise fish in contained tanks on land to avoid polluting marine waters, reduce exposure to diseases and control growth conditions. But the industry is largely reluctant to adopt this option until costs come down. The money saved from reducing escapes probably wouldn’t make up for the current start-up expense of moving to land. The 242 escape events analyzed in the 2015 Aquaculture study cost farmers about $160 million. By one estimate, establishing a land-based closed-containment farm producing about 4,000 metric tons of salmon annually — a small haul by industry standards — would cost $54 million; setting up a similar-sized sea-cage farm costs $30 million.

Another solution is to raise fish that have three sets of chromosomes. These triploid fish, produced by subjecting fertilized eggs to a pressure shock, can’t reproduce and therefore wouldn’t proliferate or pollute the wild gene pool.

“The only ultimate solution is sterility,” Norway’s Glover says. “Accidents happen.” Escaped triploid salmon are less likely to disrupt mating by distracting females from wild males, the researchers wrote in Biological Invasions in May. But triploid fish don’t grow as well when the water is warmer than about 15° Celsius, and consumers might be reluctant to accept these altered salmon.

Although the ecological effects of fish farm escapes may take a long time to play out, most researchers agree that we shouldn’t take chances with the health of the oceans, which already face threats such as climate change, pollution and overfishing. With the aquaculture industry expanding at about 6 percent per year, farmers will have to keep improving their practices if they are to stay ahead of the runaway fish.

A summertime cold snap can, quite literally, take the bloom off the rose. Not so for Scotch heather — and now scientists know why.

Thick cell walls and narrow plumbing in the alpine shrub’s stems stop deadly ice crystals from spreading to its fragile flowers during sudden summer freezes, researchers report September 15 in PLOS ONE. That lets the flowers survive and the plant make seeds even if temperatures dip below freezing.

Once ice crystals start to form inside of a plant, they can spread very quickly, says Gilbert Neuner, a botanist at the University of Innsbruck in Austria who led the study. Those sharp crystals can destroy plant cells — and flowers are particularly sensitive. So plants living in cold climes have developed strategies to confine ice damage to less harmful spots.
Neuner and his team used infrared imaging to measure heat given off by Scotch heather (Calluna vulgaris) plants as they freeze. That technique revealed where and when ice was forming. And looking at thin slices of the plant under a microscope let the scientists pick apart the structure of the plant’s ice barrier.
Cells at the base of the flower stalks had thicker walls and were packed more closely together than elsewhere in the plant, the team found. In the same area, the pipelines that carry water up the plant — called xylem — were narrower and had fewer points where ice could potentially sneak through. Those modifications let the plants “supercool” their flowers. That is, even when the flowers chilled to below zero degrees Celsius, they contained liquid water instead of ice. Ice didn’t form in the Scotch heather flowers until far below normal freezing temperatures, ‒22° C, and ice that formed elsewhere in the plant didn’t spread to the flowers.
Other species sometimes put up temporary ice blockades, for instance to protect overwintering buds. But that usually cuts off the flow of water through the xylem — fine if a plant is dormant over the winter, but flowers facing a sudden summer freeze need a continuous supply of water. Scotch heather gets around this problem by threading its xylem right through the icy barrier.

Membranes let water pass between the xylem cells, and these membranes might ultimately control the spread of ice crystals in C. vulgaris, Neuner suspects. Tiny pores in the membranes are too small to let ice crystals through the barrier. And when water molecules are found inside such small holes, the molecules are bound so tightly to the structures around them that they behave more like a gel instead of crystalizing into ice. The team hopes to test the idea in future studies.
Other flowering alpine plants could use a similar strategy. “I don’t think that this is unique to this plant,” says Sanna Sevanto, a tree physiologist at Los Alamos National Laboratory in New Mexico who wasn’t involved in the study. “It’s just that nobody has looked at it.”

Concussions, particularly those among children playing sports, are on parents’ minds. The fervor over NFL players’ brains and those of other elite athletes has trickled all the way down to mini-kicker soccer teams and peewee football leagues. And parents are right to be worried. Concussions seem to be on the rise. From 1990 to 2014, the rate of concussions in youth soccer players jumped by over 1,000 percent, a recent study estimated.

This increase might be driven in part by more inclusive definitions of concussion, a common form of traumatic brain injury that can come with headaches, confusion and memory trouble. More awareness might also drive numbers up; because parents, coaches and referees are more alert to the possibility of a concussion, more kids might be getting the diagnosis. But games may have become more competitive, too, leading to more body clashes that jolt the brain.

When a kid gets concussed, the instinct of many parents, myself included, is to cocoon their child, limiting social interaction, activity and even sleep, a recent poll conducted by researchers at UCLA suggests. The survey asked about 500 parents about how they would handle a child who had symptoms a week after a concussion. Eighty-four percent of the respondents said they would restrict their child’s physical activity for the week after the injury, 62 percent said they would take away their child’s electronics and 77 percent said they’d even wake their child up during the night. But those measures “can certainly be unhelpful,” says pediatric neurologist Christopher Giza of UCLA. “There’s some evidence it may be harmful.”

Giza points out that each child is unique, and the recovery process ought to be tailored by his or her medical team to best help the individual. But in general, excessive rest and isolation might work against kids. Last year, scientists found that children and teenagers who strictly rested for five days reported more symptoms than those who rested for one to two days. What’s more, recovery took longer for the kids who got the five-day break.

Complete isolation and rest may cause children to grow anxious and despondent, Giza says. With their normal routines interrupted, they may focus more on their symptoms. Social interactions, even those that come via a screen, may help kids feel better sooner. Gentle exercise, such as walks and swimming, is also a good thing. And despite what parents may have heard, children with concussions need sleep to recover. “Waking the kid up every few hours only worsens symptoms,” Giza says. It’s not surprising that a week of poor sleep can dial up fatigue, irritability and slow thinking.

There is one very important limit that should still be respected for kids recovering from concussions: No more head knocks. Concussions in quick succession can be extra pernicious for the brain. That means kids shouldn’t return to any sport that puts them at risk for a second concussion until they are fully recovered. In a concussion’s aftermath, reflexes are blunted, balance may be off and thinking may be slow, Giza says. Those deficits put children at more risk for getting hit.

Some sports leagues have begun changing their rules to make the game safer. This season, 5- to 10-year-olds playing in a Pop Warner football game, for instance, will no longer have kickoffs, a game-starting play responsible for an inordinate amount of concussions. Game tweaks like that, along with more vigilant coaches and parents, will help protect these little brains.

You don’t need a degree in science to monitor backyard owls or measure trees. And anyone with a computer can help scientists track seal populations in Antarctica. Citizen science projects like these — which depend on crowdsourced data — are booming. And when faced with a planet scarred by industrialization and climate change, these efforts might be exactly what we need, environmental journalist Mary Ellen Hannibal argues in Citizen Scientist.
What we call “citizen science” was once just “science.” After all, many early conservationists and natural historians — people like John Muir — weren’t academics. As species disappear faster and faster, scientists can’t work alone. They need the eyes and ears of passionate people who are watching as flowers bloom earlier each year and butterflies become sparser.

Hannibal dips her toes into some of the citizen science projects happening within driving distance of her home in San Francisco. She chronicles efforts to count, track and save a variety of species, including sea otters and redwood trees.

Along the way, Hannibal discovers heroes both modern and historical: For instance, Rebecca Moore, who leads Google Earth Outreach, originally developed the mapping tool in the early 2000s to help stop logging in the Santa Cruz Mountains. And Alice Eastwood, botany curator at the California Academy of Sciences in the early 1900s, helped build the museum’s plant collection. Lacking a college degree, she collected specimens for nearly 60 years — and even saved part of the collection from the 1906 San Francisco earthquake.

While Hannibal is contemplating extinction and habitat destruction, her father is dying from cancer. Her field expeditions become a lens through which she processes her dad’s death. The parallels make Citizen Scientist part memoir, part science tale and part history book. Hannibal has a conversational writing style that moves quickly from topic to topic, punctuated with humorous and thoughtful asides.

Although centered in California, the book has a global message: Humans have much in common with the species we’re trying to save. Grizzlies and wolves, for instance, “leave their natal home, light out for a huge territory, find a mate, and establish a new base of operations,” Hannibal writes. The human heroes in our storybooks aren’t so different.

A genetic study of HIV viruses from the 1970s may finally clear the name of a man long identified as the source of the AIDS epidemic in the United States. HIV came to New York City between 1969 and 1973, long before the man known as Patient Zero became infected, researchers report October 26 in Nature.

Using techniques developed to decipher badly degraded ancient DNA from fossils, researchers reconstructed the genetic instruction books of eight HIV viruses from blood samples collected in 1978 and 1979 in New York City and San Francisco. The viral DNA was so genetically diverse that the viruses must have been circulating in the cities for years, picking up variations, says evolutionary biologist Michael Worobey of the University of Arizona in Tucson.
Worobey and colleagues calculate that the virus probably first jumped to the United States in 1970 or 1971. So HIV spread for about a decade before AIDS was recognized in 1981 and found to be caused by a retrovirus in 1983.
Examining the relationships between the New York City and San Francisco viruses with HIV strains from elsewhere let researchers trace the virus’s path. The eight American samples all came from the same branch of the HIV family tree as ones from the Caribbean. That suggests that HIV spread from Africa to the Caribbean before making its way to the United States. New York HIV samples were more diverse than those from California, indicating that New York City was probably the hub of early HIV spread and the virus arrived in San Francisco later.
Worobey and colleagues also examined HIV DNA from Patient Zero. Also known as Case 57, he was part a 1984 study of gay men with AIDS in Los Angeles who had either a rare cancer called Kaposi’s sarcoma or Pneumocystis carinii pneumonia, both complications of the disease. Researchers from the Centers for Disease Control and Prevention found that many of the men had had sexual contact with each other, helping to establish that HIV is sexually transmitted.
Later, in the book And the Band Played On, author Randy Shilts identified Patient Zero as an Air Canada flight attendant named Gaëtan Dugas. It was widely interpreted that Dugas was the first case of HIV in the United States, even though the CDC never claimed — and has repeatedly refuted — that, says epidemiologist James Curran, a coauthor of the 1984 study who is now at Emory University in Atlanta. Part of the confusion may have been that Patient Zero was supposed to be identified as Patient O (for “outside of California”).

Dugas became a flight attendant in 1974 and began traveling to the United States shortly after, says Richard McKay, coauthor of the new study and a medical historian at the University of Cambridge. Dugas estimated that he had about 250 male sexual partners each year between 1979 and 1981. Shilts and others contended that Dugas was intentionally spreading the virus to others, though he was diagnosed with Kaposi’s sarcoma in 1980 before anyone knew what AIDS was or that it was caused by a virus.

Now, the genetic analysis confirms that Dugas was not carrying the earliest version of the virus. “This individual was simply one of thousands infected before HIV/AIDS was recognized,” McKay says.

The new study is a cautionary tale against trying to pin the spread of an infectious disease on any one person, says Robert Remien, a behavioral scientist at Columbia University Medical Center. “There’s no blame or cause to be laid on any of those people in those early years.”

Editor’s note: This story was updated November 10, 2016, to fix the alignment of the timeline with the phylogenetic tree and to update the number of sequential diagnoses in the Patient Zero cluster of AIDS cases.

Many preschoolers take a surprisingly long and bumpy mental path to the realization that people can have mistaken beliefs — say, thinking that a ball is in a basket when it has secretly been moved to a toy box. Traditional learning curves, in which kids gradually move from knowing nothing to complete understanding, don’t apply to this landmark social achievement and probably to many other types of learning, a new study concludes.

Kids ranging in age from 3 to 5 often go back and forth between passing and failing false-belief tests for several months to more than one year, say psychologist Sara Baker of the University of Cambridge and her colleagues. A small minority of youngsters jump quickly from always failing to always passing these tests, the scientists report October 20 in Cognitive Psychology.
“If these results are replicated, it will surprise a lot of researchers that there is such a low level of sudden insight into false beliefs,” says psychologist Malinda Carpenter, currently at the Max Planck Institute for Evolutionary Anthropology in Leipzig. Early childhood researchers generally assume that preschoolers either pass or fail false-belief tests, with a brief transition between the two, explains Carpenter, who did not participate in the new study. Grasping that others sometimes have mistaken beliefs is a key step in social thinking.

False-belief understanding may start out as something that can be indicated nonverbally but not described. Human 2-year-olds and even chimpanzees tend to look toward spots where a person would expect to find a hidden item that only the children or apes have seen moved elsewhere (SN Online: 10/6/16).

Numerous investigations suggest that neurologically healthy kids between ages 3 and 5 consciously appreciate when others have formed mistaken beliefs. But those studies report average scores on false-belief tests for groups of preschoolers. That leaves unexamined how individual kids progress — or not — as mind readers.

Baker’s team generated individual scoring profiles for 52 children repeatedly assessed for false-belief understanding between ages 3 and 5. Trials occurred over roughly one to two years. Two types of false-belief tasks were alternately presented about every two to six weeks, either at a preschool, in a lab or at a child’s home.

In one task, an experimenter used pictures to help describe a situation in which someone moves an object from one location to another once a friend leaves — say, taking a ball from a basket and putting it in a toy box. Children were asked where the friend would later look for the object.
In a second task, children observed a container’s unexpected contents, such as a sock in a crayon box or a toy cow in an egg carton. Kids reported what they originally thought was inside the container and what another person would think is inside it.

Nine children, including some of the youngest ones, passed their first three trials. All except one of the nine continued to pass trials at a high rate. The remaining 43 children failed at least one of the first three trials. A statistical analysis calculated the likelihood that a series of scores for a particular child reflected gains, losses or no change in false-belief understanding.

Five of the 43 children achieved rapid insights into false beliefs, consistently passing trials immediately after a string of failed trials. Another 22 youngsters showed different patterns of improvement, such as going from a 12 percent likelihood of passing trials to a 50 percent chance by the study’s end. None of them moved gradually and steadily from failing to passing false belief tests. Smooth learning curves are statistical illusions created by averaging group scores, the researchers suspect.

Four kids started out failing false-belief tests and showed no signs of improvement over time. Another 10 children sometimes passed and sometimes failed throughout the study. Statistical profiles were inconclusive for two children.

Related findings, although based on group statistics, nonetheless suggest that grade-schoolers shift among various problem-solving strategies when learning mathematical concepts (SN: 3/17/01, p. 172). Baker’s statistical method could enhance the study of how individual children develop math skills and other forms of reasoning, says psychologist Rose Scott of the University of California, Merced.