Lightning seen as cause of puzzling chondrules — Lightning flashes in the huge cloud of primeval dust and gas from which the planets in the solar system condensed may have caused formation of the puzzling objects known as chondrules … the tiny, rounded granules about the size of poppy seeds found in stony meteorites…. Dry lightning flashes could have been the source of the fast heating that, followed by quick cooling, [explains] the glassy structure of chondrules. — Science News, July 16, 1966
Update Chondrules are among the oldest pieces of planetary building blocks, formed roughly 4.6 billion years ago during the solar system’s first few million years. How they formed is still up for debate. But the lightning hypothesis has mostly fallen out of favor. One leading idea is that chondrules emerged in the wake of shock waves that rippled through the planet nursery. Those shock waves may have been triggered by collisions of embryonic planets, gas waves spiraling around the sun or strong solar flares.
When Tommy the chimpanzee first came to London’s zoo in the fall of 1835, he was dressed in an old white shirt.
Keepers gave him a new frock and a sailor hat and set him up in a cozy spot in the kitchen to weather the winter. Visitors flocked to get a look at the little ape roaming around the keepers’ lodge, curled up in the cook’s lap or tugging on her skirt like a toddler. Tommy was a hit — the zoo’s latest star. Six months later, he was dead.
Tommy’s sorrowful story comes near the middle of Isobel Charman’s latest book, The Zoo, a tale of the founding of the Gardens of the Zoological Society of London, known today as the London Zoo. The book lays out a grand saga of human ambition and audacity, but it’s the animals’ stories — their lives and deaths and hardships — that catch hold of readers and don’t let go.
Charman, a writer and documentary producer, resurrects almost three decades of history, beginning in 1824, when the zoo was still just a fantastical idea: a public menagerie of animals “that would allow naturalists to observe the creatures scientifically.”
It was a long, hard path to that lofty dream, though: In the zoo’s early years, exotic creatures were nearly impossible to keep alive. Charman unloads a numbing litany of animal misery that batters the reader like a boxer working over a speed bag. Kangaroos hurl themselves at fences, monkeys attack each other in cramped, dark cages and an elephant named Jack breaks a tusk while smashing up his den. Charman’s parade of horrors boggles the mind, as does the sheer number of animals carted from all corners of the world to the cold, wet enclosures of the zoo.
Her story is an incredible piece of detective work, told through the eyes of many key players and famous figures, including Charles Darwin. Charman plumbs details from newspaper articles, diaries, census records and weather reports to craft a narrative of the time. She portrays a London that’s gritty, grimy and cold, where some aspects of science and medicine seem stuck in the Dark Ages. Doctors still used leeches to bleed patients, and no one had a clue how to care for zoo animals. Zoo workers certainly tried — applying liniment to sores on a lion’s legs, prescribing opium for a sick puma and treating a constipated llama with purgatives. But nothing seemed to stop the endless conveyor belt that brought living animals in and carried dead ones out. Back then, caring for zoo animals was mostly a matter of trial and error, Charman writes. What seems laughably obvious now — animals need shelter in winter, cakes and buns aren’t proper food for elephants — took zookeepers years to figure out.
Over time the zoo adapted, making gradual changes that eventually improved the lives of its inhabitants. It seemed to morph, finally, from mostly “a playground of the privileged,” as Charman calls it, to a reliable place for scientific study, where curious people could learn about the “wild and wonderful” creatures within.
One of those people was Darwin, whose ideas about human origins clicked into place after he spent time with Jenny the orangutan. Her teasing relationship with her keeper, apparent understanding of language and utter likeness to people helped convince Darwin that humankind was just another branch on the tree of life, Charman writes. Darwin’s work on the subject wouldn’t be published for decades, but in the meantime, the zoo’s early improvements seemed to have stuck. Over 30 years after Tommy the chimpanzee died in his keeper’s arms, a hippopotamus gave birth to “the first captive-bred hippo to be reared by its mother,” Charman notes. The baby hippo not only survived — she lived for 36 years.
Readers may wonder how standards for animal treatment have changed over time. But Charman sticks to history, rather than examining contrasts to modern zoos. Still, what she offers is gripping enough on its own: a bold, no-holds-barred look at one zoo’s beginning. It was impressive, no doubt. But it wasn’t pretty.
Researchers have identified new enemies in the war on cancer: ones that are already inside cells and that no one can avoid.
Random mistakes made as stem cells divide are responsible for about two-thirds of the mutations in cancer cells, researchers from Johns Hopkins University report in the March 24 Science. Across all cancer types, environment and lifestyle factors, such as smoking and obesity, contribute 29 percent of cancer mutations, and 5 percent are inherited. That finding challenges the common wisdom that cancer is the product of heredity and the environment. “There’s a third cause and this cause of mutations is a major cause,” says cancer geneticist Bert Vogelstein.
Such random mutations build up over time and help explain why cancer strikes older people more often. Knowing that the enemy will strike from within even when people protect themselves against external threats indicates that early cancer detection and treatment deserve greater attention than they have previously gotten, Vogelstein says.
Vogelstein and biomathematician Cristian Tomasetti proposed in 2015 that random mutations are the reason some organs are more prone to cancer than others. For instance, stem cells are constantly renewing the intestinal lining of the colon, which develops tumors more often than the brain, where cell division is uncommon. That report was controversial because it was interpreted as saying that most cancers are the result of “bad luck.” The analysis didn’t include breast and prostate cancers. Factoring in those common cancers might change the results, some scientists said. And because the researchers looked at only cancer within the United States, critics charged that the finding might not hold up when considering places around the world where different environmental factors, such as infections, affect cancer development.
In the new study, Vogelstein, Tomasetti and Hopkins colleague Lu Li examined data from 69 countries about 17 types of cancer, this time including breast and prostate. Again, the researchers found a strong link between cancer and tissues with lots of dividing stem cells. The team also used DNA data and epidemiological studies to calculate the proportions of mutations in cancer cells caused by heredity or environmental and lifestyle factors. Remaining mutations were attributed to random errors — including typos, insertions or deletions of genes, epigenetic changes (alterations of chemical tags on DNA or proteins that affect gene activity) and gene rearrangements. Such errors unavoidably happen when cells divide. Usually cancer results after a cell accumulates many mutations. Some people will have accumulated a variety of cancer-associated mutations but won’t get cancer until some final insult goads the cell into becoming malignant (SN: 12/26/15, p. 28). For some tumors, all the mutations may be the hit-and-miss result of cell division mistakes. There’s no way to evade those cancers, Vogelstein says. Other malignancies may spring up as a result of different combinations of heritable, environmental and random mutations. Lung cancer and other tumor types that are strongly associated with environmentally caused mutations could be eluded by avoiding the carcinogen, even when most of the mutations that spur cancer growth arise from random mistakes, Tomasetti says.
“They are venturing into new territory,” says Giovanni Parmigiani, a biostatistician at the Harvard T.H. Chan School of Public Health. Tomasetti, Li and Vogelstein are the first to rigorously estimate the contribution of environment, heredity and DNA-copying errors to cancer, he says. “Perhaps the estimates will improve in the future, but theirs seems like a very solid starting point.”
Now that the Hopkins researchers have pointed it out, the relationship between dividing cells and cancer seems obvious, says biological physicist Bartlomiej Waclaw of the University of Edinburgh. “I don’t think that the existence of this correlation is surprising,” he says. “What’s surprising is that it’s not stronger.”
Some tissues develop cancers more or less often than other tissues with a similar number of cell divisions, Waclaw and Martin Nowak of Harvard University pointed out in a commentary on the Hopkins study, published in the same issue of Science. That suggests some organs are better at nipping cancer in the bud. Discovering how those tissues avoid cancer could lead to new ways to prevent tumors elsewhere in the body, Waclaw suggests.
Other researchers say the Hopkins team is guilty of faulty reasoning. “They are assuming that just because tissues which have high stem cell turnover also have high cancer rates, that one is causing the other,” says cancer researcher Anne McTiernan of the Fred Hutchinson Cancer Research Center in Seattle. “In this new paper, they’ve added data from other countries but haven’t gotten away from this biased thinking.”
Tomasetti and colleagues based their calculations on data from Cancer Research UK that suggest that 42 percent of cancers are preventable. Preventable cancers are ones for which people could avoid a risk factor, such as unprotected sun exposure or tanning bed use, or take positive steps to lower cancer risks, such as exercising regularly and eating fruits and vegetables. But those estimates may not be accurate, McTiernan says. “In reality, it’s very difficult to measure environmental exposures, so our estimates of preventability are likely very underestimated.”
To attribute so many cancer mutations to chance seems to negate public health messages, Waclaw says, and some people may find the calculation that 66 percent of cancer-associated mutations are unavoidable disturbing because they spend a lot of time trying to prevent cancer. “It’s important to consider the randomness, or bad luck, that comes with cellular division,” he says.
In fact, Tomasetti and Vogelstein stress that their findings are compatible with cancer-prevention recommendations. Avoiding smoking, tanning beds, obesity and other known carcinogens can prevent the “environmental” mutations that combine with inherited and random mutations to tip cells into cancer. Without those final straws loaded from environmental exposures, tumors may be averted or greatly delayed.
People with cancer may be able to take some comfort from the study, says Elaine Mardis, a cancer genomicist at the Nationwide Children’s Hospital in Columbus, Ohio. “Perhaps the positive message here is that, other than known risk factors, such as smoking, radiation exposure and obesity, there is a component of cancer that is simply a consequence of being human.”
The way babies learn to speak is nothing short of breathtaking. Their brains are learning the differences between sounds, rehearsing mouth movements and mastering vocabulary by putting words into meaningful context. It’s a lot to fit in between naps and diaper changes.
A recent study shows just how durable this early language learning is. Dutch-speaking adults who were adopted from South Korea as preverbal babies held on to latent Korean language skills, researchers report online January 18 in Royal Society Open Science. In the first months of their lives, these people had already laid down the foundation for speaking Korean — a foundation that persisted for decades undetected, only revealing itself later in careful laboratory tests.
Researchers tested how well people could learn to identify and speak tricky Korean sounds. “For Korean listeners, these sounds are easy to distinguish, but for second-language learners they are very difficult to master,” says study coauthor Mirjam Broersma, a psycholinguist of Radboud University in Nijmegen, Netherlands. For instance, a native Dutch speaker would listen to three distinct Korean sounds and hear only the same “t” sound.
Broersma and her colleagues compared the language-absorbing skills of a group of 29 native Dutch speakers to 29 South Korea-born Dutch speakers. Half of the adoptees moved to the Netherlands when they were older than 17 months — ages at which the kids had probably begun talking. The other half were adopted as preverbal babies younger than 6 months. As a group, the South Korea-born adults outperformed the native-born Dutch adults, more easily learning both to recognize and speak the Korean sounds.
This advantage held when the researchers looked at only adults who had been adopted before turning 6 months old. “Even those who were only 3 to 5 months old at the time of adoption already knew a lot about the sounds of their birth language, enough even to help them relearn those sounds decades later,” Broersma says.
Uncovering this latent skill decades after it had been imprinted in babies younger than 6 months was thrilling, Broersma says. Many researchers had assumed that infants start to learn the sounds of their first language later, around 6 to 8 months after birth. “Our results show that that assumption must have been wrong,” she says.
It’s possible that some of these language skills were acquired during pregnancy, as other studies have hinted. Because the current study didn’t include babies who were adopted immediately after birth, the results can’t say whether language heard during gestation would have had an influence on later language skills. Still, the results suggest that babies start picking up language as soon as they possibly can.
When escaping from humans, narwhals don’t just freeze or flee. They do both.
These deep-diving marine mammals have similar physiological responses to those of an animal frozen in fear: Their heart rate, breathing and metabolism slow, mimicking a “deer in the headlights” reaction. But narwhals (Monodon monoceros) take this freeze response to extremes. The animals decrease their heart rate to as slow as three beats per minute for more than 10 minutes, while pumping their tails as much as 25 strokes per minute during an escape dive, an international team of researchers reports in the Dec. 8 Science. “That was astounding to us because there are other marine mammals that can have heart rates that low but not typically for that long a period of time, and especially not while they’re swimming as hard as they can,” says Terrie Williams, a biologist at the University of California, Santa Cruz. So far, this costly escape has been observed only after a prolonged interaction with humans.
Usually, narwhals will escape natural predators such as killer whales by stealthily slipping under ice sheets or huddling in spots too shallow for their pursuers, Williams says. But interactions with humans — something that will happen increasingly as melting sea ice opens up the Arctic — may be changing that calculus. “When narwhals detect humans, they often dive quickly and disappear from sight,” says Kristin Laidre, an ecologist at the University of Washington in Seattle who studies marine mammals in the Arctic. Williams and her colleagues partnered with indigenous hunters in East Greenland to capture narwhals in nets. Then, the researchers stuck monitoring equipment to the narwhals’ backs with suction cups and released the creatures. The team tracked the tail stroke rate and cardiovascular response of the narwhals after their release, and determined how much energy the animals used during their deep escape dives.
During normal dives, narwhals reduce their heart rate to about 10 to 20 beats per minute to conserve oxygen while spending prolonged time underwater. These regular deep dives to forage for food don’t require rigorous exercise. But during escape dives after being entangled in a net for an hour or longer, “the heart rates were going down to levels of three and four beats per minute, and being maintained at that level for 10 minutes at a time,” Williams says.
The narwhals were observed making multiple dives to depths of 45 to 473 meters in the hours following escape. When fleeing, the tusked animals expended about three to six times as much energy as they normally burn while resting. The authors calculated that the frantic getaway, combined with what they called “cardiac freeze,” severely and rapidly depletes the narwhals’ available oxygen in their lungs, blood and muscles — using 97 percent of the creatures’ oxygen stores compared with 52 percent on normal dives of similar depth and duration.
“There is a concern from our group that this is just pushing the biology of these animals beyond what they can do,” Williams says. As human activity increases in the Arctic, there may be more chance of inciting this potentially harmful escape response in narwhals.
The creatures may also become more vulnerable to other human-caused disturbances, such as seismic exploration, hunting and noise from large vessels and fishing boats. The researchers plan to investigate whether these activities cause the same flee-and-freeze reaction, and whether this extreme response affects narwhals’ long-term health.
This study “provides a new physiological angle on the vulnerability of narwhals to anthropogenic disturbance, which is likely to increase in the Arctic with sea ice loss,” Laidre says. Better understanding the human impacts on narwhals is essential for conservation of this species, she adds.
Discoveries of planets around distant stars have become almost routine. But finding seven exoplanets in one go is something special. In February, a team of planet seekers announced that a small, cool star some 39 light-years away, TRAPPIST-1, hosts the most Earth-sized exoplanets yet found in one place: seven roughly Earth-sized worlds, at least three of which might host liquid water (SN: 3/18/17, p. 6).
These worlds instantly became top priorities in the search for life outside the solar system. “TRAPPIST-1 is on everybody’s wish list,” says exoplanet astronomer Lisa Kaltenegger of Cornell University. But the planets and their dim star have also stoked a raging debate about what makes a planet habitable in the first place. Astrophysicist Michaël Gillon of the University of Liège in Belgium and colleagues found the family of worlds orbiting the ultracool dwarf star, dubbed TRAPPIST-1 for the small telescope in Chile used to discover its planets.
“I don’t think the cachet of that system is going away anytime soon,” says exoplanet expert Sara Seager of MIT.
The TRAPPIST telescope team first announced in May 2016 that the star had three temperate, rocky planets. Staring at the system with the Spitzer Space Telescope for almost three weeks straight revealed that the third planet was actually four more — all Earth-sized, and three of them are in the star’s habitable zone, the region where temperatures are right for liquid water on a planet’s surface. A seventh planet was caught crossing the star as well, though follow-up observations showed it is too cold for life as we know it (SN: 6/24/17, p. 18). Similar but different Planets orbiting the star TRAPPIST-1 are a lot alike in some ways and distinct in others. The slideshow below shows each planet’s specs, including how long it takes to orbit the dwarf star, distance from the star (in astronomical units), and radius and mass relative to Earth. The number of worlds alone makes the TRAPPIST-1 system a good spot to look for life. An alien observing our solar system would think Venus, Earth and Mars all fall in the habitable zone. But only one is inhabited. The fact that TRAPPIST-1 has so many options increases the odds that the system hosts life, Seager says.
As an ultracool dwarf, TRAPPIST-1 rides the edge of what counts as a star. Such stars burn through their nuclear fuel so slowly that they can live for many billions of years, which gives any life on their planets a long time to grow and evolve. This star’s habitable zone is also incredibly close in, offering astronomers many chances to observe the planets orbiting their star.
The three planets in the habitable zone cross in front of the star every 6.10, 9.21 and 12.35 days. If two or more turn out to be habitable, then they could share life among them, either by tossing meteorites back and forth or — in the case of spacefaring civilizations — by deliberate space travel. Future space-based observatories will be able to see starlight filtering through the planets’ atmospheres, if the planets have atmospheres. Gillon and colleagues are looking for signs of escaping hydrogen, a signal that an atmosphere might be there. “We’re already preparing,” he says.
But ultracool dwarfs are also ill-tempered. They tend to emit frequent, powerful stellar flares, which could rip away a planet’s atmosphere, threatening any potential for life. The planet-hunting Kepler space telescope recently watched TRAPPIST-1 for 80 days and saw it flare 42 times. One of those flares was as strong as Earth’s 1859 Carrington Event, among the strongest geomagnetic storms ever observed.
But there are other promising systems. Recently, a similar star, Ross 128, only 11 light-years from Earth and much calmer than TRAPPIST-1, was found to have an Earth-mass planet, making it a better place to look for life, researchers reported in November in Astronomy & Astrophysics.
Whether such stars are good or bad for life is an old and open question (SN: 6/24/17, p. 18). TRAPPIST-1’s advantage is in its numbers. “We can check it, not just with one planet but with many planets,” Kaltenegger says. “You have hotter than Earth, like Earth and colder than Earth. If you wanted Goldilocks, this is the ideal scenario.”
TRAPPIST-1 is just an opening act. A bigger, more sensitive observatory called SPECULOOS is expected to be fully operational in the Chilean desert in early 2019, Gillon says. SPECULOOS will seek planets around 1,000 ultracool dwarf stars over 10 years. “We are at the edge of maybe detecting life around another star,” he says. “It’s really a possibility.”
The holiday onslaught is upon us. For some families with children, the crush of holiday gifts — while wonderful and thoughtful in many ways — can become nearly unmanageable, cluttering both rooms and minds.
This year, I’m striving for simplicity as I pick a few key presents for my girls. I will probably fail. But it’s a good goal, and one that has some new science to back it. Toddlers play longer and more creatively with toys when there are fewer toys around, researchers report November 27 in Infant Behavior and Development. Researchers led by occupational therapist Alexia Metz at the University of Toledo in Ohio were curious about whether the number of toys would affect how the children played, including how many toys they played with and how long they spent with each toy. The researchers also wondered about children’s creativity, such as the ability to imagine a bucket as a drum or a hat.
In the experiment, 36 children ages 18 to 30 months visited a laboratory playroom twice while cameras caught how they played. On one visit, the room held four toys. On the other visit, the room held 16 toys.
When in the playroom with 16 toys, children played with more toys and spent less time with each one over a 15-minute session, the researchers found. When the same kids were in a room with four toys, they stuck with each toy longer, exploring other toys less over the 15 minutes.
What’s more, the quality of the children’s play seemed to be better when fewer toys were available. The researchers noted more creative uses of the toys when only four were present versus 16. Metz and colleagues noticed that initial attempts to play with a toy were often superficial and simple. But if a kid’s interest stuck, those early pokes and bangs turned into more sophisticated manners of playing. This type of sustained engagement might help children learn to focus their attention, a skill Metz likened to a “muscle that they have to exercise.” This attentional workout might not happen if kids are perpetually exposed to lots of distracting toys.
The toys used in the study didn’t include electronic devices such as tablets. Only one of the four toys and only four of the 16 toys used batteries. Noisy toys may have their own troubles. They can cut down on parent-child conversations, scientists have found. It’s possible that electronics such as televisions or tablets would have even greater allure than other toys.
Nor do the researchers know what would happen if the study had been done in kids’ houses and with their own toys. It’s possible that the novelty of the new place and the new toys influenced the toddlers’ behavior. (As everyone knows, the toys at a friend’s house are way better than the toys a kid has at home, even when they are literally the exact same toy.)
The results don’t pinpoint the optimal number of toys for optimal child development, Metz says. “It’s a little preliminary to say this is good and that is bad,” she says. But she points out that many kids are not in danger of having too few toys. In fact, the average number of toys the kids in the study had was 87. Five families didn’t even provide toy counts, instead answering “a lot.”
“Because of the sheer abundance of toys, there’s no harm in bringing out a few at a time,” Metz says.
That’s an idea that I’ve seen floating around, and I like it. I’ve already started packing some of my kids’ toys out of sight, with the idea to switch the selection every so often (or more likely, never). Another recommendation I’ve seen is to immediately hide away some of the new presents, which aren’t likely to be missed in the holiday pandemonium, and break them out months later when the kids need a thrill.
If more nerve cells mean more smarts, then dogs beat cats, paws down, a new study on carnivores shows. That harsh reality may shock some friends of felines, but scientists say the real surprises are inside the brains of less popular carnivores. Raccoon brains are packed with nerve cells, for instance, while brown bear brains are sorely lacking.
By comparing the numbers of nerve cells, or neurons, among eight species of carnivores (ferret, banded mongoose, raccoon, cat, dog, hyena, lion and brown bear), researchers now have a better understanding of how different-sized brains are built. This neural accounting, described in an upcoming Frontiers in Neuroanatomy paper, may ultimately help reveal how brain features relate to intelligence. For now, the multispecies tally raises more questions than it answers, says zoologist Sarah Benson-Amram of the University of Wyoming in Laramie. “It shows us that there’s a lot more out there that we need to study to really be able to understand the evolution of brain size and how it relates to cognition,” she says.
Neuroscientist Suzana Herculano-Houzel of Vanderbilt University in Nashville and colleagues gathered brains from the different species of carnivores. For each animal, the researchers whipped up batches of “brain soup,” tissue dissolved in a detergent. Using a molecule that attaches selectively to neurons in this slurry, researchers could count the number of neurons in each bit of brain real estate.
For most animals, the team found the expected numbers of neurons, given a certain brain size. Those expectations came in part from work on other mammals’ brains. That research showed that with the exception of primates (which pack in lots of neurons without growing bigger brains), there’s a predictable relationship between the size of the cerebral cortex — the wrinkly outer layer of the brain that’s involved in thinking, learning and remembering — and the number of neurons contained inside it.
Story continues below interactive graphic Feeling brainy Comparing brain size and number of nerve cells in the cerebral cortex among several animal species revealed some surprises. Golden retrievers, for example, have many more nerve cells than cats, and brown bears have an unexpectedly low number of nerve cells given the relatively large size of their brain. Raccoons have a surprising number of nerve cells considering their small noggin. It’s too early, however, to say how neuron number relates to animal intelligence.
Tap or click the graph below for more information.
But some of the larger carnivores with correspondingly larger cortices had surprisingly few neurons. In fact, a golden retriever — with 623 million neurons packed into its doggy cortex —topped both lions and bears, the team found. (For scale, humans have roughly 16.3 billion neurons in the cortex.)
The brown bear is especially lacking. Despite being about 10 times bigger than a cat’s cortex, the bear’s cortex contained roughly the same number of neurons, about 250 million. “It’s just flat out missing 80 percent of the neurons that you would expect,” Herculano-Houzel says. She suspects that there’s a limit to how much food a big predator can catch and eat, especially one that hibernates. That caloric limit might also cap the number of energetically expensive neurons.
Another exception — but in the opposite direction — was the raccoon, which has a cat-sized brain but a doglike neuron number, a finding that fits the nocturnal mammal’s reputation as a clever problem-solver. Benson-Amram cautions that it’s not clear how these neuron numbers relate to potential intelligence. Raccoons are very dexterous, she says, and it’s possible that a beefed-up brain region that handles touch, part of the cortex, could account for the neuron number.
Herculano-Houzel expected large predators such as lions to have lots of neurons. “We went into this study with the expectation that being a predator would require smarts,” she says. But in many cases, a predator didn’t seem to have more neurons than its prey. A lion, for instance, has about 545 million neurons in its cerebral cortex, while a blesbok antelope, which has a slightly smaller cortex, has about 571 million, the researchers previously found.
It’s too early to say how neuron number relates to animal intelligence. By counting neurons, “we’ve figured out one side of that equation,” Herculano-Houzel says. Those counts still need to be linked to animals’ thinking abilities.
Some studies, including one by Benson-Amram, have found correlations between brain size, neuron number and problem-solving skills across species. But finding ways to measure intelligence across different species is challenging, she says. “I find it to be a really fun puzzle, but it’s a big challenge to think, ‘Are we asking the right questions?’”
The hardy souls who manage to push shorts season into December might feel some kinship with the thirteen-lined ground squirrel.
The critter hibernates all winter, but even when awake, it’s less sensitive to cold than its nonhibernating relatives, a new study finds. That cold tolerance is linked to changes in a specific cold-sensing protein in the sensory nerve cells of the ground squirrels and another hibernator, the Syrian hamster, researchers report in the Dec. 19 Cell Reports. The altered protein may be an adaptation that helps the animals drift into hibernation. In experiments, mice, which don’t hibernate, strongly preferred to hang out on a hot plate that was 30° Celsius versus one that was cooler. Syrian hamsters (Mesocricetus auratus) and the ground squirrels (Ictidomys tridecemlineatus), however, didn’t seem to notice the chill until plate temperatures dipped below 10° Celsius, notes study coauthor Elena Gracheva, a neurophysiologist at Yale University.
Further work revealed that a cold-sensing protein called TRPM8 wasn’t as easily activated by cold in the squirrels and hamsters as in rats. Found in the sensory nerve cells of vertebrates, TRPM8 typically sends a sensation of cold to the brain when activated by low temperatures. It’s what makes your fingertips feel chilly when you’re holding a glass of ice water. It’s also responsible for the cooling sensation in your mouth after you chew gum made with menthol.
The researchers looked at the gene that contains the instructions to make the TRPM8 protein in ground squirrels and switched up parts of it to find regions responsible for tolerance to cold. The adaptation could be pinned on six amino acid changes in one section of the squirrel gene, the team found. Cutting-and-pasting the rat version of this gene fragment into the squirrel gene led to a protein that was once again cold-sensitive. Hamster TRPM8 proteins also lost their cold tolerance with slightly different genetic tweaks in the same region of the gene.
The fact that it’s possible to make a previously cold-resistant protein sensitive to cold by transferring in a snippet of genetic instructions from a different species is “really quite striking,” says David McKemy, a neurobiologist at the University of Southern California in Los Angeles. As anyone who’s lain awake shivering in a subpar sleeping bag knows, falling asleep while cold is really hard. Hibernation is different than sleep, Gracheva emphasizes, but the squirrels and hamsters’ tolerance to cold may help them transition from an active, awake state to hibernation. If an animal feels chilly, its body will expend a lot of energy trying to warm up — and that’ll work against the physiological changes needed to enter hibernation. For example, while hibernating, small mammals like the ground squirrel slow their pulse and breathing and can lower their core body temperature to just a few degrees above freezing.
Modifications to TRPM8 probably aren’t the only factors that help ground squirrels ignore the cold, Gracheva says, especially as the thermometer drops even closer to freezing. “We think this is only part of the mechanism.”
Scientists also aren’t sure exactly how TRPM8 gets activated by cold in the first place. A detailed view of TRPM8’s structure, obtained using cryo-electron microscopy, was published by a different research group online December 7 in Science. “This is a big breakthrough. We were waiting for this structure for a long period of time,” Gracheva says. Going forward, she and colleagues hope that knowing the protein’s structure will help them link genetic adaptations for cold tolerance in TRPM8 with specific structural changes in the protein.
Cold weather often brings with it hot takes on so-called man flu. That’s the phenomenon in which the flu hits men harder than women — or, depending on who you ask, when men exaggerate regular cold symptoms into flu symptoms. In time for the 2017–2018 flu season, one researcher has examined the scientific evidence for and against man flu.
“The concept of man flu, as commonly defined, is potentially unjust,” Kyle Sue, a clinician at Memorial University of Newfoundland in St. John’s, Canada, writes December 11 in BMJ. Motivated by his own memorable bout of flu, he says, Sue began looking into man flu research and summarizes the work in a review article that’s part of BMJ’s Christmas issue, which traditionally features humorous takes on legitimate research. There might be a reason men come across as wimps. In the United States, more men than women died from flu-related causes from 2007 to 2010 across several age groups, researchers reported in the American Journal of Epidemiology in 2013. An analysis of data on the 2004 to 2010 flu seasons in Hong Kong found that in children and adults, males were more likely to be hospitalized for the flu than females.
Sue isn’t the first to make a case for man flu. A prevailing explanation for men’s susceptibility says that women have higher levels of the hormone estradiol, which can boost the immune system, while men have higher levels of testosterone, which can sometimes suppress the immune system. However, these hormones interact with the immune system in other ways as well.
“There is some evidence that men make weaker immune responses to some viruses than women, but how this happens and whether it is seen across all viruses is still unclear to me,” notes John Upham, professor of respiratory medicine at Queensland University in Australia.
Sue’s review also cites evidence that women respond better to some flu shots than men do. Sex differences in immune response could have real consequences when it comes to vaccine choice, Upham says. It’s also unclear what the evolutionary drivers for immune differences between the sexes might be. And studies of how the male and female immune systems respond differently all come with caveats, Sue notes: Such studies are often in mice rather than humans, have limited data or don’t account for health differences such as smoking habits and tendency to go to the doctor. Upham adds that studying differences in flu cases among men in Western versus non-Western societies could reveal the degree to which learned behavior plays a role in “man flu.”
As much as he’d like to help out his half of the species, Sue says, “we cannot yet conclude that this phenomenon is real, but the current evidence is suggestive that it may be.” Not surprising, his review has met just as much skepticism as previous man flu treatises.
Regardless of the possibility that men may be immunologically weaker than women, Sue says, both flu-stricken men and women alike “could benefit from resting in a safe, comfortable place with a recliner and TV.”
