Siberian Neandertals, illustrated here by a father toting his daughter, lived in small groups of close relatives and adult female migrants, a new DNA analysis of 13 ancient hominids shows.
DNA from a group of Neandertals who lived together and a couple of others who lived not far away has yielded the best genetic peek to date into the social worlds of these ancient hominids.
That social scenario comes courtesy of DNA extracted from the teeth and bones of 13 Neandertals found at two caves in the foothills of southern Siberia’s Altai Mountains. Estimates of overall genetic similarity among these Stone Age folks indicate that they formed communities of about 20 individuals, with females often migrating from their home groups to those of their mates, say evolutionary geneticist Laurits Skov of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and colleagues.
Headlines and summaries of the latest Science News articles, delivered to your inbox
Thank you for signing up!
There was a problem signing you up.
It’s unknown whether Altai Neandertals’ small-scale lifestyle was unusual, perhaps due to living in a sparsely populated area, or mirrored Neandertal practices elsewhere in Asia and Europe. Large numbers of Neandertals in Central Europe transformed a forest into grassland around 125,000 years, suggesting they could scale up communities when needed ( SN: 12/15/21 ).
Skov’s group studied the DNA of 11 Neandertals from Chagyrskaya Cave and two Neandertals from Okladnikov Cave ( SN: 1/27/20 ). The Chagyrskaya individuals included a father and his teenage daughter as well as an adult female and an 8- to 12-year-old boy, who was possibly her nephew or grandson.
In the Chagyrskaya group, mitochondrial DNA, typically inherited from the mother, displayed greater diversity than DNA from the Y chromosome, which is inherited only by males. The enhanced mitochondrial DNA variety suggests that adult females frequently moved into that community while the males stayed put, the researchers suspect.
Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
Using DNA from the excavated remains of plague victims, including those buried in a London cemetery from 1348–1349, and from people who died earlier and later, researchers searched for evidence of how the Black Death pushed the immune system to evolve.
A genetic variant that appears to have boosted medieval Europeans’ ability to survive the Black Death centuries ago may contribute — albeit in a small way — to an inflammatory disease afflicting people today.
Researchers used DNA collected from centuries-old remains to discern the fingerprints that bubonic plague during the Black Death left on Europeans’ immune systems. This devastating wave of disease tended to spare those who possessed a variant of a gene known as ERAP2 , causing it to become more common, researchers report October 19 in Nature . That variant is already known to scientists for slightly increasing the odds of developing Crohn’s disease, in which errant inflammation harms the digestive system.
Headlines and summaries of the latest Science News articles, delivered to your inbox
Thank you for signing up!
There was a problem signing you up.
The results show “how these studies on ancient DNA can help actually understand diseases even now,” says Mihai Netea, an infectious diseases specialist at Radboud University Medical Center in Nijmegen, Netherlands, who was not involved with the study. “And the trade-off is also very clear.”
Caused by the bacterium Yersinia pestis , bubonic plague once killed 60 percent of those infected ( SN: 6/15/22 ). In the ancient world, it caused successive waves of misery, the most devastating of which was the Black Death, often dated from 1346 to 1350, an episode thought to have wiped out at least 25 million people — about a third or more of the European population.
By sparing individuals whose immune systems bear certain traits, pathogens such as Y. pestis have shaped the evolution of the human immune system. Studies are teasing out the ways the massive winnowing of the plague altered Europeans’ immune-related genetics.
In this most recent study, population geneticist Luis Barreiro of the University of Chicago and colleagues collected samples containing DNA from the remains of 516 people in London and Denmark who died between 1000 and 1800, including those buried during the Black Death. The researchers examined stretches of DNA for immune-related genes and areas associated with autoimmune and inflammatory diseases.
Within those regions, the researchers identified four locations on chromosomes where they saw strong evidence of genetic changes that appeared to have been driven by the Black Death. In follow-up work, one change stood out: an increase in the frequency of a variant of ERAP2 . When infected with Y. pestis , immune cells from people with this version of ERAP2 more effectively killed the bacteria than cells lacking the variant. Studies of modern populations have linked that same variant to Crohn’s disease.
While the researchers calculate that the ERAP2 variant improved the odds of surviving the Black Death by as much as 40 percent, it only slightly increases the risk for Crohn’s disease. For complex disorders like Crohn’s, “you require probably hundreds, sometimes thousands of genetic variants to actually increase your risk in a significant manner,” Barreiro says.
For some time now, researchers in the field have theorized that adaptations that helped our ancestors fortify their immune systems against infectious diseases can contribute to excessive, damaging immune activity. Earlier studies of plague offer support for this idea. A genetic analysis seeking traces of historical disease in modern Europeans and a study of DNA from the remains of 16th century German plague victims both turned up what appear to be protective changes against the plague that, like the ERAP2 variant, are linked with inflammatory and autoimmune conditions.
Likewise, this latest discovery suggests that genetic changes that have amped up the human immune response in the past, empowering it to better fight off ancient infections, can come at a cost. “If you turn the heat too much, that leads to disease,” Barreiro says.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
Of the rivers analyzed in a new study, the Rogue River (shown) near Agness, Ore., has had the greatest increase in heat wave frequency since 1996. This extreme heat could harm the many salmon relying on the river for survival.
U.S. rivers are getting into hot water. The frequency of river and stream heat waves is on the rise, a new analysis shows.
Like marine heat waves, riverine heat waves occur when water temperatures creep above their typical range for five or more days ( SN: 2/1/22 ). Using 26 years of United States Geological Survey data, researchers compiled daily temperatures for 70 sites in rivers and streams across the United States, and then calculated how many days each site experienced a heat wave per year. From 1996 to 2021, the annual average number of heat wave days per river climbed from 11 to 25 , the team reports October 3 in Limnology and Oceanography Letters.
Headlines and summaries of the latest Science News articles, delivered to your inbox
Thank you for signing up!
There was a problem signing you up.
The study is the first assessment of heat waves in rivers across the country, says Spencer Tassone, an ecosystem ecologist at the University of Virginia in Charlottesville. He and his colleagues tallied nearly 4,000 heat wave events — jumping from 82 in 1996 to 198 in 2021 — and amounting to over 35,000 heat wave days. The researchers found that the frequency of extreme heat increased at sites above reservoirs and in free-flowing conditions but not below reservoirs — possibly because dams release cooler water downstream.
Most heat waves with temperatures the highest above typical ranges occurred outside of summer months between December and April, pointing to warmer wintertime conditions, Tassone says.
Human-caused global warming plays a role in riverine heat waves, with heat waves partially tracking air temperatures — but other factors are probably also driving the trend. For example, less precipitation and lower water volume in rivers mean waterways warm up easier, the study says.
“These very short, extreme changes in water temperature can quickly push organisms past their thermal tolerance,” Tassone says. Compared with a gradual increase in temperature, sudden heat waves can have a greater impact on river-dwelling plants and animals, he says. Fish like salmon and trout are particularly sensitive to heat waves because the animals rely on cold water to get enough oxygen, regulate their body temperature and spawn correctly.
There are chemical consequences to the heat as well, says hydrologist Sujay Kaushal of the University of Maryland in College Park who was not involved with the study. Higher temperatures can speed up chemical reactions that contaminate water, in some cases contributing to toxic algal blooms ( SN: 2/7/18 ).
The research can be used as a springboard to help mitigate heat waves in the future, Kaushal says, such as by increasing shade cover from trees or managing stormwater. In some rivers, beaver dams show promise for reducing water temperatures ( SN: 8/9/22 ). “You can actually do something about this.”
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
Genetically engineering the fungus Aspergillus nidulans (shown in this color-enhanced scanning electron micrograph) to delete certain proteins prevents the production of compounds called mycotoxins.
Food contaminated with fungi can be an inconvenience at best and life-threatening at worst. But new research shows that removing just one protein can leave some fungal toxins high and dry, and that’s potentially good news for food safety.
Some fungi produce toxic chemicals called mycotoxins that not only spoil food such as grains but can also make us sick. Aflatoxins, one of the more dangerous types of mycotoxins, can cause liver cancer and other health problems in people.
Headlines and summaries of the latest Science News articles, delivered to your inbox
Thank you for signing up!
There was a problem signing you up.
“It is a silent enemy,” says fungal researcher Özgür Bayram of Maynooth University in Ireland, because most people don’t notice when food like corn or wheat is spoiled.
For years, researchers have known that some fungi produce these toxins, but didn’t know all the details. Now, Bayram and colleagues have identified a group of proteins responsible for turning on the production of mycotoxins . Genetically engineering the fungus Aspergillus nidulans to remove even just one of the proteins prevents the toxins from being made, the researchers report in the Sept. 23 issue of Nucleic Acids Research .
“There is a long string of genes that is involved with the production of proteins that, in a cascading effect, will result in the production of different mycotoxins,” says Felicia Wu, a food safety expert at Michigan State University in East Lansing who was not involved in the research.
The newly identified proteins act like a key starting a car, Bayram says. The researchers wanted to figure out how to remove the key and prevent the starting signal from going through, meaning that no toxins would be made in the first place.
Bayram and his team identified the proteins in A. nidulans , revealing that four proteins come together to make the key. The researchers genetically engineered the fungus to delete each protein in turn. When any of the four proteins are missing, the key does not start mycotoxin ignition, the team found.
In another study that has yet to be published, deactivating the same group of proteins in the closely related fungus A. flavus , which can make aflatoxins, prevents the production of those toxins, Bayram says. “So this is a big success because we see, at least in two fungi, the same [protein] complex does the same job.”
The new work “is building upon a body of research that’s been done over decades” to prevent fungal contamination of food, Wu says. A range of methods are already used to control such contamination. For instance, because not all A. flavus strains produce aflatoxins, one method to prevent contamination is to sprinkle nontoxic strains onto fields of corn and peanuts, Wu explains. Those fungi multiply and can help prevent other toxic strains from gaining a foothold.
This research is one of several ways that researchers are using genetic engineering to try to combat these toxins in food ( SN: 3/10/17 ). One future application of the new research could be to genetically tweak a toxin-making fungus and then possibly use it on crops and elsewhere. “We can basically prevent aflatoxin contamination in food, for example, in the field, even in the warehouses, where a lot of contamination takes place,” Bayram says.
Fungi and fungi-like organisms known as water molds are estimated to ruin a third of the world’s food crops each year . If that contamination could be prevented, Bayram estimates the saved food would be enough to feed 800 million people in 2022.
The new research is a good start, Wu says, but it will still be a “challenge to try to understand how this can be operationalized for agricultural purposes.” It’s unclear how scalable the technique is, she says, and getting U.S. regulatory agencies to approve the use of a genetically modified fungus on key food crops might be difficult.
Deborah Balthazar is the Fall 2022 science writing intern at Science News . She holds a B.A. in biology with minors in English and chemistry from Caldwell University and is currently pursuing a master’s degree in science journalism from New York University.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
Colonoscopies are a common screening test for colorectal cancer in the United States. There are important limitations to a recent study reporting that the procedure isn’t as effective at screening as previously thought.
A recent study reported a smaller-than-expected benefit from screening colonoscopies. But the study has important caveats, gastroenterologists say, making it ripe for misinterpretation if that context isn’t included.
The study was the first randomized controlled trial — widely considered the gold standard for testing medical interventions — of the procedure. Published online October 9 in the New England Journal of Medicine , the study followed participants invited to have a colonoscopy and compared how they fared with participants who weren’t invited to undergo the procedure . The risk of colorectal cancer at 10 years was reduced by 18 percent in the invited group. But there wasn’t a meaningful difference in the risk of death from colorectal cancer between the two groups, the study reported.
Headlines and summaries of the latest Science News articles, delivered to your inbox
Thank you for signing up!
There was a problem signing you up.
This was disappointing, gastroenterologists say, as past research has shown screening colonoscopies to be more effective in reducing the risks of developing and dying from colorectal cancer. Those previous data were from observational studies, which don’t randomly assign patients to get, or not get, a treatment.
But a closer look at the details of the new study reveals why it shouldn’t be interpreted as a slam-dunk against the screening test. First, fewer than half of the people invited to have a colonoscopy actually did. The study also didn’t follow patients long enough to fully assess the risk of death from colorectal cancer. And some of the physicians who did the procedure didn’t meet a minimum quality benchmark.
These issues limit what this study can tell us about screening colonoscopies. On top of that, this study should not be used to cast doubt on colorectal cancer screening in general, says Folasade May, a gastroenterologist and health services researcher at UCLA Health. “Screening is effective, and it saves lives,” she says. “We have enough data to promote screening.”
Colorectal cancer is the second-leading cause of cancer deaths for men and women combined , according to the American Cancer Society. It’s expected to kill more than 52,000 Americans in 2022. There are racial disparities in who gets and dies from the disease. Rates of incidence and death are 21 percent and 44 percent higher in Black men compared with white men; the rates for Black women compared with white women are 18 percent and 31 percent higher, respectively.
The U.S. Preventive Services Task Force recommends screening for colorectal cancer in adults ages 45 to 75 years old ( SN: 5/31/18 ). There are different screening options, including stool-based tests; colonoscopy, which examines the whole colon; and sigmoidoscopy, which looks at a portion of the colon. Average-risk individuals — those who don’t have a family history of colorectal cancer or other conditions that increase risk — can choose the option that works for them. “We just want people to get screened,” says gastroenterologist Sophie Balzora of the New York University Grossman School of Medicine. “The best test is the one that gets done.”
The fecal immunochemical test, or FIT, and colonoscopy are commonly performed in the United States. The FIT detects tiny amounts of blood in the stool, which can be a sign of colorectal cancer, and is done at home.
During a colonoscopy, a physician looks for and removes polyps, growths of tissue that can become cancerous. But the procedure’s expense, time and preparation can be prohibitive for some patients, says Carol Burke, a gastroenterologist at the Cleveland Clinic. People may not have the flexibility to take time off work for the procedure or have someone who is available to drive them home, for example. To complete a colonoscopy, “you have to be sure that you can address the patient’s barriers,” Burke says.
The potential barriers to getting a colonoscopy mean it’s not enough to just tell someone to do it. That’s also the case in Poland, Norway and Sweden, where colonoscopies are not commonly used to screen for colorectal cancer. One-third of roughly 84,000 study participants from these countries were invited to get colonoscopies. The other two-thirds made up the “usual care” group. But “the intervention was an invitation, not a colonoscopy,” Balzora says. Only 42 percent of the participants invited to get the procedure had one. The majority of the invitees turned the invitation down.
“If you don’t actually have the test, it can’t possibly protect you,” says gastroenterologist Aasma Shaukat of the New York University Grossman School of Medicine.
Another limitation of the new study has to do with time. Colon cancer develops slowly. Most polyps don’t become cancerous, but for those that do, it can take 10 years or more. Then it takes time for the cancer to spread and become fatal. At least 15 years of follow up are needed to really look at the impact on colorectal cancer deaths, Shaukat says, so the study’s report at 10 years isn’t long enough.
And the quality of the colonoscopies performed in the study varied. One standard is the adenoma detection rate, the number of colonoscopies that turn up a precancerous polyp, or adenoma, divided by the number of colonoscopies performed over a period of time. In the new study, nearly 30 percent of the physicians doing the procedures had rates below the recommended minimum quality rate.
In their paper, the study’s authors acknowledge these limitations. They note that the colonoscopy-by-invitation approach may have underestimated the benefits of the procedure. They say that reductions in risk of cancer are expected to appear before reductions in risk of death; the team will report results again at 15 years of follow-up. And, they add, differences in quality benchmarks among practitioners may have affected the detection of cancer.
The new study needs to be considered among other evidence for the effectiveness of screening colonoscopies, Shaukat says. For example, an analysis that combined observational studies of colonoscopy, published in 2014 in the British Medical Journal , reported that the procedure reduces both colorectal cancer incidence and mortality by close to 70 percent .
Another observational study looked at an organized screening program that used colonoscopy, sigmoidoscopy and FIT. The program led to a boost in screening that was linked to a 25 percent decrease in the annual incidence of colorectal cancer from 2000 to 2015 and a 52 percent drop in deaths from the cancer , researchers reported in Gastroenterology in 2018.
There is also a randomized controlled trial going on now in the United States that will compare head-to-head the effectiveness of screening with colonoscopy or FIT in average-risk people. So there’s more data to come. The new study “isn’t the end-all, be-all study,” May says. “We haven’t closed the door on colonoscopy.”
Aimee Cunningham is the biomedical writer. She has a master’s degree in science journalism from New York University.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
Planet-building disks of gas and dust (one pictured) survive for millions of years longer around orange and red dwarf stars than astronomers realized, a new study suggests.
Good news for late bloomers: Planets may have millions of years more time to arise around most stars than previously thought.
Planet-making disks around young stars typically last for 5 million to 10 million years , researchers report in a study posted October 6 at arXiv.org. That disk lifetime, based on a survey of nearby young star clusters, is a good deal longer than the previous estimate of 1 million to 3 million years.
“One to three megayears is a really strong constraint for forming planets,” says astrophysicist Susanne Pfalzner of Forschungszentrum Jülich in Germany. “Finding that we have a lot of time just relaxes everything” for building planets around young stars.
Headlines and summaries of the latest Science News articles, delivered to your inbox
Past studies have estimated disk lifetimes by looking at the fraction of young stars of different ages that still have disks — in particular, by observing star clusters with known ages. But Pfalzner and her colleagues discovered something odd: The farther a star cluster is from Earth, the shorter the estimated disk lifetime. That made no sense, she says, because why should the lifetime of a protoplanetary disk depend on how far it is from us?
The answer is quite simple: It doesn’t. But in clusters that are farther away, it’s harder to see most stars. “When you look at larger distances, you see higher-mass stars,” Pfalzner says, because those stars are brighter and easier to see. “You basically don’t see the low-mass stars.” But the lowest-mass stars constitute the vast majority. These stars, orange and red dwarfs, are cooler, smaller and fainter than the sun.
So Pfalzner and her colleagues examined only the nearest young star clusters, those within 650 light-years of Earth, and found that the fraction of stars with planet-making disks was much higher than that reported in previous studies. This analysis showed that “the low-mass stars have much longer disk lifetimes, between 5 and 10 megayears,” than astronomers realized, she says. In contrast, disks around higher-mass stars are known to disperse faster than this, perhaps because their suns’ brighter light pushes the gas and dust away more quickly.
“I wouldn’t say that this is definite proof” for such long disk lifetimes around orange and red dwarfs, says Álvaro Ribas, an astronomer at the University of Cambridge who was not involved with the work. “But it’s quite convincing.”
To bolster the result, he’d like to see observations of more distant star clusters — perhaps with the James Webb Space Telescope — to determine the fraction of the faintest stars that have preserved their planet-making disks between 5 million and 20 million years ( SN: 10/11/22 ).
If the disks around the lowest mass stars do indeed have long lifetimes, that may explain a difference between our solar system and those of most red dwarfs, Pfalzner says. The latter often lack gas giants like Jupiter and Saturn, which are about 10 times the diameter of Earth. Instead, those stars frequently have numerous ice giants like Uranus and Neptune, about four times the diameter of Earth. Perhaps Neptune-sized planets arise in larger numbers when a planet-making disk lasts longer, Pfalzner says, accounting for why these worlds tend to abound around smaller stars.
Ken Croswell has a Ph.D. in astronomy from Harvard University and is the author of eight books, including The Alchemy of the Heavens: Searching for Meaning in the Milky Way and The Lives of Stars.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
