Latest from Scientific American
Scientific American
an hour ago
- Science
- Scientific American
First Near-Complete Denisovan Skull Reveals What This Ancient Human Cousin Looked Like
A prominent brow ridge with a brain as large as modern humans and Neanderthals — that's what the archaic human group, the Denisovans, looked like, according to work published this week in Cell and Science. Palaeontologists used ancient molecules to identify a cranium found near Harbin in northeastern China as belonging to the group. It's the first time a near-complete skull has been definitively linked to the extinct people. The fossil, which is at least 146,000 years old, ends a decade and a half of speculation about the Denisovans' appearance. This had remained a mystery since scientists identified them from unique DNA taken from a finger bone found in a Siberian cave in 2010. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. 'It's really exciting to finally have Denisovan DNA from a nearly complete cranium,' says Janet Kelso, a computational biologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. 'We finally have some insights into the cranial morphology of the Denisovans,' she says. 'It's really exciting to finally have Denisovan DNA from a nearly complete cranium,' says Janet Kelso, a computational biologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. 'We finally have some insights into the cranial morphology of the Denisovans,' she says. Dragon Man The 'massive' cranium — the upper portion of the skull, lacking the lower jawbone — is one of the best preserved of all archaic human fossils, according to researchers who first described it in 2021. Qiang Ji, a palaeontologist at Hebei GEO University in Shijiazhuang, China, obtained the specimen from an unnamed man in 2018. The man — who Ji suspects discovered the artefact himself but failed to report it to authorities — claimed that his grandfather unearthed the fossil in 1933 during bridge-construction work over Long Jiang (which means dragon river), and buried it in an abandoned well, where it remained until a deathbed confession. In 2021, Ji and his colleagues determined that the 'Dragon Man' fossil represented a new archaic human species, which they crowned Homo longi 4. Molecular sleuthing When Ji published those findings, Qiaomei Fu, a geneticist at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, got in touch. Fu worked on the very first Denisovan DNA from the Siberian finger bone and wanted to see whether the Dragon Man fossil contained any ancient molecules. She and her team first attempted to extract ancient DNA from a part of the skull called the petrous bone — often a good source — and from an attached tooth. They didn't recover any genetic material but did extract and sequence fragments from 95 ancient proteins from the petrous samples. Fu compared these with Neanderthal, modern human and Denisovan sequences. One protein sequence from the Harbin fossil was identical to that of a protein from the Siberian finger bone, as well as from Denisovans uncovered in Tibet and Taiwan, but differed from proteins in modern humans and Neanderthals. That suggested the Dragon Man individual was a Denisovan. Fu's team identified two further, less conclusive, protein matches. It's the second time this year that researchers have used ancient proteins to identify a fossil as Denisovan. In April, Takumi Tsutaya, a bioarchaeologist at the Graduate University for Advanced Studies in Kanagawa, Japan, and his colleagues identified a Taiwanese jawbone as belonging to a Denisovan. Tsutaya says that he was amazed to learn that another Denisovan has already been identified. But Fu says that she wanted further evidence. She turned to a tiny chip of calcified dental plaque, or calculus. Fu looked for DNA from the host among the bacterial DNA in the sample. And she found it. Genetic sequences from the maternally inherited mitochondrial genome of the Dragon Man skull were most closely related to early Denisovans from Siberia, which were between 187,000 and 217,000 years old. Fu says that this is the first time that host DNA has been recovered from dental calculus from the Palaeolithic era, which ended 12,000 years ago. Rikai Sawafuji, a geneticist at Kyushu University in Fukoka, Japan, who worked on the Taiwanese fossil, was surprised that the team recovered human DNA from the calculus, given that no DNA was recovered from the petrous bone. She says this could spur other researchers to analyse ancient plaque from Palaeolithic fossils. 'If there is some dental calculus,' she says, 'people can extract human mitochondrial DNA from those samples' to learn more about prehistoric human migrations. Potentially more important is that scientists now have a Denisovan cranium that researchers can use to identify other Denisovan specimens in their collections, even if no ancient DNA or protein can be found.
Scientific American
3 hours ago
- Science
- Scientific American
Daring Hurricane Hunter Flights Make Forecasts More Accurate. But They Could Face Cuts
CLIMATEWIRE | NOAA's famed Hurricane Hunter airplane missions significantly increase the accuracy of hurricane forecasts, according to new research that comes as the government's weather analysis system faces potentially debilitating cuts. The Hurricane Hunter program, which sends aircraft into tropical cyclones to gather data for scientists to analyze, improves the accuracy of hurricane forecasts by up to 24 percent, according to a study published in May. The study adds to research showing the value of the Hurricane Hunter program as President Donald Trump's proposed budget cuts put them in jeopardy. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. Trump's proposed budget for fiscal 2026 does not appear to target the Hurricane Hunter program. But it would end funding for NOAA's research network including the University of Miami's Cooperative Institute for Marine and Atmospheric Studies, whose scientists collect measurements on the Hurricane Hunter flights. The Trump administration earlier this year laid off several employees involved in the Hurricane Hunter missions amid widespread staff reductions at NOAA and other federal agencies. This year's Hurricane Hunter flights are expected to proceed as usual. But scientists are concerned about the consequences of reduced data collection missions at NOAA, suggesting that weather models could suffer. Staff reductions earlier this year forced multiple National Weather Service offices to reduce or curtail their daily weather balloon launches that collect atmospheric data. Experts say some forecasts have already declined as a result. Hurricane Hunter missions provide similarly useful data, scientists say. The aircraft — some operated by the Air Force and others operated by NOAA — zoom through tropical cyclones as they strengthen over the ocean and deploy special instruments that measure temperature, humidity, wind speeds. and other variables inside and around the storms. For their May study, researchers Melissa Piper and Ryan Torn of the University of Albany in New York focused on missions conducted with NOAA's Gulfstream IV jets, often called G-IV jets. They compared the accuracy of forests that included Hurricane Hunter data with a baseline model and found forecasts incorporating the data were as much as 24 percent more accurate than forecasts without the data. Hurricane Hunter flights are typically reserved for hurricanes expected to make landfall in the U.S. or nearby islands. The researchers also found that forecasts for weaker storms seemed to benefit the most from Hurricane Hunter data. And while hurricane forecasts continue to update for hours or days as the storms evolve, the forecasts saw their most dramatic improvements immediately after Hurricane Hunter measurements were added. The researchers couldn't say for sure that any individual forecast would have performed less accurately without the Hurricane Hunter data. Instead, the study suggests that forecasts involving the G-IV flights performed better on the whole than the models without them, suggesting hurricane forecasts could suffer with cuts to the Hurricane Hunter program. Meteorologists have warned that other proposed cuts to NOAA threaten the nation's weather forecasting capabilities. The White House's proposed elimination of NOAA's Office of Oceanic and Atmospheric Research would kill some of the scientific projects that help weather models improve over time. 'There's gonna be a great price to be paid by our society,' former NOAA chief scientist Craig McLean said Tuesday at a panel of former NOAA experts. Forecasts of extreme weather that leads to wildfires, floods and heatwaves all perform well today because of scientific advancements at NOAA, McLean said.
Scientific American
11 hours ago
- Science
- Scientific American
How Does a Gravitational Slingshot Work?
You've probably watched this sort of science-fiction scene more than once: some stalwart starship captain and their crew are fleeing from aliens/escaping a supernova /running out of fuel and are seemingly out of options, about to get eaten/vaporized/stuck. But then, just ahead, they spot a planet! So they head right for it, rockets blazing, then dive down and use its gravity to slingshot to safety. Hooray! Cue the triumphant music. So it goes on the silver screen, at least. But does this maneuver work in real life? Yes! Well, not so much the way it's done in movies—but it is an actual thing. It's widely known as a gravitational slingshot, though most scientists refer to it as a gravitational assist, and it's an essential tool for most interplanetary missions. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. The idea seems simple enough. As a spacecraft approaches a massive object, say, a planet, the gravity of the planet bends its trajectory, changing the spacecraft's direction. But there's more to it than that: the spacecraft can actually use the planet's gravity to speed up or slow down after this maneuver, allowing easier voyages to the outer or inner planets, respectively. While the trajectory-bending part seems obvious enough, that speed-up-or-slow-down part is pretty counterintuitive. It's related to the symmetry of gravity. If you hold a rubber ball some distance from the ground and drop it, the ball will accelerate as it falls, speeding up until impact. Then it bounces, moving upward and decelerating as it does so. It will eventually come to a stop, whereupon you can catch it or let it fall again. But either way, it can't bounce any higher than the height from which you dropped it. It gained kinetic energy—the energy of motion—as it fell but then lost it once again postbounce as it slowed on its way back up. This action is symmetric, so at best (if you had a perfectly elastic ball and did this experiment in a vacuum), it would bounce to the same height from which you dropped it. The same is true for a spacecraft approaching a planet. The world's gravity will accelerate you as you fall in, you'll whip around at closest approach (that's the 'slingshot' part), and then you'll lose that extra velocity as you move away because the planet's gravity is still pulling on you. As that gravitational grip slips away, the spacecraft will be moving relative to the planet at the same speed at which it initially approached. So if all the bonus speed is lost on the way out, how can this maneuver be used to accelerate a spacecraft? The key is in the phrase 'relative to the planet.' If you approach the planet at, say, 20 kilometers per second (km/s), you'll leave with the same speed. But that's your speed measured against the planet. At that same time, crucially, the planet is also orbiting the sun. If you approach the planet from behind (that is, in the direction of its motion), then, as the planet's gravity gives you a boost, it also, in a heliocentric sense, pulls you along, adding some of its orbital velocity to yours. That gives you a kick relative to the sun, speeding you up on your way to your destination. In essence, the spacecraft gets a net gain in speed by stealing a little bit of the planet's orbital kinetic energy. In turn, this means the planet actually slows a bit in its orbit around the sun—which sounds dangerous! But fear not: the planet slows in proportion to how much more massive it is than the spacecraft. Given a typical one-ton probe compared with a multisextillion-ton world, the planet doesn't noticeably slow at all. You could launch a million probes at it and never be able to tell the difference in its orbital speed. A bacterium bouncing off you while you're out walking would have a far larger effect on you. The reason it's worthwhile to go to the trouble of gravitational assists is that spacecraft are launched by rockets, which can only accelerate to some top speed. For our current rocketry, these speeds are so low and the interplanetary distances so great that even the fastest, most direct voyages take years (or even decades for destinations in the outer solar system). You can load the spacecraft with more fuel to burn to go faster, but there's a limit to that, too. Fuel has mass, and you'd need to accelerate that extra mass, which takes more fuel, which has more mass. This catch-22 is described by what is called the rocket equation, and it means the amount of fuel you must add to move even slightly faster reaches prohibitive scales very quickly. So shaving time off your voyage requires some other method—such as siphoning speed from a big, juicy planet along the way! For example, the Cassini probe to Saturn, which launched in 1997, was a huge spacecraft, the size of a school bus, and had a mass of 2.5 metric tons without fuel. (The addition of the fuel it needed to fulfill its mission at Saturn, along with the launch vehicle and other equipment, tipped the scales to 5.7 metric tons.) It would've taken practically forever to get to Saturn with the rockets we had then. So the mission planners took advantage of Jupiter, sending the spacecraft past it on a speed-boosting slingshot maneuver that shaved significant time off the journey. In fact, just to get out to Jupiter in the first place, Cassini also performed two fuel-saving flybys of Venus and one of Earth, stealing planetary orbital energy every time. A gravitational assist works the other way, too. Earth orbits the sun at more than 30 km/s, so firing a probe at the sun or the inner planets is extremely hard because of all that sideways velocity. Instead mission planners prefer a more circuitous route. They launch the spacecraft with enough velocity in the opposite direction of Earth's path around the sun to drop in front of, say, Venus, where it can then donate some of its orbital energy to the planet to drop toward the sun even more. BepiColombo, a joint European Space Agency and Japan Aerospace Exploration Agency mission to Mercury, did exactly this, passing Earth once and Venus twice to get in Mercury's vicinity. Even then, it had to do a total of six gravity assists past Mercury to match the planet's orbital speed around the sun. The last assist was in January 2025, and it will enter Mercury orbit in November 2026. Gravitational assists are an emblematic example of why space travel is hard —it is exactly rocket science, after all. Gravity is the biggest culprit; just getting away from Earth in the first place is the largest part of the problem. It's ironic, then, that gravity can make reaching most of the rest of the solar system so much easier.
Scientific American
11 hours ago
- Science
- Scientific American
Science Quiz: Event Horizons and Flesh-Eating Parasites
Allison Parshall is an associate editor at Scientific American covering mind and brain. She writes the magazine's Contributors column and weekly online Science Quizzes. As a multimedia journalist, she contributes to Scientific American 's podcast Science Quickly. Parshall's work has also appeared in Quanta Magazine and Inverse. She graduated from New York University's Arthur L. Carter Journalism Institute with a master's degree in science, health and environmental reporting. She has a bachelor's degree in psychology from Georgetown University. Follow Parshall on X (formerly Twitter) @parshallison
Scientific American
11 hours ago
- Health
- Scientific American
Testosterone Therapy Is Booming. But Is It Actually Safe?
As more men turn to testosterone replacement therapy (TRT) for energy, mood and muscle, experts warn the risks are still not fully understood. By , Stephanie Pappas, Fonda Mwangi & Alex Sugiura This episode was made possible by the support of Yakult and produced independently by Scientific American 's board of editors. Rachel Feltman: For Scientific American 's Science Quickly, I'm Rachel Feltman. Whether it's framed as a cure-all for fatigue and low libido or a shortcut to gaining muscle mass, testosterone replacement therapy, or TRT, is all over the Internet these days. But how much of the hype is actually backed by science? On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. Here to help us make sense of the testosterone boom is Stephanie Pappas, a freelance reporter based in Colorado. Stephanie recently covered the growing popularity—and availability—of TRT for Scientific American. Thanks so much for coming on to chat. Stephanie Pappas: Thank you. Feltman: So you recently wrote about testosterone replacement therapy for Scientific American. For folks who are not on the right part of the Internet to have heard all about this—or maybe staying off the wrong parts [laughs] of the Internet, depending on your perspective—what's going on with TRT right now? Pappas: Well, testosterone replacement therapy has become extremely popular. It has been something that's been in the background for many, many years. Synthetic testosterone was first invented in 1935, but for a long, long time people thought that testosterone replacement, if it was used for any kind of symptoms men might be having, that it could cause prostate cancer. And then it was believed, perhaps, it could cause heart disease or cardiovascular events like a stroke or a heart attack. As it turns out the last few years we found that it doesn't really cause these really serious events. However, a lot less is known about the long-term health impacts. People are really flocking to TRT largely as a result of word of mouth. There are a lot of private clinics that offer this out of pocket, so you don't have to have an insurance company agree that you need it. And people on social media are using it for just a litany of different symptoms, and it can be anything from muscle-building to fatigue to mood problems and irritability, and it's kind of being pitched as a cure-all for a lot of different things. Feltman: And what evidence is there for the benefits of testosterone replacement therapy, maybe starting with people who actually have low testosterone? Pappas: Yeah, so there is such a thing as low testosterone. No one exactly agrees on what the cutoff is, and probably that's because there's a lot of variability in our hormones—like, anyone who's ever tried any sort of hormone treatment, including birth control or HRT [hormone replacement therapy], can tell you that people respond really differently. So for men who really do have low testosterone, the evidence suggests that you can see some benefits in mood if you have major depression. You may see some improvements in energy. The most well-established result from the studies of TRT is that you'll probably see a little boost in libido if you have low testosterone and you now start taking TRT, and that's because testosterone works in the brain to increase sexual desire. Feltman: Hmm. Pappas: For men who don't have low testosterone, which are many of the men who are now getting treatment, the evidence for benefits is much, much lower. We don't know if you really see much besides additional muscle-building abilities. Feltman: And what are the potential downsides? You mentioned that one of the reasons there's such a boom right now is that research has showed that the connection to prostate cancer is not concerning the way we once thought it was. But what about other issues that can come up when you don't have low testosterone and you start taking a bunch of testosterone? Pappas: Right, so if you are taking a testosterone supplement, your body actually shuts down its own testosterone production. There's this neat little feedback loop that says, 'Oh, if the testosterone's high in the blood, we're going to just kind of ramp it down.' And a side effect of that is, actually, because testosterone is involved in sperm production, your body will also stop producing sperm. So as more younger men turn to TRT, we are seeing that men who are interested in still having children are finding they're losing their fertility. Oftentimes men are told, 'Oh, you'll recover it once you stop.' But that can actually be slow and complicated, so urologists in the field often see men who aren't understanding why they're not, you know, able to get their partner pregnant, and they may have tried for quite some time. Feltman: Right, and, you know, not that this is the reason that's upsetting, but there is also kind of an irony there because a lot of the marketing is sort of stereotypical masculinity, so it's not surprising that people are caught off guard by that potential downside. Pappas: Yes, absolutely. They are really marketing this—if you go, you can see it on billboards or online—these ads are all about muscles, they're about machoism. And oftentimes the reports from some of these freestanding clinics is that men are not being told all the information about all the side-effect possibilities. Feltman: When you say that regaining fertility after these treatments can be complex and slow, could you walk us through what you mean by that? Pappas: Sure, because your own testosterone levels and sperm production drop, you're going to have to, usually, get off the testosterone. That can really lead to a hormone crash; since your body is, really, at that point in quite low testosterone, you may feel irritable, you may feel fatigue. So you're gonna have to go through that—a bit of a roller coaster. Doctors will prescribe some medications that can help even out your levels and help encourage your body to start producing its own sperm again. That can take some time; it can be a little expensive. Urologists can help you, though. But they do say that they are concerned that men have a, often, too rosy picture of what that's gonna look like. It can take up to two years to recover full fertility, there's kind of an unknown as to whether sperm quality will be quite as high as it was beforehand. And as anyone who's trying to have kids knows, two years can be quite a while when you're dealing with fertility problems. Feltman: Yeah, so let's talk some more about those freestanding clinics. You know, in addition to TRT, you know, being more in demand and more in the conversation, it also seems like it's more accessible than ever, so what are some of the sort of concerning characteristics of these clinics that are popping up? Pappas: Well, you don't wanna paint all clinics with the same brush ... Feltman: Sure. Pappas: Because there is a wide variety of care out there. So it can be any provider that can prescribe—because testosterone is a controlled substance—but they may not really be running you through a full workup, as a urologist or an endocrinologist affiliated with a practice or a hospital system might do. The recommendations from professional societies suggest you get two testosterone tests on different days because testosterone levels swing wildly. I could not find anyone who'd reported to me that they'd gotten two tests. I can't say that there aren't clinics that do it. Typically you're gonna get one test. Typically they are motivated to prescribe what they can to you. The problem, often, is that because of this long-term fear around testosterone, is that many primary care doctors are nervous about prescribing it or don't feel that they've been trained. I spoke to one man who, actually, his doctor said, 'Yes, your testosterone is undeniably low, but I don't know what to do about it. Maybe just go to one of these clinics, and they can help you.' His experience in that clinic, unfortunately, was that they kind of gave him a generic prescription, did not really test through his levels, didn't really talk through, you know, alternative treatments or other things he might look at doing. So he felt his loss and he ended up looking on Reddit for advice, which, as we all know [laughs], is a real hit-and-miss proposition ... Feltman: Sure. Pappas: So men are often kind of left searching for their own information, and they may not have good sources of information. Feltman: And the experts that you spoke to, what do they wanna see change about the way we're treating TRT? Pappas: The first step is that a lot of physicians who specialize in hormone replacement therapy for men would like to see more awareness among primary care physicians and other doctors that men might go to, because if they could coordinate that care in a really responsible way, there are probably many men who could benefit: they do have low testosterone but haven't ever thought about being tested. And then the other side of this is just patient education. If you're going to consider going to a clinic, don't just go somewhere that will happily hand you a prescription. Really look for someone who is going to sit down with you, who is going to talk through lifestyle changes, who's going to look at alternative problems. So one doctor I spoke to said, 'The first thing we do is we look for sleep apnea in our patients. If we can cure that, oftentimes we don't need to look at their testosterone levels again.' And don't be in a rush to walk out that first day with a prescription that might be too high for you and might lead to side effects like acne, or another side effect you can see is an overgrowth of red blood cells that can lead you to need to have to donate blood every month to keep that in normal range. Look for something that's not going to cause the side effects that can really affect your life in the long term. Feltman: Sure, well, thank you so much for coming on to talk us through your feature. I really appreciate it. Pappas: Thank you so much. Feltman: That's all for today's episode. You can read Stephanie's full story on TRT in the July/August issue of Scientific American. We'll be back next week with something special: a three-part miniseries on bird flu. From avian influenza's wild origins to its spread across U.S. farms to the labs trying to keep it from becoming the next pandemic, this looming public health threat has a lot of moving parts, but we'll get you all caught up. Science Quickly is produced by me, Rachel Feltman, along with Fonda Mwangi, Kelso Harper, Naeem Amarsy and Jeff DelViscio. This episode was edited by Alex Sugiura. Shayna Posses and Aaron Shattuck fact-check our show. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for more up-to-date and in-depth science news.
