Connect with us

Science

150,000-Year-Old Human Tooth Is Rare Evidence of the Extinct Denisovans – Gizmodo

Published

 on


The suspected Denisovan molar.
Photo: F. Demeter et al., 2022

Paleontologists in Laos have uncovered an ancient molar that likely belonged to a young Denisovan girl. The discovery is a big deal, as the Laotian cave in which the molar was found is now one of only three spots known to host these enigmatic humans.

In addition to Siberia and the Tibetan Plateau, we can now add Laos to the achingly short list of places that have yielded fossils of an elusive human species known as the Denisovans. A team of paleontologists found the suspected Denisovan molar at the Tam Ngu Hao 2 cave in the Annamite Mountains of Laos. The molar dates to the middle Pleistocene, and it’s the first Denisovan fossil ever to be found in southeast Asia. A paper detailing this discovery is published today in Nature Communications.

Laura Shackelford, an anthropologist from the University of Illinois at Urbana-Champaign and a co-author of the new study, was excited to learn that Denisovans, like their Neanderthal cousins, inhabited a variety of environments, some of them extreme.

The entrance to Tam Ngu Hao 2 cave, also known as Cobra Cave.
The entrance to Tam Ngu Hao 2 cave, also known as Cobra Cave.
Photo: F. Demeter et al., 2022

“Although we only have a few fossils representing the Denisovans, this new fossil from Laos demonstrates that much like modern humans, Denisovans were widespread and they were highly adaptable,” Shackelford explained in an email. “They lived in the cold arctic temperatures of Siberia, in the cold, [oxygen poor] environment of the Tibetan Plateau, and now we know they were also living in the tropics of southeast Asia.”

What’s more, the new discovery “further attests” that southeast Asia was “a hotspot of diversity for the genus Homo” during the middle to late Pleistocene, as the scientists write in their study. So in addition to Denisovans, this part of the world was once home to H. erectus, Neanderthals, H. floresiensis, H. luzonensis, and H. sapiens.

That a Denisovan fossil was found in Laos is not a huge surprise. Traces of Denisovan DNA have been detected within the genomes of modern southeast Asian and Oceanian populations. The Ayta Magbukun—a Philippine ethnic group—have retained approximately 5% of their Denisovan ancestry, the highest of any human group in the world. Denisovans branched off from Neanderthals at some point between 200,000 and 390,000 years ago. They eventually went extinct, but not before interbreeding with modern humans. The Laotian molar is just the 10th Denisovan fossil to be found and the first outside of Siberia and Tibet.

The Annamite Mountains contain an abundance of limestone caves. Each year, Shackelford and her colleagues dispatch geologists to the area in hopes of finding spots worthy of further paleontological investigation.

“In 2018, our geologists spent the morning surveying and returned to the site before lunch with their pockets full of sediment samples that they had collected from a potential new site, what we now know as Tam Ngu Hao 2 or Cobra Cave,” Shackelford told me. “In these first samples, among fragments of fossil animal teeth, we found the tooth.”

By dating the sediment in which the molar was found, the team aged the fossil to between 164,000 and 131,000 years old. A protein analysis of the tooth’s enamel identified the fossil as belonging to a member of the Homo genus, but this test couldn’t pin down the exact species.

Study co-author Fabrice Demeter analyzing the molar.
Study co-author Fabrice Demeter analyzing the molar.
Photo: F. Demeter et al., 2022

“We do know that this is the tooth of a girl who died when she was between about 4 to 8 years old,” said Shackelford. “Since this tooth comes from a child, we are currently doing additional analyses of tooth growth and development.”

Clément Zanolli, an expert on the evolution of human teeth and a co-author of the new study, said the identification of the Denisovan molar arose from multiple lines of morphological evidence. The Laotian molar, he told me, bears a resemblance to teeth found on the partial Denisovan mandible from Tibet, including large tooth dimensions and various distinguishing features that separate it from other Homo species known to inhabit southeast Asia, including Neanderthals and modern humans.

“Among the human groups previously cited, the molar from Laos is closest to Neanderthals, and we know from paleogenetics that Denisovans were a sister group of Neanderthals, meaning that they were closely related and shared morphological features,” Zanolli, who works at the University of Bordeaux, explained in an email. “For these reasons, the most parsimonious hypothesis is that the tooth that we found in Laos belongs to a Denisovan individual.”

It’s not impossible that the molar belonged to a Neanderthal, but if that’s the case, that “would make it the south-eastern-most Neanderthal fossil ever discovered,” according to the paper.

“We are confident it is Denisovan,” Fabrice Demeter, a paleoanthropologist at the University of Copenhagen and a co-author of the study, told me in an email. But to “further confirm our results if needed, genetic analyses would be useful,” he said. Unfortunately, however, “DNA tends to fragment more quickly and intensely in tropical environments,” and it’s for this reason that “no ancient DNA from any Pleistocene human has been sequenced so far,” he added.

The new fossil is important because it affirms something already hinted at by the genetic data—that Denisovans once inhabited a wide area of southeast Asia. What’s more, it “confirms that Denisovans were present in this region and could have met with Late Pleistocene modern humans,” according to Zanolli. And lastly, it shows that Denisovans could live in both cold, high-altitude environments and the tropical forests of southeast Asia.

The Denisovans appear to have been an adaptable group. But that just makes their sudden disappearance some 50,000 years ago all the more mysterious.

Adblock test (Why?)



Source link

Continue Reading

Science

'Permanent bone loss': Calgary study finds astronauts suffer on return to Earth – Cochrane Today

Published

 on


CALGARY — The experience may be out-of-this-world but research indicates those who travel to outer space suffer from increased bone loss. 

A study released Thursday from the Cumming School of Medicine at the University of Calgary followed 17 astronauts before and after their spaceflights. 

The TBone study, conducted over a seven-year period starting in 2015, found that prolonged weightlessness accelerated bone loss in the astronauts. 

“You see on average they lose about two decades of bone. We found that weight-bearing bones only partially recovered in most astronauts one year after spaceflight,” said Dr. Leigh Gabel, an assistant professor in the faculty of kinesiology and lead author of the study. 

“After a year of recovery, they tend to regain about half of that. This suggests the permanent bone loss due to spaceflight is about the same as a decade worth of age-related bone loss on Earth.” 

The researchers travelled to Johnson Space Center in Houston to scan the wrists and ankles of the astronauts before they left for space, on their return to Earth, after six months and then one year. 

The findings, published in Scientific Reports, said the loss happens because bones that would normally be weight-bearing on Earth, such as the legs, don’t have to carry weight in a zero-gravity setting. 

“We’ve seen astronauts who had trouble walking due to weakness and lack of balance after returning from spaceflight to others who cheerfully rode their bike on Johnson Space Center campus to meet us for a study visit,” said Dr. Steven Boyd, director of the McCaig Institute for Bone and Joint Health and professor in the Cumming School of Medicine. 

“There is quite a variety of response among astronauts when they return to Earth.” 

Boyd said new scanning technology has made a world of difference.

“We’re using new technology that can measure the fine details of the bone that are even finer than a human hair in terms of resolution. We can see detail there that wasn’t possible to see before in these astronauts.”

The study found some astronauts who flew on shorter missions — under six months — recovered more bone strength and density in the lower body compared to those who flew for longer durations. 

The study’s next iteration plans to look at the effects of even longer trips to support astronauts who may one day travel beyond the International Space Station. 

“NASA’s really interested in understanding if longer-term spaceflight could lead to even further bone loss, which would not be very good for the astronaut,” said Boyd.

“The next phase is to do a study that would incorporate crew members who spend a year on the International Space Station, which will give us some more insight on whether you lose even more bone after that one year period.”

The University of Calgary’s former chancellor and astronaut, Robert Thirsk, said he knows how difficult it can be to be back on solid ground. 

“Just as the body must adapt to spaceflight at the start of a mission, it must also readapt back to Earth’s gravity field at the end,” he said. 

“Fatigue, light-headedness and imbalance were immediate challenges for me on my return. Bones and muscles take the longest to recover following spaceflight. But within a day of landing, I felt comfortable again as an Earthling.” 

The study was funded by the Canadian Space Agency in partnership with the European Space Agency, NASA and astronauts from North America, Europe, and Asia. 

This report by The Canadian Press was first published June 30, 2022. 

Bill Graveland, The Canadian Press

Adblock test (Why?)



Source link

Continue Reading

Science

James Webb Space Telescope's powers will be revealed in just weeks and scientists can't wait – Space.com

Published

 on


BALTIMORE — The James Webb Space Telescope’s first images are coming soon and scientists can’t wait for us to see them.

On Wednesday (June 29), NASA held a media day at the Space Telescope Science Institute (STScI) in Baltimore in advance of the release of the first science-quality images from the James Webb Space Telescope, which will occur during a live event on July 12. NASA scientists and administrators gave updates on the telescope, discussed Webb’s planned science during its first year in operation and hinted at the contents of some of Webb’s first official images.

“In a real sense, we’re sort of the first users of the observatory and using it for what it’s built for,” Klaus Pontoppidan, Webb project scientist at STScI, said during the news conference. “We recognize that we’re standing on the shoulders of all the scientists and engineers who’ve worked hard for the past six months to make this possible.” 

Live updates: NASA’s James Webb Space Telescope mission
RelatedHow the James Webb Space Telescope works in pictures

Although NASA has already released a few images taken while aligning Webb, the images released on July 12 will be from a fully operational observatory, in full color, and they will show what each of the instruments on the telescope can contribute to science. 

These first images will include a deep-field image peering farther into the past than ever before, scientists said during the briefing. NASA will also release Webb’s first spectroscopic data — precise data on the type of light that Webb detects that will allow scientists to learn more about the ingredients of distant cosmic objects. This data will include Webb’s first spectrum of an exoplanet, scientists said. While the images will be visually spectacular, the new information they reveal using Webb’s infrared-observing powers will distinguish them from images taken by other telescopes. 

“The real difference is the new scientific information and then really opening up the longer wavelengths, infrared wavelengths in a way that we’ve really never seen before,” Jonathon Gardner, deputy senior project scientist for Webb, said during the news conference.

Each of the four instruments on Webb, including its main camera, two near-infrared spectrographs and a mid-infrared camera and spectrograph, will contribute to notable research in its first year of operation. They will collect data at nearly every scale and timescale, from our solar system today to the birth of our universe. Though scientists can detect radiation from near the beginning of our universe, no telescope has ever been able to detect light from some of the universe’s first stars and galaxies. Webb will be the first such observatory. 

Related stories:

“The initial goal for this mission was to see the first stars and galaxies,” Eric Smith, Webb program scientist at NASA, said during the news conference. “Not the first light of the universe, but to watch the universe turn the lights on for the first time.”

Although Webb is already a remarkable feat, its first images represent the start of hopefully decades of science. Webb scientists said they have confirmed that the telescope has enough fuel to carry out science for the next 20 years. Data collected during these years could redefine how we understand our universe.

“This is really only the beginning,” Pontoppidan said. “We’re only scratching the surface.”

Follow us on Twitter @Spacedotcom and on Facebook.  

Adblock test (Why?)



Source link

Continue Reading

Science

Astronauts Can Suffer a Decade of Bone Loss During Months in Space, New Research Suggests – Gizmodo

Published

 on


The new research found that human bones, like the wrist bone pictured here, suffers from accelerated loss of density as the result of long-duration missions in space.
Image: L. Gabel et al., 2022

Long-term exposure to microgravity results in the loss of bone density, and new research reveals the disturbing extent to which this happens and finds that astronauts may never fully recover.

“The detrimental effect of spaceflight on skeletal tissue can be profound,” reads the opening sentence of new research published today in Scientific Reports. Profound is right. The study, led by kinesiologists Leigh Gabel and Steven Boyd from the University of Calgary, found that astronauts who participate in long-duration spaceflights (i.e. missions longer than three months) exhibit signs of incomplete bone recovery even after a full year back on Earth. Long-duration missions, it would seem, result in the premature aging of the bones, particularly bones in the weight-bearing lower extremities.

“We found that weight-bearing bones only partially recovered in most astronauts one year after spaceflight,” Gabel said in a statement. “This suggests the permanent bone loss due to spaceflight is about the same as a decade worth of age-related bone loss on Earth.”

The good news, if there is any in all of this, is that space-based resistance training can serve to limit the amount of bone loss and speed recovery. Previous research by the same team showed that “astronauts were more likely to preserve their bone density and strength if they increased in-flight lower body resistance training volume relative to preflight,” as the scientists write.

The new research shows how dependent we are on gravity for maintaining our bone strength. Each day is a constant struggle against gravity, but all this work does our body good, as it continually strengthens our bones. In space, however, astronauts just float around with barely any physical resistance, resulting in the gradual loss of bone density.

“Bone loss happens in humans—as we age, get injured, or any scenario where we can’t move the body, we lose bone,” Gabel said. “Understanding what happens to astronauts and how they recover is incredibly rare. It lets us look at the processes happening in the body in such a short time frame.”

The team traveled to NASA’s Johnson Space Center in Houston, Texas, to perform the study. In total, 17 international astronauts (14 men and three women) were studied, all of whom performed long-duration missions at some point during the past seven years. The astronauts were evaluated prior to their ISS spaceflights, and then six and 12 months after their return to Earth.

The team took bone scans of specific anatomical areas, namely the tibia, or shinbone, and the forearm. This allowed the scientists to measure the susceptibility of these bones to fracturing (or “failure load,” in the vernacular of kinesiologists), and the amount of bone mineral content and the thickness of bone tissue. They also recorded the astronauts’ workout routines during and after their space missions, including exercises such as deadlifts, running on a treadmill, and cycling.

Of the 17 astronauts studied, 16 exhibited incomplete recoveries of their shinbones (measures of their forearms didn’t really differ a year after the spaceflights). On average, the astronauts exhibited a tibia failure load capacity of 10,579 newtons prior to their spaceflights, but that dropped to 10,084 newtons upon their immediate return to Earth, for a loss of 495 newtons. The astronauts did manage to make a partial recovery in the year following their return, but they were still 152 newtons below their preflight tibia failure load values.

Their bone densities also took a beating. The astronauts had bone densities averaging 326 milligrams per cubic centimeter prior to their time in space, but this dropped to 282.5 mg per cubic centimeter upon their return—a drop of 43.5 mg per cubic centimeter.

“Our findings indicate that microgravity induces irreversible damage to bone strength, density, and trabecular bone microarchitecture,” the scientists wrote in their study. The trabecular bone is a “highly porous form of bone tissue that is organized into a network of interconnected rods and plates,” the function of which is to provide strength and channel external loads away from joints, according to unrelated research.

Unsurprisingly, the bone measures worsened depending on the length of the mission. The eight astronauts who were on the ISS for longer than six months recovered significantly less than those who participated in shorter missions, according to the study. At the same time, the astronauts who recovered the most tibia bone mineral density performed the most in-flight deadlift exercises.

“Since cramped quarters will be a limiting factor on future exploration-class missions, exercise equipment will need to be optimized for a smaller footprint,” the scientists write. “Resistance exercise training (particularly deadlifts and other lower-body exercises) will remain a mainstay for mitigating bone loss; however, adding a jumping exercise to on-orbit regimens may further prevent bone loss and reduce daily exercise time.”

These are important findings, particularly as NASA, through its upcoming Artemis program, is wanting to build a sustainable and prolonged presence on and around the Moon. The new research also speaks to future crewed missions to Mars, which will likewise feature prolonged stays in space. In addition to muscle atrophy and the loss of bone strength, microgravity imposes detrimental affects on the heart, eyes, brain, spine, cells, and overall physical fitness. It’s vital that we learn about all the risks associated with spaceflight and the best ways to mitigate them.

More: Missions to Mars Shouldn’t Exceed Four Years Due to Radiation Risks, Scientists Say.

Adblock test (Why?)



Source link

Continue Reading

Trending