Ghostly particles from space are giving us a new view of our galaxy.



Known as neutrinos, these subatomic particles have little mass and no electric charge. Theyre sometimes called ghost particles. Thats because they easily pass without a trace through gas, dust and even stars. High-energy neutrinos zip everywhere throughout the cosmos, carrying information about distant places. But where the particles come from has typically been a mystery.



Lets learn about ghost particles



Now, researchers found the first signs of high-energy neutrinos coming from within our Milky Way. They mapped the particles to create a new image of our galaxy. Its the first made with something other than light.





The map also hints at possible sources for these high-energy neutrinos. They could be the remains of past supernovas star explosions. Or they might come from the cores of collapsed supergiant stars or other unidentified objects. More research is needed to figure out the sources for all these neutrinos.



The new map of our galaxy was unveiled June 30 in Science.



Previously, only a few high-energy neutrinos have been traced back to their potential birth. They all came from outside the Milky Way. Two appeared to come from black holes shredding their companion stars. Others came from a type of galaxy called a blazar.



Explainer: Stars and their families



Its clear now that researchers are spotting neutrinos from both inside and outside our galaxy, says Kate Scholberg. Shes a physicist at Duke University in Durham, N.C., who did not take part in the new mapping project. Theres so much more to learn, she says. It can be tremendous fun to figure out how to see the universe with neutrino eyes.



Those neutrino eyes might one day allow us to see distant objects in a way that no other telescopes can match.



Some telescopes rely on visible light. Others pick up X-rays, gamma rays or the charged particles that make up cosmic rays. All of those types of light can be deflected or absorbed as they travel through space. Neutrinos, though, can cross huge expanses without being deflected. This allows the particles to tell us about very distant objects.




Three ways to map the Milky Way



Here are views of the Milky Way in visible light (top), gamma rays (middle) and high-energy neutrinos (bottom). Dust obscures portions of the visible-light map, and a variety of sources can generate gamma rays. Neutrinos have the potential to pinpoint remnants of supernovas, cores of collapsed stellar giants and other cosmic features.


IceCube Collaboration/Science 2023IceCube Collaboration/Science 2023





New look at old data



The ability of neutrinos to pass through things so easily also makes them extremely hard to detect. Scientists found the Milky Way particles using a neutrino detector in Antarctica. Called IceCube, this detector is embedded deep in the ice. To better detect ghostly neutrinos, its enormous. Its 5,160 sensors are arranged in a cube one kilometer (3,281 feet) on each side.



Even so, the experiment sees only a tiny share of the neutrinos that zip through space. IceCube scientists observe 100,000 or so neutrinos a year. Some of these neutrinos leave tracks in the detector. The scientists can sometimes trace these tracks back to the neutrinos source. Most of the neutrino signals that IceCube picks up, though, are a type called a cascade event. These leave bursts of light in the detector, but do not reveal a neutrinos origins as well as tracks can.



Astronomers used to throw away data on cascade events, says Naoko Kurahashi Neilson. Shes a physicist at Drexel University in Philadelphia, Pa. Those data can hold useful information about where the neutrinos come from. Its just hard to pick out which of those tens of thousands of cascade events are most important.





Kurahashi Neilson and her team took up the challenge. They dug through a decade of IceCube cascade-event data. They enlisted the help of an artificial-intelligence system known as a neural network. You can train the neural nets to identify which events are worth keeping, Kurahashi Neilson explains.



She pioneered this approach in 2017. Over the years, Kurahashi Neilson has steadily improved it. She and her colleagues have now used it to identify the neutrinos used to make the new map.



Its an impressive analysis, Scholberg says. And the technique may have the potential to be developed even more. Clearly a lot more work needs to be done, she says. But its very exciting to see the basic expectation [of Milky Way neutrinos] verified.

It sounds unbelievable, but scientists from Harvard University believe our entire universe may have been created in a lab by an advanced civilization with an immense knowledge of physics and how to control it.

For pranksters, there is no better holidaythan April Fools' Day. Celebrated annually on April 1, it is the only day of the year when fun, harmless hoaxesgo unpunished. Themischievous holiday has murky origins. Somebelieve itstarted in 1582when France transitioned from the Julian calendar which began the year around April 1 to the currently usedGregorian calendar. Thoseunaware, or unwilling, to accept thedate change werepranked.Others thinkthe holiday startedas a cheerful way to mark the start of spring.

When you see a panda at the zoo, it stands out against the green bamboo that it eats all day. But that setting is misleading. In the wild, the pandas black-and-white patches help it to blend in with its background. That keeps the animal camouflaged against predators like tigers, leopards and dholes, a type of wild dog, a new study finds.



We have been fooled into thinking that [pandas] are much easier to see than they are in the wild. If we want to understand animal coloration, we need to look at species where they live, says Tim Caro. Hes a zoologist at the University of Bristol in England. He is a co-author on the new study, which was published October 28 in Scientific Reports.



The giant panda (Ailuropoda melanoleuca), a rare species of bear, lives in remote mountain forests in southwest China. Earlier research had shown that pandas white patches help them blend into snowy areas. And their dark legs and shoulders match well with shady bits of forest. Or at least they do to human eyes.







We tend to usually overestimate how well animals can see because our own color perception is so good, says Ossi Nokelainen. He is an ecologist at the University of Jyvskyl in Finland.



For their new study, Nokelainen, Caro and their colleagues obtained 15 images of pandas in the wild. They then corrected the photos to match how domestic dogs and cats would see the images. Dogs and cats arent dholes and tigers, but their vision should be similar. And the images showed that the pandas should be well-camouflaged from their predators, at least from a distance.



This makes sense, says Nokelainen, since pandas have to stay in one place, fairly still, for a long time to eat enough bamboo. They can just evade the predators in a way that they cant be detected easily by the predators.







































JoAnna Wendel




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Savanna (noun, Suh-van-uh)



If you’ve ever seen The Lion King, you’ve seen a savanna. A savanna is a rolling grassland scattered with trees and shrubs. This type of ecosystem covers about 20 percent of the world’s land. That includes nearly half of Africa. The African savanna is home to lions, hyenas, zebras and other Lion King creatures. The Australian savanna hosts animals like kangaroos and wallabies. Savannas are also found in South America and Asia. And in North America, the oak savanna is one of the worlds most endangered ecosystems.



Most people may be familiar with the African savanna. But did you know North America has savannas, too? These grasslands are scattered with oak trees.Steepcone/Wikimedia Commons (CC BY-SA 3.0)



Most savannas don’t have the four seasons you might be familiar with. These areas alternate between dry winters and wet summers. During the winter, a savanna may not get rain for months at a time. That prevents many trees from growing there. Dry conditions also allow savannas to catch fire easily. Those fires prevent young trees from growing up and turning these habitats into forests. But heavy summer rains help thick grasses grow. That prevents the savanna from being a desert.



In a sentence



African savanna elephants are the largest land mammals in the world.



Check out the full list of Scientists Say.

Excess nutrients, such as nitrogen and phosphorus, can harm coastal ecosystems. In the past researchers have mostly focused on excess nutrients from farms, usually from fertilizer that runs off fields instead of sticking around in the soil. Now, a new model explores the global impact of nitrogen from sewage and finds that nutrients in our poop and pee are also causing harm.



Explainer: The fertilizing power of N and P



Coastal areas face dangers ranging from climate change to overfishing to pollution. And sewage may pile on to these problems. An influx of nutrients can lead to eutrophication. That process causes oxygen levels in the water to drop to low levels that can kill fish and other creatures.



Coral reefs and seagrass beds are important ecosystems that are home to many creatures. Researchers at the University of California, Santa Barbara wanted to explore which coastal areas receive the most nitrogen and determine the risks to these key ecosystems. So they created a computer model.





However, theres a lot scientists dont know about the flow of nutrients from sewage into the ocean. And what they do know isnt spread evenly around the world. For example, researchers have more data on nutrients from sewer systems. But many places lack sewers.





To get past that data shortage, the researchers looked at what people eat. Protein from food is a major source of nitrogen in wastewater. The scientists used protein consumption and population size and density to calculate how much nitrogen people excrete in various locations. They then accounted for how wastewater treatment removes nitrogen.



The researchers combined this data with a high-resolution map of watersheds worldwide. That showed where the nitrogen flows. Overall, wastewater dumps 6.2 teragrams (13.7 billion pounds) of nitrogen into the ocean, according to the model. Thats equal to about 40 percent of the nitrogen that comes from agriculture, the scientists report November 10 in Plos One.  



The new results suggest that 58 percent of coral reefs and 88 percent of seagrass beds receive wastewater nitrogen. And the model allows researchers to zoom in on specific areas. This could help guide conservation efforts, the authors suggest.




Coral reefs and seagrass under threat



These maps show where nitrogen may threaten coral reefs (A) and seagrass (B). (Use the arrows at left and right to switch between the images). They are based on a computer model that researchers developed. The model simulates how nitrogen gets into coastal environments. First, the model estimates how much nitrogen ends up in sewage based on what people eat and where they live. Then it adjusts the nitrogen levels in the sewage based on wastewater treatment. Finally, using a very detailed map of the worlds watersheds, the model simulates how the nitrogen flows out to sea. These maps take results from the model and label whether nitrogen concentrations are high (High wastewater impact) or low (No wastewater impact) at areas with corals (A) and seagrass (B). Click here to see both graphs in one image.



Tuholske et al/Plos One 2021 (CC BY 4.0)Tuholske et al/Plos One 2021 (CC BY 4.0)




Data dive:



Open up a visualization of the model here. Its easiest to see the nitrogen data when Dark mode is selected. Make sure theres a check mark next to Location Names and Nitrogen Plumes. Zoom in on the coastal area closest to where you live. What is the concentration of the nitrogen there?Can you find any places that receive 100,000,000 grams of nitrogen/year? (Hint: you may have to zoom in a lot.) How about 1,000,000,000 grams?Check the box next to Nitrogen Source. What do you notice about the places that light up?Look at Map A above. Some areas are hotspots for coral wastewater impact. These have lots of red dots clustered together. Where are these areas? What do they have in common?Where are corals less likely to experience risks from nitrogen?Look at Map B. What are hotspots for seagrass wastewater impact?Where is seagrass less likely to experience risks from nitrogen?

A newfound trove of fossils in South America offers a peek into dinosaur family life. All of them belonged to a species known as Mussaurus patagonicus (Muh-suh-SAW-us Pat-uh-GON-ih-kah). It was an early, smallish ancestor of huge, long-necked sauropods (SAHR-oh-pahdz). (Think Apatosaurus and the behemoth Dreadnoughtus schrani.) The jumble of fossilized eggs, nests and bones now suggest these creatures traveled in herds.



Clutches of eggs were found alongside the skeletons of dozens of newborn, juvenile and adult dinos. This mix suggests the creatures stayed together throughout their lives. Their herds would have roamed some 193 million years ago. Other types of dinos showed signs of herd-living. But the new fossils are at least 40 million years older than the previously oldest evidence of dinosaur herds. Researchers described the new find October 21 in Scientific Reports.



This fossilized egg dates to about 193 million years ago. It was found in dry southern Argentina. The site held bones from individuals of many ages as well as egg clutches. Together, they suggest these dinos traveled in herds.Roger Smith



Diego Pol is a paleontologist with the Museum of Paleontology Egidio Feruglio. Thats in Trelew, Argentina. He was part of a team that unearthed the new fossils in southern Argentina. They found 80 dinosaurs and more than 100 eggs.



Each nest held eight to 30 eggs. Pols group closely examined five of the nests. In each, the eggs lay in two or three layers within shallow trenches. The age of the herding animals ranged widely. A close review showed some skeletons turned up at least two adults and nine juveniles. At least 11 others were under a year old.





Explainer: The age of dinosaurs



Fossils of the first known dinosaurs date to around 245 million years ago. By about 201 million years ago, the Triassic Period was coming to an end. Sauropod ancestors, including Mussaurus, were among the most abundant plant eaters on land. Mussaurus roamed in whats now Patagonias deserts. During their era, this area was semi-dry. Nearby was a lake that may have flooded and sometimes evaporated. A sudden flood might explain this herds demise.



Mind-bogglingly massive sauropods didnt arise until the Jurassic Period. That came just after the Triassic. But fossils of Triassic relatives like Mussaurus were already showing evidence of a growth spurt. Bigger bodies would have needed more food. Those needs may have encouraged these creatures to work together. Forming herds would have helped them forage across long distances, the researchers suggest.

Modern-day rhinos,which weigh anywhere from 1,800 to5,100 pounds, are no lightweights. However, they pale in comparison totheir prehistoric cousinthat roamed China about 26million years ago.The massive mammal weighed 46,000 pounds almost as much as four largeAfricanelephants. Standing ata heightof23ft (7m), it was alsotaller than a giraffe.

A long string of galaxies appears to form an arc stretching more than 3 billion light-years across the distant universe. If the arc turns out to be real, it would challenge a basic idea about how the cosmos is structured. Its known as the cosmological principle. And it holds that no matter where you look in the universe, on large scales matter will be distributed fairly evenly.



If it now turns out that this is not true as the newfound arc suggests it would overturn cosmology as we know it, said Alexia Lopez on June 7. She spoke at a news conference at a virtual meeting of the American Astronomical Society. It would mean, she said, that our standard model, not to put it too heavily, kind of falls through.



As a cosmologist, Lopez studies the origins and evolution of the universe. She works at the University of Central Lancashire in Preston, England. She was part of a team that discovered the distant structure. They call it simply the Giant Arc.



Astronomers discovered what they say is a giant arc of galaxies (smile-shaped curve in the middle of this image) by using the light from distant quasars (blue dots) to map out where in the sky that light got absorbed by magnesium atoms in the halos (dark spots) that surround foreground galaxies.A. Lopez



The arc turned up as the researchers were studying images captured as part of the Sloan Digital Sky Survey. That survey, which covers about one-third of the sky, includes the most detailed three-dimensional maps of our universe. It includes light spectra for more than three million astronomical objects.



Lopezs team focused on light from some 40,000 quasars. These are the glowing cores of giant galaxies. Yet they are so distant they appear as mere points of light. On its way to Earth, some of that light gets absorbed by atoms in and around galaxies nearer to us. This absorption creates a signature change in the light that eventually reaches telescopes on Earth or in space.





The Giant Arcs signature is due to magnesium atoms. Each has lost one electron. Theyre glowing in the halos of galaxies about 9.2 billion light-years away. Quasar light absorbed by those atoms traces out a nearly symmetrical curve. That curve contains dozens of galaxies. Lopez reports that together they span about one-fifteenth the radius of the observable universe.



That arc is invisible to the human eye. But if you could see it from Earth, it would span about 20 times the width of the full moon.





See nearly 400,000 galaxies in this animation, which contains images of the actual galaxies in these positions (or sometimes their near cousins). It was made from data derived from release 7 of the Sloan Digital Sky Survey (SDSS). The animations come from Miguel Aragon and Alex Szalay of Johns Hopkins University and Mark Subbarao of Chicagos Adler Planetarium.



The arc as cosmic dilemma



The problem is that this arc makes part of the sky seem too organized. The galaxies are not as evenly distributed as astronomers have always thought they should be.



As such, this finding is a very fundamental test of the hypothesis that the universe is homogeneous on large scales, says Subir Sarkar. Hes an astrophysicist at the University of Oxford in England. Although he studies large-scale structures in the cosmos, he did not take part in the new work. If the Giant Arc is real, he says, this is a very big deal.



But not all researchers are convinced the arc is real. Our eye has a tendency to pick up patterns, Sarkar notes. For instance, he points out that some people have claimed to see Stephen Hawkings initials written in fluctuations of the background cosmic microwave radiation. This is the oldest light in the universe.





Lopez ran three mathematical tests to figure out the odds that galaxies would line up in a giant arc just by chance. All three suggest that the structure is real. One test surpassed physicists gold standard that the odds of it being a statistical fluke should be less than 0.00003 percent.



That sounds pretty good, but it may not be good enough, Sarkar says. Right now, he says, I would say the evidence is tantalizing, but not yet compelling. 



More observations may be needed to firmly support or refute the presence of a Giant Arc.



Explainer: Stars and their families



But if the Giant Arc is real, it would join a growing group of large-scale structures in the universe that, when taken together, break the standard model of cosmology. This model assumes that when you look at large enough volumes of space above about 1 billion light-years across matter will map out evenly. The Giant Arc, however, appears about three times as long as that threshold.



And its not the only such seeming anomaly. There are a number of other large structures in the sky. These include the Sloan Great Wall, the Giant Gamma-Ray Burst Ring and the Huge Large Quasar Group.



With one large-scale structure, that could just be a statistical fluke, Lopez says. Thats not the problem. All of [those big structures] combined is what makes the problem even bigger.

When is a parasite not a parasite? Answer: When it provides a benefit to its host. Consider some microbes long thought to bring only harm to coastal mussels. New research shows some may actually help their hosts survive dangerous heat waves.



Called cyanobacteria (Sy-AN-oh-bak-TEER-ee-uh), these bacteria bore into the mussels outer shells. Studies had shown this can weaken mussel shells, notes Katy Nicastro. Shes a marine biologist at Rhodes University in South Africa. Being infested with those microbes can slow a mussels growth and reproduction, too. It can even cause the shells to shed their dark outer coat. But lighter-colored shells absorb less sunlight. And that might keep their hosts from overheating on sunny days.





Nicastro and her teammates wanted to know just how much heat protection those microbes might offer. So they collected mussels in Europe. They retrieved them from a rocky shore in northern Portugal. Some mussels had shells infested with the microbes. These had large white patches. Non-infested mussels had normal dark shells.





The researchers first removed the mussels from their shells. Then they inserted temperature sensors inside those shells. They placed these robomussels at nine coastal sites across Europe. The most northerly sites were in the Orkney Islands, north of Scotland. The most southerly sites were in Portugal.



Up to a dozen robomussels were glued next to live mussels on rocks in the intertidal zone. Here, seawater would cover the shells at high tide. Low tide would expose them to the air and sun. The sensors showed the temperature could drop 8 degrees Celsius (14.4 degrees Fahrenheit) or more when the shells were submerged.



Those sensors took measurements every half hour from August 1 to September 13, 2017. In the end, the researchers had to ignore data from three sites where weather records were not available.



Trends for the other six sites were clear. When not underwater, dark-shelled robomussels warmed faster. Sensors inside the dark-shelled robomussels also reached a higher temperature than the lighter-shelled ones. The team described its work in the June Global Change Biology.



Shells whitened by microbial infestation (top left) help mussels stay cool on hot, sunny days. In the thermal image (bottom), reds and yellows represent hotter temperatures.K. Nicastro



These data suggested shell color could mean the difference between life and death for mussels. So for these microbe infestations, Nicastro says, Now we have to consider the balance between positive and negative effects. It appeared those microbes can sometimes help the mussels.



To test that, Nicastros team looked at death rates for mussels during three 2018 heat waves in France. More than 95 percent of the mussels dying during the heat waves had dark shells, studies showed. Dark-shelled mussels were likely between 1.67 and 4.77 C (3 and 8.6 F) warmer than those with lighter shells. This suggests light-shelled mussels were more likely to survive.



Shell-weakening microbes usually are not viewed as a good thing for mussels, says Christopher Harley. Hes a marine biologist at the University of British Columbia in Vancouver, Canada. But during heat emergencies, that can save [a mussels] life, he says.



Mussels may not seem to be important creatures, but they are, says Harley. At low tide, intertidal mussel beds provide a moist, cool habitat. Hundreds of different species live among them. This includes everything from hermit crabs and worms to sponges and sea cucumbers. Indeed, Harley says, Mussel beds are the apartment complex of the rocky shore.

Pollen (noun, PAH-len)



This is a mass of small grains released by seed plants. Each individual piece of pollen is called a pollen grain. Each grain contains a reproductive cell that corresponds to a sperm cell in an animal. A pollen grain can fertilize the egg cell of other plant of the same species, eventually forming a seed that can grow into another plant.



Unlike the sperm cells of animals, pollen cannot move on its own. So plants have evolved different ways to get their pollen to the egg cells of other plants. Some pollen is hidden in flowers that have delicious nectar. When insects, such as bees, or other animals slurp up the nectar, they end up coated in pollen. When those animals move on to the next flower, they take the pollen with them helping the plant in the process.





Other pollen is simply spread on gusts of wind no animals needed. Unfortunately, the tiny grains can get in our eyes and noses. This can make some peoples eyes water and their noses run. They arent sick. Theyre just trying to wash out all the pollen that has blown in their faces.



In a sentence



Scientists studied ancient pollen grains to show that a rainforest once grew in Antarctica.



Check out the full list of Scientists Say.

It looks like a steak. It cooks like a steak. And according to the scientists who made and ate it, the thick and juicy slab smells and tastes like a steak. A ribeye, specifically. But appearances can be deceiving. Unlike any steak found on a menu or store shelf today, this one didnt come from a slaughtered animal.



Scientists printed it earlier this year with a bioprinter. The machine is much like a standard 3-D printer. The difference: This type uses cells as a form of living ink.



Fashioning inks to print tissues



The technology involves the printing of actual living cells, explains biologist Neta Lavon. She helped develop the steak. Those cells are incubated, she says, to grow in a lab. By that she means theyre given nutrients and kept at a temperature that lets them keep growing. Using real cells this way, she says, is a real innovation over previous new meat products. This allows the printed product to acquire the texture and qualities of a real steak.





Lavon works at Aleph Farms, a company in Haifa, Israel. Her teams steak project grew out of a partnership between the company and scientists at TechnionIsrael Institute of Technology, which is in Rehovot. The ribeye is the latest addition to a growing list of meats grown in a lab instead of as part of some animal.



Researchers call these new meats cultivated or cultured. Interest in them has grown in recent years, partly because the technology shows they are possible. Advocates say that if meat can be printed, then no animal would need to lose its life to become human food.





But dont look for these products on the store shelves just yet. Making meat this way is much harder and therefore costs more than raising and killing an animal. The technology will require drastic reductions in cost before cultured meat will be widely available, says Kate Krueger. Shes a cell biologist in Cambridge, Mass., who started Helikon Consulting. Her business works with companies who want to grow animal-based foods from cells. 



One of the most expensive components, says Krueger, is the cell-growth medium. This mix of nutrients keeps the cells alive and dividing. The medium contains expensive ingredients called growth factors. Unless the cost of growth factors drops, says Krueger, cultured meat cant be produced at comparable prices to animal meat.



The road to slaughter-free meats



The ribeye joins a growing list of cultured meat products. It started in 2013. Back then, a physician and scientist named Mark Post debuted the worlds first burger made with lab-grown meat. Three years later, Memphis Meats, based in California, unveiled a cultured-meat meatball. In 2017, it debuted cultured duck and chicken meat. Aleph Farms entered the picture the next year with a thin-cut steak. Unlike its new ribeye, it was not 3-D-printed.



To date, none of these cultured-meat products is yet on sale in stores.



Explainer: What is 3-D printing?



The companies working on them use technology borrowed from tissue engineering. Scientists in this field study how to use real cells to build living tissues or organs that might help people.



At Aleph Farms, the process of building a ribeye begins with collecting pluripotent stem cells from a cow. Scientists then place these in a growth medium. This type of cell can produce more cells by dividing again and again. They are special because they can develop into almost any type of animal cell. For instance, Lavon notes, They can mature into the cell types that comprise meat, such as muscle.



The incubated cells will grow and reproduce. When there are enough, a bioprinter will use them as a living ink to build a printed steak. It lays the cells down one layer at a time. This printer also creates a network of tiny channels that mimic blood vessels, Lavon says. These channels let nutrients reach the living cells.



After printing, the product goes in what the company calls a tissue bioreactor. Here, the printed cells and channels grow to form a single system. The company hasnt yet shared how long it takes to print a ribeye from start to finish.



Lavon says the technology works, but cant yet print lots of ribeye steaks. She predicts that within two or three years, though, cultured ribeye steaks could reach supermarkets. The company plans to start selling its first product, that thin-cut steak, next year.



Like Krueger, Lavon says costs remain a challenge. In 2018, Aleph Farms reported that producing one serving of cultured steak cost $50. At that price, Lavon says, it cant compete with the real thing. But if scientists can find lower-cost methods, she says, then tissue engineering may stand a chance of giving beef without the moo.



This is one in a series presenting news on technology and innovation, made possible with generous support from the Lemelson Foundation.

When early humans arrived in Europe around 45,000 years ago, they found Neandertals already there. So they hooked up with them. Those hookups between Homo sapiens and Neandertals happened more often than scientists had been assumed. Thats the conclusion of two new studies.



Scientists Say: Neandertal



Scientists analyzed ancient DNA from a tooth and two bone fragments. They were the remains of three people unearthed in the Bacho Kiro Cave in Bulgaria. The bone bits had been radiocarbon dated. This process can determine the age of once-living tissue.



The bones owners lived 43,000 and 46,000 years ago. That makes them the oldest known human remains in Europe. Stone tools typical of late Stone Age humans were found in the same soil as the fossils. With the DNA still inside the bone remains, scientists showed that Neandertals contributed about 3 to 4 percent of the humans DNA.





All of the Bacho Kiro individuals had recent Neandertal ancestors, as few as five to seven generations back in their family trees, says Mateja Hajdinjak. She is an evolutionary geneticist. Thats someone who studies DNA to learn about human evolution. She works at the Francis Crick Institute in London, England.



Scientists Say: Hominid



A second study shows further evidence of ancient interbreeding. Scientists turned it up a nearly complete human skull in 1950. They found it in a cave in whats now the Czech Republic. A new analysis of its DNA shows it came from a female. Her DNA suggests she also lived around 45,000 years ago. And about 2 percent of her genes come from Neandertals, say Kay Prfer and his colleagues. Prfer is an evolutionary geneticist. He works at the Max Planck Institute for the Science of Human History in Jena, Germany.



These human fossils arent the first ones found with bits of Neandertal DNA. But they appear to be the oldest. These data show for the first time that distinct human populations reached Europe fewer than 50,000 years ago. Neandertals interbred with all the groups detected so far. Some of their genes live on today in our DNA. Hajdinjaks findings were published April 7 in Nature. Prfers findings appeared April 7 in Nature Ecology & Evolution.



Explainer: What are genes?



Neandertals went extinct around 40,000 years ago. But some of their genes live on in humans. Nearly 2 percent of the DNA, on average, in non-African people comes from Neandertal ancestors. Present-day Africans have about 0.5 percent Neandertal DNA.



The new studies also suggest that some early human entrants to Europe had a long-lasting impact on our DNA. Others hit genetic dead-ends. The Bacho Kiro people represent a newly identified group of ancient Europeans. They have genetic ties to present-day East Asians and Native Americans. But they arent linked to western Eurasians, Hajdinjaks group says. The Czech Republic womans line, on the other hand, ended about 40,000 years ago. People today have inherited no genes from her descendants.



It is remarkable that the Bacho Kiro finds could represent a population that was spreading 45,000 years ago, at least, from Bulgaria to China, says Carles Lalueza-Fox. Hes an evolutionary geneticist who works at the Institute of Evolutionary Biology. Its in Barcelona, Spain.





Other people who reached Europe thousands of years later were the ancestors of todays Europeans, Hajdinjak suggests. At Bacho Kiro Cave, for instance, there is DNA from another newly recovered human-bone fragment. It only dates to around 35,000 years ago the Stone Age. This newer bone displays different DNA than that of the caves earlier residents. This Stone Age person contributed genes mainly to Europeans and western Asians, Hajdinjak says.



By nearly 40,000 years ago, Neandertals were headed for extinction. This means that a fairly large number of incoming humans were breeding with a small number of Neandertals, Lalueza-Fox suspects.



More recently than 40,000 years ago, new human migrants into Europe would mate with the people already there. But those new people would have little or no Neandertal ancestry. Over time, they would have diluted Neandertal DNA from the human gene pool down to the small amounts that remain today, he says.

Sincelanding on Mars on February 18, 2021,NASA'sPerseverance rover has achieved numerous "firsts," including beaming audiosounds from the Red Planet's surface. It alsomadehistory asthefirst spacecraft to record sounds from another spacecraft the Ingenuity helicopter on another planet.

Geologists have long maintained that our Earth comprises four layers the crust, the mantle, the outer core, and, the deepest layer,theinner core. However, a team of scientists led by Jo Stephenson, a doctoral student in seismology at Australian National University in Canberra, now asserts thatour planet may be harboring a mysterious, fifth layer an"inner-inner" coreas well.