Science

Tooth of an Ancient Girl Fills Gap in Human Family Tree

Published

3 years ago

May 17, 2022

Tooth of an Ancient Girl Fills Gap in Human Family Tree

A tooth discovered inside a mountain collapse Laos has solved one of many largest scientific mysteries of the Denisovans, a department of historic people that disappeared roughly 50,000 years in the past.

Since 2010, when Denisovan tooth and finger bones have been first found, DNA testing has revealed that the enigmatic hominins have been among the many ancestors of individuals alive at present in Australia and the Pacific.

However scientists didn’t perceive how the Denisovans, whose scant stays had been discovered solely in Siberia and Tibet, would have been capable of interbreed with the group of people who expanded east from Africa via Southeast Asia earlier than reaching Australia, New Guinea and different islands within the Pacific.

Now, the invention of a lady’s molar in Laos, revealed on Tuesday within the journal Nature Communications, places Denisovans proper within the path of recent people who arrived in Southeast Asia tens of hundreds of years later.

“We knew that Denisovans must be right here,” stated Laura Shackelford, a paleoanthropologist on the College of Illinois and a co-author of the brand new examine. “It’s good to have some tangible proof of their existence on this space.”

Dr. Shackelford joined a crew of French and Laotian colleagues on an expedition to the Annamite Mountains in northern Laos in 2008, and so they have been digging up fossils ever since. In one of many many caves that riddle the mountains, they’ve unearthed human cranium fragments courting again about 75,000 years, making them the oldest proof of recent people in Southeast Asia.

On the finish of the researchers’ 2018 subject season, kids from a close-by village advised Dr. Shackelford and her colleagues of one other cave that contained bones. Her Laotian colleagues warned her that the cave was a favourite spot for cobras, however she determined a visit inside was definitely worth the danger.

A crew of caving consultants scouted the location first, after which Dr. Shackelford made her manner right into a closet-sized cavity the place the youngsters claimed to have discovered bones. When she inspected the cave flooring, she noticed nothing.

“However then I turned my flashlight on, and I appeared up,” she recalled. “All you can see have been bones and tooth, embedded within the partitions and within the ceiling of this cave. They have been simply kind of all over the place.”

Dr. Shackelford and her colleagues began working full-time within the new cave, which they dubbed Cobra Cave ( regardless of by no means encountering a snake). They chiseled rocks the dimensions of soccer balls out of the partitions and soaked them in a gentle acid. The rock step by step disintegrated, leaving the more durable fossils behind.

On shut inspection, a lot of the fossils turned out to be bones from extinct mammals, comparable to pigs, deer and pygmy elephants. Gnaw marks on the bones revealed how all of them ended up in a jumble in Cobra Cave: Porcupines doubtless carried them there and chewed on the bones to hone their tooth.

Sorting via the gnawed bones, the scientists discovered a shock: a molar that resembled a human little one’s tooth. However some options of the molar instructed it was not fairly human. “We have been so amazed and so excited,” Dr. Shackelford stated.

They have been much more delighted when geologists examined the cave wall to find out the age of the tooth. The tooth itself was too small to investigate, however the researchers discovered fossils and minerals close by that contained radioactive parts that broke down at a daily tempo. By measuring these parts, the researchers estimated the tooth was between 164,000 and 131,000 years previous.

In different phrases, the Cobra Cave tooth is about twice as previous because the oldest trendy people that Dr. Shackelford and her colleagues have discovered within the area. The tooth’s nice age hinted that it belonged to an extinct relative of recent people. However which one?

Humanity’s lineage break up from the ancestors of chimpanzees about six million years in the past in Africa. Over the subsequent 4 million years, they developed into upright, big-brained meat-eaters. At that time, some family members started transferring to Europe and Asia from Africa. One species, known as Homo erectus, unfold east so far as Indonesia.

Proof from fossils and historic DNA point out that one other wave of early people traveled out of Africa even later. Because the inhabitants unfold throughout Europe and Asia, it break up about half 1,000,000 years in the past. The western inhabitants turned Neanderthals, and the japanese one turned Denisovans.

Paleoanthropologists first found Neanderthal fossils within the mid-1800s in Germany and Belgium and have since discovered an abundance of bones marking the group’s vary throughout Europe, the Center East and Siberia. The fossils revealed Neanderthals as stocky, chinless people. Instruments and different stays provided glimpses into their minds: They have been adept hunters who might stalk each rhinos and dolphins. They buried their lifeless and usual necklaces from eagle talons.

DNA in Neanderthal fossils additionally linked them to residing people. Quickly after trendy human ancestors moved out of Africa, they encountered Neanderthals within the Center East and interbred with them — most likely on a number of events.

Scientists have had a a lot more durable time reconstructing the traditional migration of the Denisovans. For years, the one place the place they fond these historic people was the Denisova Collapse Siberia. It was laborious to see how folks a number of thousand miles away, in Australia, New Guinea and close by islands, might have ended up with Denisovan DNA.

The Denisovan samples from Siberia have been restricted to a couple tooth and finger bones. Fortuitously, scientists discovered an abundance of DNA in these specimens, and even extracted Denisovan DNA from filth on the cave flooring.

The proof gathered to this point signifies that Denisovans occupied the cave 300,000 years in the past and inhabited the encircling space on and off till about 50,000 years in the past. In addition they seem to have left behind stone instruments within the cave.

On condition that Denisovans endured for tons of of hundreds of years, scientists have been assured that they’d discover Denisovan fossils elsewhere. In 2019, that proved to be the case. Chinese language researchers introduced the invention of a 160,000-year-old jaw in a Tibetan cave with tooth matching these discovered on the Siberian web site. That discovery in Tibet, greater than 1,400 miles south of Siberia, drastically expanded the identified vary of Denisovans.

The jaw additionally offered just a few extra clues concerning the Denisovans themselves. For one factor, the proportions of the jaw and tooth implied they may have been tall and solidly constructed, like soccer gamers. To outlive within the harsh surroundings of the Tibetan plateau, they’d have needed to stand up to low oxygen within the air and chilly climate.

Nonetheless, some 1,100 miles would have separated Denisovans in Tibet from trendy human ancestors in Southeast Asia, leaving scientists to surprise how the 2 teams might have interbred.

Inspecting the tooth from the Cobra Collapse Laos, Dr. Shackelford and her colleagues didn’t know if it had come from Denisovans, Neanderthals, Homo erectus or another unknown species of human. Over the previous 4 years, they’ve been analyzing the tooth for clues.

Initially, they hoped that it will include historic DNA. However earlier than destroying a part of the tooth to seek out out, they’d colleagues on the College of Copenhagen take a look at different mammal fossils discovered from the identical pattern of the Cobra Cave wall. These specimens yielded no DNA, in order that they determined to not search for any in it.

However they’d higher luck once they looked for protein fragments within the molar’s enamel. The chemical make-up of the fragments has solely been discovered within the tooth of recent people, Neanderthals and Denisovans — however not these of different mammals.

Sadly, the protein composition is identical in all three teams of hominins, leaving the researchers unable to say which one the molar got here from.

However the enamel of the juvenile tooth had yet one more piece of knowledge to supply: It belonged to a lady. It lacked a particular enamel protein encoded by a gene on the Y chromosome, which is simply carried by males.

The scientists made a high-resolution scan of the molar’s floor and inside, permitting them to check its high-quality anatomical construction to greater than 400 molars from residing and extinct people. Of these tooth, the Cobra Cave specimen most intently resembled a molar lodged within the Denisovan jaw from Tibet.

Shara Bailey, a paleoanthropologist at New York College who has studied the Tibetan jaw however was not concerned within the new examine, stated this conclusion was sound. “I agree one hundred pc with the evaluation,” she stated.

Dr. Bailey acknowledged that some folks could surprise how a single tooth might reveal a lot about its Paleolithic proprietor. However the cusps and ridges of tooth are advanced landscapes, and the form of these panorama is essentially decided by genes, making tooth a wealthy trove of details about evolution.

“Enamel are the unsung heroes of paleoanthropology,” Dr. Bailey stated.

The invention of Denisovans in Laos reveals that they have been precisely the place they wanted to be to interbreed with trendy people who arrived in Southeast Asia hundreds of years later.

Dr. Bailey and Dr. Shackelford agreed that extra Denisovan fossils wait to be found elsewhere. Latest research have discovered a small quantity of Denisovan DNA in East Asians, for instance, which their ancestors could have acquired via a separate interbreeding. And a few historic tooth that have been already found in China and Taiwan appear now like they may have a Denisovan form, warranting a contemporary look.

However Bence Viola, a paleoanthropologist on the College of Toronto who was not concerned within the examine, stated the Cobra Cave tooth itself offered some contemporary clues concerning the Denisovans.

“These guys have been capable of take care of in depth snow cowl and really low winter temperatures however on the identical time with humid tropical environments,” he stated. “Denisovans have been very adaptable — doubtless extra so than Neanderthals. They have been most just like trendy people ultimately.”

Science

Pink Fire Retardant, a Dramatic Wildfire Weapon, Poses Its Own Dangers

Published

3 hours ago

January 10, 2025

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Pink Fire Retardant, a Dramatic Wildfire Weapon, Poses Its Own Dangers

From above the raging flames, these planes can unleash immense tankfuls of bright pink fire retardant in just 20 seconds. They have long been considered vital in the battle against wildfires.

But emerging research has shown that the millions of gallons of retardant sprayed on the landscape to tame wildfires each year come with a toxic burden, because they contain heavy metals and other chemicals that are harmful to human health and the environment.

The toxicity presents a stark dilemma. These tankers and their cargo are a powerful tool for taming deadly blazes. Yet as wildfires intensify and become more frequent in an era of climate change, firefighters are using them more often, and in the process releasing more harmful chemicals into the environment.

Some environmental groups have questioned the retardants’ effectiveness and potential for harm. The efficiency of fire retardant has been hard to measure, because it’s one of a barrage of firefighting tactics deployed in a major fire. After the flames are doused, it’s difficult to assign credit.

The frequency and severity of wildfires has grown in recent years, particularly in the western United States. Scientists have also found that fires across the region have become faster moving in recent decades.

There are also the longer-term health effects of exposure to wildfire smoke, which can penetrate the lungs and heart, causing disease. A recent global survey of the health effects of air pollution caused by wildfires found that in the United States, exposure to wildfire smoke had increased by 77 percent since 2002. Globally, wildfire smoke has been estimated to be responsible for up to 675,000 premature deaths per year.

Fire retardants add to those health and environmental burdens because they present “a really, really thorny trade-off,” said Daniel McCurry, an assistant professor of civil and environmental engineering at the University of Southern California, who led the recent research on their heavy-metal content.

The United States Forest Service said on Thursday that nine large retardant-spraying planes, as well as 20 water-dropping helicopters, were being deployed to fight the Southern California fires, which have displaced tens of thousands of people. Several “water scooper” amphibious planes, capable of skimming the surface of the sea or other body of water to fill their tanks, are also being used.

Two large DC-10 aircraft, dubbed “Very Large Airtankers” and capable of delivering up to 9,400 gallons of retardant, were also set to join the fleet imminently, said Stanton Florea, a spokesman for the National Interagency Fire Center in Boise, Idaho, which coordinates national wildland firefighting efforts across the West.

Sprayed ahead of the fire, the retardants coat vegetation and prevent oxygen from allowing it to burn, Mr. Florea said. (Red dye is added so firefighters can see the retardant against the landscape.) And the retardant, typically made of salts like ammonium polyphosphate, “lasts longer. It doesn’t evaporate, like dropping water,” he said.

The new research from Dr. McCurry and his colleagues found, however, that at least four different types of heavy metals in a common type of retardant used by firefighters exceeded California’s requirements for hazardous waste.

Federal data shows that more than 440 million gallons of retardant were applied to federal, state, and private land between 2009 and 2021. Using that figure, the researchers estimated that between 2009 and 2021, more than 400 tons of heavy metals were released into the environment from fire suppression, a third of that in Southern California.

Both the federal government and the retardant’s manufacturer, Perimeter Solutions, have disputed that analysis, saying the researchers had evaluated a different version of the retardant. Dan Green, a spokesman for Perimeter, said retardants used for aerial firefighting had passed “extensive testing to confirm they meet strict standards for aquatic and mammalian safety.”

Still, the findings help explain why concentrations of heavy metals tend to surge in rivers and streams after wildfires, sometimes by hundreds of times. And as scrutiny of fire suppressants has grown, the Forestry Service has set buffer zones surrounding lakes and rivers, though its own data shows retardant still inadvertently drifts into those waters.

In 2022, the environmental nonprofit Forest Service Employees for Environmental Ethics sued the government in federal court in Montana, demanding that the Forest Service obtain a permit under the Clean Water Act to cover accidental spraying into waterways.

The judge ruled that the agency did indeed need to obtain a permit. But it allowed retardant use to continue to protect lives and property.

Science

2024 Brought the World to a Dangerous Warming Threshold. Now What?

Published

12 hours ago

January 10, 2025

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2024 Brought the World to a Dangerous Warming Threshold. Now What?

Source: Copernicus/ECMWF

Note: Temperature anomalies relative to 1850-1900 averages.

At the stroke of midnight on Dec. 31, Earth finished up its hottest year in recorded history, scientists said on Friday. The previous hottest year was 2023. And the next one will be upon us before long: By continuing to burn huge amounts of coal, oil and gas, humankind has all but guaranteed it.

The planet’s record-high average temperature last year reflected the weekslong, 104-degree-Fahrenheit spring heat waves that shuttered schools in Bangladesh and India. It reflected the effects of the bathtub-warm ocean waters that supercharged hurricanes in the Gulf of Mexico and cyclones in the Philippines. And it reflected the roasting summer and fall conditions that primed Los Angeles this week for the most destructive wildfires in its history.

“We are facing a very new climate and new challenges, challenges that our society is not prepared for,” said Carlo Buontempo, director of the Copernicus Climate Change Service, the European Union monitoring agency.

But even within this progression of warmer years and ever-intensifying risks to homes, communities and the environment, 2024 stood out in another unwelcome way. According to Copernicus, it was the first year in which global temperatures averaged more than 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, above those the planet experienced at the start of the industrial age.

For the past decade, the world has sought to avoid crossing this dangerous threshold. Nations enshrined the goal in the 2015 Paris agreement to fight climate change. “Keep 1.5 alive” was the mantra at United Nations summits.

Yet here we are. Global temperatures will fluctuate somewhat, as they always do, which is why scientists often look at warming averaged over longer periods, not just a single year.

But even by that standard, staying below 1.5 degrees looks increasingly unattainable, according to researchers who have run the numbers. Globally, despite hundreds of billions of dollars invested in clean-energy technologies, carbon dioxide emissions hit a record in 2024 and show no signs of dropping.

One recent study published in the journal Nature concluded that the absolute best humanity can now hope for is around 1.6 degrees of warming. To achieve it, nations would need to start slashing emissions at a pace that would strain political, social and economic feasibility.

But what if we’d started earlier?

By spewing heat-trapping gases into the atmosphere, humankind has lifted global temperatures to record highs.

If nations had started reducing emissions in 2005, they could have made gradual cuts to limit warming to 1.5 degrees.

Starting in 2015, when the Paris agreement was adopted, would have required steeper cuts.

Starting today would require cuts so drastic as to appear essentially impossible.

“It was guaranteed we’d get to this point where the gap between reality and the trajectory we needed for 1.5 degrees was so big it was ridiculous,” said David Victor, a professor of public policy at the University of California, San Diego.

The question now is what, if anything, should replace 1.5 as a lodestar for nations’ climate aspirations.

“These top-level goals are at best a compass,” Dr. Victor said. “They’re a reminder that if we don’t do more, we’re in for significant climate impacts.”

The 1.5-degree threshold was never the difference between safety and ruin, between hope and despair. It was a number negotiated by governments trying to answer a big question: What’s the highest global temperature increase — and the associated level of dangers, whether heat waves or wildfires or melting glaciers — that our societies should strive to avoid?

The result, as codified in the Paris agreement, was that nations would aspire to hold warming to “well below” 2 degrees Celsius while “pursuing efforts” to limit it to 1.5 degrees.

Even at the time, some experts called the latter goal unrealistic, because it required such deep and rapid emissions cuts. Still, the United States, the European Union and other governments adopted it as a guidepost for climate policy.

Christoph Bertram, an associate research professor at the University of Maryland’s Center for Global Sustainability, said the urgency of the 1.5 target spurred companies of all kinds — automakers, cement manufacturers, electric utilities — to start thinking hard about what it would mean to zero out their emissions by midcentury. “I do think that has led to some serious action,” Dr. Bertram said.

But the high aspiration of the 1.5 target also exposed deep fault lines among nations.

China and India never backed the goal, since it required them to curb their use of coal, gas and oil at a pace they said would hamstring their development. Rich countries that were struggling to cut their own emissions began choking off funding in the developing world for fossil-fuel projects that were economically beneficial. Some low-income countries felt it was deeply unfair to ask them to sacrifice for the climate given that it was wealthy nations — and not them — that had produced most of the greenhouse gases now warming the world.

“The 1.5-degree target has created a lot of tension between rich and poor countries,” said Vijaya Ramachandran, director for energy and development at the Breakthrough Institute, an environmental research organization.

Costa Samaras, an environmental-engineering professor at Carnegie Mellon University, compared the warming goals to health officials’ guidelines on, say, cholesterol. “We don’t set health targets on what’s realistic or what’s possible,” Dr. Samaras said. “We say, ‘This is what’s good for you. This is how you’re going to not get sick.’”

“If we were going to say, ‘Well, 1.5 is likely out of the question, let’s put it to 1.75,’ it gives people a false sense of assurance that 1.5 was not that important,” said Dr. Samaras, who helped shape U.S. climate policy from 2021 to 2024 in the White House Office of Science and Technology Policy. “It’s hugely important.”

Scientists convened by the United Nations have concluded that restricting warming to 1.5 degrees instead of 2 would spare tens of millions of people from being exposed to life-threatening heat waves, water shortages and coastal flooding. It might mean the difference between a world that has coral reefs and Arctic sea ice in the summer, and one that doesn’t.

Each tiny increment of additional warming, whether it’s 1.6 degrees versus 1.5, or 1.7 versus 1.6, increases the risks. “Even if the world overshoots 1.5 degrees, and the chances of this happening are increasing every day, we must keep striving” to bring emissions to zero as soon as possible, said Inger Anderson, the executive director of the United Nations Environment Program.

Officially, the sun has not yet set on the 1.5 target. The Paris agreement remains in force, even as President-elect Donald J. Trump vows to withdraw the United States from it for a second time. At U.N. climate negotiations, talk of 1.5 has become more muted compared with years past. But it has hardly gone away.

“With appropriate measures, 1.5 Celsius is still achievable,” Cedric Schuster, the minister of natural resources and environment for the Pacific island nation of Samoa, said at last year’s summit in Azerbaijan. Countries should “rise to the occasion with new, highly ambitious” policies, he said.

To Dr. Victor of U.C. San Diego, it is strange but all too predictable that governments keep speaking this way about what appears to be an unachievable aim. “No major political leader who wants to be taken seriously on climate wants to stick their neck out and say, ‘1.5 degrees isn’t feasible. Let’s talk about more realistic goals,’” he said.

Still, the world will eventually need to have that discussion, Dr. Victor said. And it’s unclear how it will go.

“It could be constructive, where we start asking, ‘How much warming are we really in for? And how do we deal with that?’” he said. “Or it could look very toxic, with a bunch of political finger pointing.”

Methodology

The second chart shows pathways for reducing carbon emissions that would have a 66 percent chance of limiting global warming this century to 1.5 degrees Celsius above the preindustrial average.

Science

U.S. Efforts to Cut Emissions Stalled in 2024 as Power Demand Surged

Published

20 hours ago

January 9, 2025

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U.S. Efforts to Cut Emissions Stalled in 2024 as Power Demand Surged

America’s efforts to cut its climate change pollution stalled in 2024, with greenhouse gas emissions dropping just a fraction, 0.2 percent, compared to the year before, according to estimates published Thursday by the Rhodium Group, a research firm.

Despite continued rapid growth in solar and wind power, emissions levels stayed relatively flat last year because demand for electricity surged nationwide, which led to a spike in the amount of natural gas burned by power plants.

The fact that emissions didn’t decline much means the United States is even further off-track from hitting President Biden’s goal of slashing greenhouse gases 50 percent below 2005 levels by 2030. Scientists say all major economies would have to cut their emissions deeply this decade to keep global warming at relatively low levels.

Since 2005, United States emissions have fallen roughly 20 percent, a significant drop at a time when the economy has also expanded. But to meet its climate goals, U.S. emissions would need to decline nearly 10 times as fast each year as they’ve fallen over the past decade. That seems increasingly unlikely, experts say, especially since President-elect Donald J. Trump has promised to dismantle Mr. Biden’s climate policies and promote the production of fossil fuels, the burning of which generates greenhouse gases.

“On the one hand, it is notable that we’ve now seen two years in a row where the U.S. economy grew but emissions went down,” said Ben King, an associate director at the Rhodium Group. “But it’s far from enough to achieve our climate targets.”

The biggest reason that U.S. emissions have fallen in recent years is that electric utilities have been retiring their older, dirtier coal-fired power plants and replacing them with cheaper and less-polluting natural gas, wind and solar power. That trend mostly continued last year, with a few unexpected ups and downs.

The nation’s demand for electricity, which has stayed more or less flat for two decades, suddenly jumped by roughly 3 percent in 2024, in large part because scorching heat during the summer caused many Americans to crank up their air-conditioners. A smaller factor was that tech companies have been building more energy-hungry data centers in states like Virginia and Texas.

While power companies installed large numbers of wind turbines, solar panels and batteries last year to meet rising demand, natural gas use also rose to record highs, while coal use declined only slightly. The net result was that emissions from the power sector increased an estimated 0.2 percent, according to the Rhodium Group.

At the same time, transportation, the nation’s largest source of greenhouse gases, saw an 0.8 percent rise in emissions last year. Gasoline and jet fuel consumption both increased as Americans continued to drive and fly more after the pandemic. Nearly 10 percent of new car sales in 2024 were less-polluting electric vehicles, but those models still make up a small fraction of total cars on the road and have yet to put a major dent in transportation emissions.

On the flip side, emissions from America’s industrial sector — which includes steel, cement and chemicals — fell by 1.8 percent in 2024. Some of that may have been the result of lost output, as two hurricanes and a strike at the nation’s ports disrupted some factory activity in the fall, Mr. King said.

“It’s a reminder that there’s always some bumpiness in emissions,” Mr. King said. “It’s not just a question of how many electric vehicles are on the road or how much solar we’ve installed. A big portion of our economy still relies on fossil fuels.”

One of the most striking findings in this year’s data was that emissions from oil and gas operations dropped roughly 3.7 percent in 2024. Even though the United States produced record amounts of oil and near-record amounts of natural gas last year, many companies appear to have curbed leaks of methane, which is the main ingredient in natural gas and which can seep into the atmosphere and contribute significantly to global warming.

Over the past few years, the Biden administration and several states have adopted new regulations that require oil and gas producers to detect and fix methane leaks. Many companies also have financial incentives to capture methane to sell rather than vent it into the air.

Between 2014 and 2024, U.S. companies appear to have reduced the amount of methane that escaped, per each cubic feet of gas they produced, by 40 percent, according to the Rhodium Group.

Several experts have estimated that greenhouse gases generated in the United States could start dropping sharply in the years ahead if many clean energy policies stay in place, particularly the 2022 Inflation Reduction Act that pumped hundreds of billions of dollars into low-carbon energy technologies such as electric vehicles, wind turbines, solar panels, nuclear reactors, green hydrogen and batteries.

While Mr. Trump has pledged to scrap many of Mr. Biden’s subsidies and tax credits for electric vehicles and low-carbon energy, it remains to be seen whether Congress will agree.

That law has not yet had a major impact on the country’s emissions, said Mr. King, since it takes time for new factories to open and power plants to get built. But, he said, data shows that low-carbon energy and transportation now make up fully 5 percent of total U.S. private investment.

“That’s a leading indicator that things are changing quickly,” he said.