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Humanity’s Ancestors Nearly Died Out, Genetic Study Suggests

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The population crashed following climate change about 930,000 years ago, scientists concluded. Other experts aren’t convinced by the analysis.

No place on the planet has escaped the influence of Homo sapiens, from the rainforests cleared for farms to microplastic-laced deep oceans to climate-altered jet streams. Last November, the world population reached 8 billion.

But as omnipresent as humans may be today, a team of scientists now claims that our species came very close to never appearing at all.

Researchers in China have found evidence suggesting that 930,000 years ago, the ancestors of modern humans suffered a massive population crash. They point to a drastic change to the climate that occurred around that time as the cause.

Our ancestors remained at low numbers — fewer than 1,280 breeding individuals — during a period known as a bottleneck. It lasted for over 100,000 years before the population rebounded.

“About 98.7 percent of human ancestors were lost at the beginning of the bottleneck, thus threatening our ancestors with extinction,” the scientists wrote. Their study was published on Thursday in the journal Science.

If the research holds up, it will have provocative implications. It raises the possibility that a climate-driven bottleneck helped split early humans into two evolutionary lineages — one that eventually gave rise to Neanderthals, the other to modern humans.

But outside experts said they were skeptical of the novel statistical methods that the researchers used for the study. “It is a bit like inferring the size of a stone that falls into the middle of the large lake from only the ripples that arrive at the shore some minutes later,” said Stephan Schiffels, a population geneticist at Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

For decades now, scientists have reconstructed the history of our species by analyzing the genes of living people. The studies all take advantage of the same basic facts of our biology: every baby is born with dozens of new genetic mutations, and some of those mutations can be handed down over thousands or even millions of years.

By comparing genetic variations in DNA, scientists can trace people’s ancestry to ancient populations that lived in different parts of the world, moved around and interbred. They can even infer the size of those populations at different times in history.

These studies have gotten more sophisticated as DNA sequencing technology has grown more powerful. Today, scientists can compare the entire genomes of people from different populations.

Every human genome contains over 3 billion genetic letters of DNA, each of which has been passed down for thousands or millions of years — creating a vast record of our history. To read that history, researchers now use increasingly powerful computers that can carry out the vast numbers of calculations required for more realistic models of human evolution.

Haipeng Li, an evolutionary genomics researcher at Chinese Academy of Sciences in Shanghai, and his colleagues spent over a decade creating their own method for reconstructing evolution.

The researchers named the method FitCoal (short for Fast Infinitesimal Time Coalescent). FitCoal lets scientists cut up history into fine slices of time, allowing them to create a model of a million years of evolution divided into periods of months.

“It is a tool we created to figure out the history of different groups of living things, from humans to plants,” Dr. Li said.

At first he and his colleagues focused on animals like fruit flies. But once enough genetic data from our own species had been sequenced, they turned to the history of humans, comparing the genomes of 3,154 people from 50 populations around the world.

The researchers explored various models in order to find one that best explains today’s genetic diversity among humans. They ended up with a scenario that included a near-extinction event among our ancestors 930,000 years ago.

“We realized we had discovered something big about human history,” said Wangjie Hu, a computational biologist at the Icahn School of Medicine at Mount Sinai in New York and an author of the study.

Before the bottleneck, the scientists concluded, the population of our ancestors included about 98,000 breeding individuals. It then shrank to fewer than 1,280 and stayed that small for 117,000 years. Then the population rebounded.

Dr. Hu and his colleagues argue in their paper that this bottleneck is consistent with the fossil record of our human ancestors.

Our branch of the evolutionary tree split from that of other apes about seven million years ago in Africa. Our ancestors had evolved to be tall and big-brained in Africa by about a million years ago. Afterward, some of those early humans spread out to Europe and Asia, evolving into Neanderthals and their cousins, the Denisovans.

Our own lineage continued to evolve into modern humans in Africa.

After decades of fossil hunting, the record of ancient human relatives remains relatively scarce in Africa in the period between 950,000 and 650,000 years ago. The new study offers a potential explanation: there just weren’t enough people to leave behind many remains, Dr. Hu said.

Brenna Henn, a geneticist at the University of California, Davis, who was not involved in the new study, said that a bottleneck was “one plausible interpretation.” But today’s genetic diversity might have been produced by a different evolutionary history, she added.

For example, humans might have diverged into separate populations then come together again. “It would be more powerful to test alternative models,” Dr. Henn said.

Dr. Hu and his colleagues propose that a global climate shift produced the population crash 930,000 years ago. They point to geological evidence that the planet became colder and drier right around the time of their proposed bottleneck. Those conditions may have made it harder for our human ancestors to find food.

But Nick Ashton, an archaeologist at the British Museum, noted that a number of remains of ancient human relatives dating to the time of the bottleneck have been found outside Africa.

If a worldwide disaster caused the human population in Africa to collapse, he said, then it should have made human relatives rarer elsewhere in the world.

“The number of sites in Africa and Eurasia that date to this period suggests that it only affected a limited population, who may have been ancestors of modern humans,” he said.

Dr. Li and his colleagues also drew attention to the fact that modern humans appear to have split from Neanderthals and Denisovans after their proposed population crash. They speculate that the two events are related.

The researchers noted that most apes have 24 pairs of chromosomes. Humans have only 23, thanks to the fusion of two sets. After the crash, the scientists suggest, a fused set of chromosomes may have arisen and spread through the tiny population.

“All humans with 24 pairs of chromosomes became extinct, while only the small isolated population with 23 pairs of chromosomes fortunately survived and passed down from generation to generation,” said Ziqian Hao, a bioinformatics researcher at Shandong First Medical University and an author of the study.

But Dr. Schiffels isn’t buying the story of the bottleneck quite yet: “The finding is very surprising indeed, and I think the more surprising the claim, the better the evidence should be.”

 

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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