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Crossing From Asia, the First Americans Rushed Into the Unknown

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Crossing From Asia, the First Americans Rushed Into the Unknown

Three new genetic analyses lend detail, and mystery, to the migration of prehistoric humans throughout the Western Hemisphere.

Image
Excavation of a skeleton approximately 9,600 years old in a rock shelter in Brazil. New DNA analyses show the earliest known Americans split into distinct groups after they crossed a land bridge from Asia.CreditCreditAndré Strauss

Nearly 11,000 years ago, a man died in what is now Nevada. Wrapped in a rabbit-skin blanket and reed mats, he was buried in a place called Spirit Cave.

Now scientists have recovered and analyzed his DNA, along with that of 70 other ancient people whose remains were discovered throughout the Americas. The findings lend astonishing detail to a story once lost to prehistory: how and when humans spread across the Western Hemisphere.

The earliest known arrivals from Asia were already splitting into recognizably distinct groups, the research suggests. Some of these populations thrived, becoming the ancestors of indigenous peoples throughout the hemisphere.

But other groups died out entirely, leaving no trace save for what can be discerned in ancient DNA. Indeed, the new genetic research hints at many dramatic chapters in the peopling of the Americas that archaeology has yet to uncover.

“Now, this is the grist for archaeologists,” said Ben Potter of the University of Alaska, who was not involved in the new papers. “Holy cow, this is awesome.”

Earlier studies had indicated that people moved into the Americas at the end of the last ice age, traveling from Siberia to Alaska across a land bridge now under the Bering Sea. They spread southward, eventually reaching the tip of South America.

Until recently, geneticists could offer little insight into these vast migrations. Five years ago, just one ancient human genome had been recovered in the Western Hemisphere: that of a 4,000-year-old man discovered in Greenland.

The latest batch of analyses, published in three separate studies, marks a turnaround. In the past few years, researchers have recovered the genomes of 229 ancient people from teeth and bones discovered throughout the Americas.




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Northern

branch

About 16,000 years ago, the ancestors of living indigenous Americans split into two main branches.

NORTH

AMERICA

Ancient Montana boy

Around 14,000 years ago, the southern branch split into new branches that rapidly spread into South America.

Spirit Cave

Southern

branch

Starting 9,000 years ago, a wave of people from North or Central America replaced older populations in South America.

By at least 4,200 years ago,

a group of people related to ancient Californians had become widespread in the Central Andes.

SOUTH

AMERICA

Waves of Americans

Analysis of ancient DNA suggests that a small population of people from Siberia populated the Americas. Over thousands of years, different branches expanded southward, mixing with or replacing earlier waves.

David Reich of Harvard and his colleagues found evidence for the waves shown above. Other teams have come to broadly similar conclusions, though many questions remain.

Waves of Americans

Analysis of ancient DNA suggests that a small population of people from Siberia populated the Americas. Over thousands of years, different branches expanded southward, mixing with or replacing earlier waves.

David Reich of Harvard and his colleagues found evidence for the waves shown below. Other teams have come to broadly similar conclusions, though many questions remain.

Northern

branch

Southern

branch

NORTH

AMERICA

Ancient Montana boy

Spirit Cave

About 16,000 years ago, the ancestors of living indigenous Americans split into two main branches.

About 14,000 years ago, the southern branch split into new branches that rapidly spread into South America.

Starting 9,000 years ago, a wave of people from North or Central America replaced older populations in South America.

SOUTH

AMERICA

By at least 4,200 years ago, a group of people related to ancient Californians had become widespread in the Central Andes.


By The New York Times | Source: Cosimo Posth et al., Cell

The first, described in January by Eske Willerslev, a geneticist at the University of Copenhagen, was an 11,500-year-old girl whose remains were found in eastern Alaska.

The second was discovered hundreds of miles away, in western Alaska, and lived 9,000 years ago, Dr. Willerslev and his colleagues reported on Thursday in the journal Science.

The Ancient Beringians separated from the ancestors of living indigenous people in the Americas about 20,000 years ago. The new findings suggest they endured for several thousand years. Then they disappeared, leaving no known genetic trace in living people.

But another wave of migrants from Siberia did not stop in Alaska. They kept moving, eventually arriving south of the ice age glaciers. Then they split into two branches.

One group turned and headed north, following the retreating glaciers into Canada and back to Alaska. The other branch took a remarkable journey south.

The genetic data suggest that this group spread swiftly across much of North America and South America about 14,000 years ago. The expansion may have taken only centuries.

“It’s basically an explosion,” Dr. Willerslev said.

The man from Spirit Cave in Nevada belonged to this so-called southern branch of migrants. He also was closely related to a 12,700-year-old boy found on the other side of the Rocky Mountains in Montana, Dr. Willerslev also found.

Image
Eske Willerslev, center, with members of the Fallon Paiute-Shoshone tribe in Nevada. With permission from the tribe, Dr. Willerslev was able to retrieve DNA from a tooth belonging to the Spirit Cave man.CreditLinus Mørk, Magus Film

But the man from Spirit Cave also turned out to have a close genetic link to 10,400-year-old skeletons found in Brazil, on the other side of the Equator.

David Reich of Harvard University and his colleagues found a similar pattern in their own research, published on Thursday in the journal Cell.

They uncovered a link between the ancient Montana boy and another group of ancient South Americans, including a 10,900-year-old skeleton in Chile. Like Dr. Willerslev’s work, the kinship suggests that migrants moved quickly from North America to South America.

“We agree that this must be a rapid radiation,” said Dr. Reich.

Starting about 9,000 years ago, both teams found, additional waves of people moved southward. Dr. Willerslev’s research suggests the new arrivals mixed with older South American populations.

Dr. Reich, on the other hand, sees evidence for two waves of migrants who completely replaced the people who had lived in South America.

[Like the Science Times page on Facebook. | Sign up for the Science Times newsletter.]

The new research also revealed instances of remarkable continuity, kinships that spanned thousands of years.

Dr. Willerslev and his colleagues compared the genome of the man from Spirit Cave to those of four sets of remains found nearby in Nevada’s Lovelock Cave, who lived as recently as 600 years ago.

All of these people were closely related, his team found, despite being separated by 10,000 years of history.

A similar bond was found in the Andes. John Lindo of Emory University and his colleagues analyzed DNA from seven people who lived at high elevations between 6,800 and 1,400 years ago.

The researchers estimate that people who lived above 7,500 feet in the mountains were separated from the lowland populations between 9,200 and 8,200 years ago. Today, the mountain people still show a strong genetic link to the ancient remains.

“This is not something that you see in most other regions of the world,” said Dr. Reich.

In 2015, Dr. Reich and his colleagues found that some living people in the Amazon carry some DNA that’s most similar to that of people who live today in Australia and New Guinea.

The researchers speculated that their ancestry included an unknown group, which the scientists called Population Y, who separately made their way into the Americas.

In their new study, Dr. Reich and his colleagues found no trace of Population Y — but Dr. Willerslev’s team succeeded in identifying their DNA in some of the 10,400-year-old skeletons in Brazil.

“The million-dollar question obviously is, how did this happen?” Dr. Willerslev said.

Perhaps another group of Asians entered the Americas long before the ancestors of the man from Spirit Cave and other early Native Americans. Maybe they interbred with people in the Amazon before disappearing altogether.

Or perhaps a few of the early members of the southern branch happened to have some odd genes that survived through the generations.

The new rush of genetic samples reflects an improving relationship between scientists and indigenous peoples. For decades, many tribes rejected requests for DNA from researchers.

The man from Spirit Cave, for example, was dug up by archaeologists in 1940 and stored in a museum. The local tribe, the Fallon Paiute-Shoshone, didn’t learn of the body till 1996. For years they fought for its repatriation.

“It’s utterly disrespectful,” said Rochanne L. Downs, a member of the tribe’s cultural committee. “If someone went into Arlington Cemetery and dug the grave of one of soldiers and took their medals, there would be outrage.”

Initially, the tribe was opposed to looking for DNA in the skeleton, because scientists would have to destroy much of it. Dr. Willerslev met with the tribe and explained that he would require only a tooth and a small piece of ear bone.

The tribe agreed to give him one shot at finding DNA in the Spirit Cave remains.

Dr. Willerslev’s results led the Bureau of Land Management to turn over the skeleton to the tribe. They buried the man from Spirit Cave at an undisclosed location last year.

Ms. Downs wouldn’t rule out similar studies in the future, but said each request would require careful consideration.

“It’s all going to be on a case-by-case basis,” she said. “The main thing is our respect for the remains.”

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Researchers walk back major ocean warming result

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Scripps Pier after sunset in La Jolla, California. Image via Hayne Palmour IV/ San Diego Union-Tribune/ os Angeles Times.http://www.latimes.com/science/sciencenow/la-sci-sn-oceans-heat-error-20181114-story.html

This is good news. It is less certain today that Earth’s oceans are 60% warmer than we thought (although they may still be that warm). As reported in the Los Angeles Times today (November 14, 2018), researchers with UC San Diego’s Scripps Institution of Oceanography and Princeton University have had to walk back a widely reported scientific result – based on a paper published in Nature last month – showing that showed Earth’s oceans were heating up dramatically faster than previously thought, as a result of climate change.

The October 31 paper in Nature stated the oceans had warmed 60% more than outlined by the United Nations’ Intergovernmental Panel on Climate Change (IPCC). On November 6, mathematician Nic Lewis posted his criticisms of the paper at Judith Curry’s blog. Both Lewis and Curry are critics of the scientific consensus that global warming is ongoing and human-caused.

In his November 6 blog post, Lewis pointed out flaws in the October 31 paper. The authors of the October 31 paper now say they’ve redone their calculations, and – although they find the ocean is still likely warmer than the estimate used by the IPCC – they agree that they “miffed” the range of probability. They can no longer support the earlier statement of a heat increase 60% greater than indicated. They now say there is a larger range of probability, between 10% and 70%, as other studies have already found.

A correction has been submitted to Nature.

The Los Angeles Times reported that one of the co-author’s on the paper – Ralph Keeling at the Scripps Institution of Oceanography – “took full blame” and thanked Lewis for alerting him to the mistake. Keeling told the Los Angeles Times:

When we were confronted with his insight it became immediately clear there was an issue there. We’re grateful to have it be pointed out quickly so that we could correct it quickly.

In the meantime, the Twitter-verse today has done the expected in a situation like this, where a widely reported and dramatic climate result has had to be walked back. Many are making comments like this one:

But cooler heads on Twitter and elsewhere in the media are also weighing in, pointing out – as has been necessary to point out time and again – that science is not a “body of facts.” Science is a process. Part of the reason scientists publish is so that other scientists can find errors in their work, so that the errors can be corrected.

All scientists know this. The Los Angeles Times explained it this way:

While papers are peer-reviewed before they’re published, new findings must always be reproduced before gaining widespread acceptance throughout the scientific community …

The Times quoted Gerald Meehl, a climate scientist at the National Center for Atmospheric Research in Boulder, Colorado, as saying:

This is how the process works. Every paper that comes out is not bulletproof or infallible. If it doesn’t stand up under scrutiny, you review the findings.

Bottom line: An error has been found in the October 31, 2018 paper published in Nature – showing an increase in ocean warming 60% greater than that estimated by the IPCC. The authors have acknowledged the error, and a correction has been submitted to Nature.

October 31 paper in Nature: Quantification of ocean heat uptake from changes in atmospheric O2 and CO2 composition

November 6 blog post by Nic Lewis: A major problem with the Resplandy et al. ocean heat uptake paper

Deborah Byrd

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Upsettingly Large Fungus in Michigan Weighs 440 Tons and Is 2500 Years Old

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[unable to retrieve full-text content]

  1. Upsettingly Large Fungus in Michigan Weighs 440 Tons and Is 2500 Years Old  Gizmodo
  2. Could this giant 2500-year-old fungus hold the cure to cancer?  Mother Nature Network
  3. Full coverage



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NASA wants Canadian boots on the moon but feds still pondering space options

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OTTAWA — The Trudeau government faced criticism Wednesday for a tepid response to the head of the U.S. space agency saying he wants to see Canadian astronauts walking on the moon in the near future.

Jim Bridenstine, the administrator of he National Aeronautics and Space Administration, said a reconstituted lunar program is the first step toward deeper space exploration, including a mission to Mars.

On a two-day trip to Ottawa, the NASA chief made an impassioned pitch for Canada to continue its decades-long space partnership with the U.S., including by supplying astronauts.

NASA is embarking on the creation of its new Lunar Gateway, a space station it is planning to send into orbit around the moon starting in 2021. The agency wants to create a “sustainable lunar architecture” that would allow people and equipment to go back and forth to the moon regularly, Bridenstine said.

“If Canadians want to be involved in missions to the surface of the moon with astronauts, we welcome that. We want to see that day materialize,” he told a small group of journalists in Ottawa ahead of his keynote speech to the Aerospace Industries Association of Canada.

“We think it would be fantastic for the world to see people on the surface of the moon that are not just wearing the American flag, but wearing the flags of other nations.”

The U.S. is seeking broad international support for its new lunar initiative, Bridenstine told the industry conference. He said NASA wants Canada’s expertise in artificial intelligence and robotics, which could include a next-generation Canadarm on the Lunar Gateway and more Canadian technology inside.

Innovation Minister Navdeep Bains, a vocal booster of Canada’s AI hubs in Ontario and Quebec, said the government is committed to sustaining its partnership with NASA, but he had no specifics.

The minister said the government is still working on a long-awaited space policy that has many dimensions and will be made public before next fall’s federal election.

“At this stage, we would not take anything off the table,” Bains told reporters, when on pressed on the possibility of contributing astronauts to moon missions. “We demonstrated very clearly we want to work with NASA. We want to work with other allies as well.”

The head of one leading Canadian space technology firm said he and many other business leaders at the conference were surprised by the government’s apparent lack of enthusiasm for Bridenstine’s ambitious request.

“There was a lot of excitement about the opportunity that was clearly being given to Canada here,” Mike Greenley, the president of MDA, said in an interview. “I’m a little bit concerned about that lack of response.”

MDA makes sensors, robots and components for satellites.

Greenley said it is possible the government is still considering its options, but given the urgency of the U.S. timetable, that might not be wise.

“The concern would be if we wait too long we can miss the opportunity,” he said. “We best not ponder this too long.”

Greenley said he’d like to see Canadian astronauts on the moon one day, but to get to that stage Canada needs to participate in NASA’s broader lunar program.

Bridenstine said the return to the moon is a stepping stone to a much more ambitious goal: exploration that could include reaching Mars in the next two decades.

“The moon is, in essence, a proving ground for deeper space exploration,” he said.

Marc Garneau, who was the first Canadian to reach outer space in 1984 and is now Canada’s transport minister, told the conference he wants Canada to continue being a “star player” in all fields of the aerospace industry. But he had no new space initiatives to announce.

On Dec. 3, Canadian astronaut David Saint-Jacques will travel to the International Space Station on his first mission.

Mike Blanchfield, The Canadian Press


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