Ancient DNA Sheds New Light on Human Migrations in the Americas - Canadanewsmedia
Connect with us

Science

Ancient DNA Sheds New Light on Human Migrations in the Americas

Published

on


NEW YORK (GenomeWeb) – Three studies published today are offering a new look at the multifaceted population movements and expansions that marked the peopling of the Americas.

For the first of the studies, published online today in Science, researchers from the University of Copenhagen, the University of California, and elsewhere considered ancient genome sequence data for 15 individuals found at sites that stretched from present-day Alaska to Patagonia and that dated as far back as 10,000 years or more.

Through comparisons with genomic data for hundreds of individuals from modern-day populations, the team teased out rapid, but patchy, population spread following initial migrations into North and South America.

“We find that once south of eastern Beringia, Native Americans radiated and gave rise to multiple populations, some of which are visible in the genetic record only as unsampled populations, and who at different times expanded to different portions of the continent, though not as extensively as the initial peopling,” the authors wrote.

Although all of the ancient individuals shared genetic features with Native Americans, the researchers saw more subtle relationships pointing to past population migrations and diversifications. For example, the sample set included a tooth from a toddler on Alaska’s Seward Peninsula, dated at roughly 9,000 years ago, with genetic profiles resembling those in Beringian individuals.

“This one small tooth is a treasure trove of information about Alaska’s early populations, not only their genetic affinities but also their movements, interactions with other people and diet,” co-author Jeffrey Rasic, a researcher with the US National Park Service, said in a statement.

Meanwhile, using “Paleoamerican” samples and a sample from a 19th century individual from the Andaman Islands, the team saw signs of a population with genetic ties to Australasia that was present in South America roughly 11,700 years ago, but has not been detected in North America.

“Overall, our findings suggest that soon after arrival, South Americans diverged along multiple geographic paths,” the authors wrote. “That process was further complicated by the arrival of a second independent migration and gene flow in Middle to Late Holocene times. Later admixture potentially reduced the Australasian signature that might have been carried by earlier inhabitants.”

A related study published online today in Science Advances focused on ancient population adaptations to cold, low oxygen environments with high exposure to ultraviolet light at high-altitude sites in the South American Andes. There, an Emory University- and University of Chicago-led team did whole-genome shotgun sequencing on seven samples dating back 1,400 years to nearly 7,000 years, spanning three distinct archeological periods.

“Contact with Europeans had a devastating impact on South American populations, such as the introduction of disease, war, and social disruption,” first author John Lindo, an anthropology and human genetics researcher affiliated with Emory and the University of Chicago, said in a statement. “By focusing on the period before that, we were able to distinguish environmental adaptations from adaptations that stemmed from historical events.”

Based on their ancient genome data, new sequences for dozens of individuals from present-day populations, and available population genotyping profiles, the researchers estimated that permanent populations have occupied the Andean highlands since roughly 9,000 years ago, remaining more robust after European arrivals that dramatically affected lowland populations in South America.

When it came to high-altitude adaptations in the region, the team found evidence of alterations affecting heart-related genes rather than at hypoxia-associated genes implicated in low oxygen-response elsewhere.

The researchers also saw signs of selection affecting genes such as the intestinal enzyme-coding gene MGAM that appear to contribute to starch digestion, likely reflecting potato-rich diets in the area. And they detected more recent signs of positive selection in the Andes involving genes known to respond to the types of infectious diseases introduced by Europeans.

Finally, in a paper published online today in Cell, researchers from Harvard Medical School, the Max Planck Institute for the Science of Human History, and elsewhere described three main migrations from a related ancestral source population into South America based on genome-wide sequence data for 49 ancient individuals in the Central Andes, southern South America, Brazil, and Belize going back almost 11,000 years.

“This broader dataset reveals a common origin of North, Central, and South Americans as well as two previously unknown genetic exchanges between North and South America,” co-senior author David Reich, a genetics researcher at Harvard, said in a statement.

While the spread of Clovis culture from North America into South America has not been documented, the team’s latest genetic results revealed shared ancestry between Clovis individuals and individuals who lived in what is now Brazil more than 9,000 years ago. Samples from parts of Central and South America that were dated at less than 9,000 years old pointed to a population replacement that ousted individuals with Clovis-related genetic ancestry and was followed by ongoing population continuity.

The researchers also described another previously unappreciated relationship between populations with shared ancestry in the southern Peruvian Andes and California’s Channel Islands. 

Reich noted that that study lacked ancient representatives from several important locations, including Amazonia, northern South America, and the Caribbean. Consequently, he said, “[f]illing in these gaps should be a priority for future work.”

Let’s block ads! (Why?)



Source link

Continue Reading

Science

Scientists acknowledge critical errors in study of how fast the oceans are warming

Published

on

By


In this July 21, 2017 file photo, researchers look out from the Finnish icebreaker MSV Nordica as the sun sets over sea ice floating on the Victoria Strait along the Northwest Passage in the Canadian Arctic Archipelago.

David Goldman / ASSOCIATED PRESS

The findings suffer from too much doubt to definitively support the paper’s conclusion, says a study co-author: ‘Unfortunately, we made mistakes’

Scientists behind a major study that claimed the Earth’s oceans are warming faster than previously thought now say their work contained inadvertent errors that made their conclusions seem more certain than they actually are.

Two weeks after the high-profile study was published in the journal Nature, its authors have submitted corrections to the publication. The Scripps Institution of Oceanography, home to several of the researchers involved, also noted the problems in the scientists’ work and corrected a news release on its website, which previously had asserted that the study detailed how the Earth’s oceans “have absorbed 60 percent more heat than previously thought.”

“Unfortunately, we made mistakes here,” said Ralph Keeling, a climate scientist at Scripps, who was a co-author of the study. “I think the main lesson is that you work as fast as you can to fix mistakes when you find them.”

The central problem, according to Keeling, came in how the researchers dealt with the uncertainty in their measurements. As a result, the findings suffer from too much doubt to definitively support the paper’s conclusion about just how much heat the oceans have absorbed over time.

The central conclusion of the study — that oceans are retaining ever more energy as more heat is being trapped within Earth’s climate system each year — is in line with other studies that have drawn similar conclusions. And it hasn’t changed much despite the errors. But Keeling said the authors’ miscalculations mean there is actually a much larger margin of error in the findings, which means researchers can weigh in with less certainty than they thought.

Where they don't make sense — with this one, it's fairly obvious it didn't make sense — I look into them more deeply

“I accept responsibility for what happened because it’s my role to make sure that those kind of details got conveyed,” Keeling said.

The study’s lead author was Laure Resplandy of Princeton University. Other researchers were with institutions in China, Paris, Germany and the U.S. National Center for Atmospheric Research and Geophysical Fluid Dynamics Laboratory.

“Maintaining the accuracy of the scientific record is of primary importance to us as publishers and we recognize our responsibility to correct errors in papers that we have published,” Nature said in a statement to The Post. “Issues relating to this paper have been brought to Nature’s attention and we are looking into them carefully. We take all concerns related to papers we have published very seriously and will issue an update once further information is available.”

The original study, which appeared on Oct. 31, derived a new method for measuring how much heat is being absorbed by the oceans. Essentially, the authors measured the volume of gases, specifically oxygen and carbon dioxide, that have escaped the ocean in recent decades and headed into the atmosphere as it heats up. They found that the warming “is at the high end of previous estimates” and suggested that as a result, the rate of global warming itself could be more accelerated.

The results, wrote the authors, may suggest there is less time than previously thought to curb greenhouse gas emissions. The study drew considerable media attention, including from The Post.

However, not long after publication, an independent Britain-based researcher named Nicholas Lewis published a lengthy blog post saying he had found a “major problem” with the research.

I think the main lesson is that you work as fast as you can to fix mistakes when you find them

“So far as I can see, their method vastly underestimates the uncertainty,” Lewis said in an interview Tuesday, “as well as biasing up significantly, nearly 30 percent, the central estimate.”

Lewis added that he tends “to read a large number of papers, and, having a mathematics as well as a physics background, I tend to look at them quite carefully, and see if they make sense. And where they don’t make sense — with this one, it’s fairly obvious it didn’t make sense — I look into them more deeply.”

Lewis has argued in past studies and commentaries that climate scientists are predicting too much warming because of their reliance on computer simulations, and that current data from the planet itself suggests global warming will be less severe than feared.

It isn’t clear whether the authors agree with all of Lewis’ criticisms, but Keeling said “we agree there were problems along the lines he identified.”

Paul Durack, a research scientist at the Lawrence Livermore National Laboratory in California, said promptly acknowledging the errors in the study “is the right approach in the interests of transparency.”

But he added in an email, “This study, although there are additional questions that are arising now, confirms the long known result that the oceans have been warming over the observed record, and the rate of warming has been increasing,” he said.

Gavin Schmidt, head of the NASA Goddard Institute for Space Studies, followed the growing debate over the study closely on Twitter and said that measurements about the uptake of heat in the oceans have been bedeviled with data problems for some time — and that debuting new research in this area is hard.

“Obviously you rely on your co-authors and the reviewers to catch most problems, but things still sometimes slip through,” Schmidt wrote in an email.

Schmidt and Keeling agreed that other studies also support a higher level of ocean heat content than the Intergovernmental Panel on Climate Change, or IPCC, saw in a landmark 2013 report.

Overall, Schmidt said, the episode can be seen as a positive one.

“The key is not whether mistakes are made, but how they are dealt with — and the response from Laure and Ralph here is exemplary. No panic, but a careful reexamination of their working — despite a somewhat hostile environment,” he wrote.

“So, plus one for some post-publication review, and plus one to the authors for reexamining the whole calculation in a constructive way. We will all end up wiser.”

Let’s block ads! (Why?)



Source link

Continue Reading

Science

NASA to invite designs for AI lunar robot

Published

on

By


By: PTI | New Delhi |

Published: November 14, 2018 5:45:44 pm

A space robotics challenge in the past aimed to programme NASA’s humanoid Valkyrie to perform human-like tasks.

NASA is planning to launch a challenge for the public and scientific community to design a self-assembling robot with artificial intelligence that can explore the surface of the Moon, William Harris, CEO of Space Centre Houston said. Space Centre Houston in the US, the official visitor centre for NASA Johnson Space Centre, conducts regular public outreach programmes to engage people of various ages and diverse backgrounds in scientific research.

These programmes encourage students and scientists to ideate innovative solutions for problems that the US space agency is trying to overcome in order to carry out successful space exploration missions. “The next challenge is for the Moon — it will be announced next year — to develop a self assembling robot or rover on the Moon’s surface that has an artificial intelligence platform so it can make decisions based on what it is learning about the lunar surface,” Harris told PTI in an interview.

[embedded content]

“The reality is, when we sent humans to the Moon back in the 1960s, just going there and coming back safely was a huge accomplishment. We did not do a huge amount of science during those missions,” he said. Most of the astronauts then were test pilots. The first and only scientist to have visited the Moon is Harrison Schmitt, an American geologist, who is now the last living crew member of Apollo 17, Harris said. There was very little scope to perform scientific experiments, and to date there is a lot we do not know about the Moon, he said. However, the astronauts that NASA recruits now are scientists.

With plans underway to take humans back to the lunar surface, the US space agency is working on efficient technologies that can assist astronauts to conduct scientific experiments on the Moon. In the recent decades, evidence of frozen water beneath the surface of the Moon has emerged. This not only presents the possibility for the Moon to host some form of primitive life, but also opens avenues for future astronauts to harvest water and set up a space colony. The water could also be broken down to provide hydrogen fuel, using which we could send missions into deeper space, Harris said.

Also read: Samsung Galaxy Tab S4 review: The best Android tablet. Period.

“NASA has come to recognise that you can become to insular with your own team. So it is better to open up to the general public to see if somebody has ideas that can help us address different challenges,” he said. Harris gave an example of a space robotics challenge in the past, that aimed to programme NASA’s humanoid Valkyrie to perform human-like tasks.

“Within the group of ten semi-finalists, we had teams from two of the top universities. But the winner of the challenge was a stay-at-home dad, who came with his 6-year-old son,” said Harris. His solutions are now being used by NASA to programme Valkyrie. Involving the public in this way can help space programmes flourish and break new grounds, he said.

Harris was in New Delhi as a part of a delegation of representatives seeking to strengthen ties with Indian companies and to learn about the latest developments in the country’s business environment and industries like aerospace, healthcare and information technology.

For all the latest Technology News, download Indian Express App

Let’s block ads! (Why?)



Source link

Continue Reading

Science

Scientists acknowledge key errors in study of how fast the oceans are warming

Published

on

By


Scientists behind a major study that claimed the Earth’s oceans are warming faster than previously thought now say their work contained inadvertent errors that made their conclusions seem more certain than they actually are.

Two weeks after the high-profile study was published in the journal Nature, its authors have submitted corrections to the publication. The Scripps Institution of Oceanography, home to several of the researchers involved, also noted the problems in the scientists’ work and corrected a news release on its website, which previously had asserted that the study detailed how the Earth’s oceans “have absorbed 60 percent more heat than previously thought.”

“Unfortunately, we made mistakes here,” said Ralph Keeling, a climate scientist at Scripps, who was a co-author of the study. “I think the main lesson is that you work as fast as you can to fix mistakes when you find them.”

The central problem, according to Keeling, came in how the researchers dealt with the uncertainty in their measurements. As a result, the findings suffer from too much doubt to definitively support the paper’s conclusion about just how much heat the oceans have absorbed over time.

The central conclusion of the study — that oceans are retaining ever more energy as more heat is being trapped within Earth’s climate system each year — is in line with other studies that have drawn similar conclusions. And it hasn’t changed much despite the errors. But Keeling said the authors’ miscalculations mean there is actually a much larger margin of error in the findings, which means researchers can weigh in with less certainty than they thought.

Where they don't make sense — with this one, it's fairly obvious it didn't make sense — I look into them more deeply

“I accept responsibility for what happened because it’s my role to make sure that those kind of details got conveyed,” Keeling said.

The study’s lead author was Laure Resplandy of Princeton University. Other researchers were with institutions in China, Paris, Germany and the U.S. National Center for Atmospheric Research and Geophysical Fluid Dynamics Laboratory.

“Maintaining the accuracy of the scientific record is of primary importance to us as publishers and we recognize our responsibility to correct errors in papers that we have published,” Nature said in a statement to The Post. “Issues relating to this paper have been brought to Nature’s attention and we are looking into them carefully. We take all concerns related to papers we have published very seriously and will issue an update once further information is available.”

The original study, which appeared on Oct. 31, derived a new method for measuring how much heat is being absorbed by the oceans. Essentially, the authors measured the volume of gases, specifically oxygen and carbon dioxide, that have escaped the ocean in recent decades and headed into the atmosphere as it heats up. They found that the warming “is at the high end of previous estimates” and suggested that as a result, the rate of global warming itself could be more accelerated.

The results, wrote the authors, may suggest there is less time than previously thought to curb greenhouse gas emissions. The study drew considerable media attention, including from The Post.

However, not long after publication, an independent Britain-based researcher named Nicholas Lewis published a lengthy blog post saying he had found a “major problem” with the research.

I think the main lesson is that you work as fast as you can to fix mistakes when you find them

“So far as I can see, their method vastly underestimates the uncertainty,” Lewis said in an interview Tuesday, “as well as biasing up significantly, nearly 30 percent, the central estimate.”

Lewis added that he tends “to read a large number of papers, and, having a mathematics as well as a physics background, I tend to look at them quite carefully, and see if they make sense. And where they don’t make sense — with this one, it’s fairly obvious it didn’t make sense — I look into them more deeply.”

Lewis has argued in past studies and commentaries that climate scientists are predicting too much warming because of their reliance on computer simulations, and that current data from the planet itself suggests global warming will be less severe than feared.

It isn’t clear whether the authors agree with all of Lewis’ criticisms, but Keeling said “we agree there were problems along the lines he identified.”

Paul Durack, a research scientist at the Lawrence Livermore National Laboratory in California, said promptly acknowledging the errors in the study “is the right approach in the interests of transparency.”

But he added in an email, “This study, although there are additional questions that are arising now, confirms the long known result that the oceans have been warming over the observed record, and the rate of warming has been increasing,” he said.

Gavin Schmidt, head of the NASA Goddard Institute for Space Studies, followed the growing debate over the study closely on Twitter and said that measurements about the uptake of heat in the oceans have been bedeviled with data problems for some time — and that debuting new research in this area is hard.

“Obviously you rely on your co-authors and the reviewers to catch most problems, but things still sometimes slip through,” Schmidt wrote in an email.

Schmidt and Keeling agreed that other studies also support a higher level of ocean heat content than the Intergovernmental Panel on Climate Change, or IPCC, saw in a landmark 2013 report.

Overall, Schmidt said, the episode can be seen as a positive one.

“The key is not whether mistakes are made, but how they are dealt with — and the response from Laure and Ralph here is exemplary. No panic, but a careful reexamination of their working — despite a somewhat hostile environment,” he wrote.

“So, plus one for some post-publication review, and plus one to the authors for reexamining the whole calculation in a constructive way. We will all end up wiser.”

The part of me that lurks underneath isn’t finished grappling with this French journalist acting the tough, hard-bitten reporter
The tests claim to be able to identify food sensitivities associated with headaches, lethargy, brain fog, depression and an huge array of other symptoms
We concluded that practically all of western Canada, and the sizeable conservative minority in eastern Canada, were practically unrepresented in the national media
What should not change are the ideas and perspectives that animate the National Post. Its founding insight is as correct today as it was two decades ago

Let’s block ads! (Why?)



Source link

Continue Reading

Trending

Copyright © 2018 Canada News Media

%d bloggers like this: