Man's Ancient Past: Anzick Child's Ancient Genome Link between Asians and Native Americans

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Ancestry of first Americans revealed by a boy's genome

http://www.newscientist.com/article/mg22129562.100-ancestry-of-first-americans-revealed-by-a-boys-genome.html?full=true#.Uv0CnCmYa9I

by Catherine Brahic

February 13, 2014

The genes of a boy who died 12,600 years ago show that all indigenous people

in the Americas seem to be descended from the same group of ancestors

WE MAY never know who the Anzick child was. Why he died, just 3 years old, in the foothills of the American Rockies; why he was buried, 12,600 years ago, beneath a huge cache of sharpened flints; or why his kin left him with a bone tool that had been passed down the generations for 150 years.

One thing, however, is certain: his afterlife is anything but ordinary. This week, geneticists announced that the boy is the earliest ancient American to have his entire genome sequenced. Incredibly, he turns out to be a direct ancestor of most tribes in Central and South America – and probably the US too – as well as a very close cousin of Canadian tribes.

"It's crazy," says Eske Willerslev of the University of Copenhagen in Denmark, who led the genomic analysis. "Finding someone who is directly ancestral to the entire population of a continent – that just does not happen. I don't think it would ever happen in Europe, or in Siberia. There are very few places where this could happen."

"The reason," he says, "must be that this skeleton is really close to the source – really close to the 'Adam' [of the Americas]. I think that is the only explanation."

The find offers the first genetic evidence for what Native Americans have claimed all along: that they are directly descended from the first Americans. It also confirms that those first Americans can be traced back at least 24,000 years, to a group of early Asians and a group of Europeans who mated near Lake Baikal in what is now Siberia. And it dispels a controversial theory that the Americas were first populated by west Europeans who somehow crossed the Atlantic Ocean.

The boy was discovered in Montana in 1968, when diggers working on land owned by the Anzick family accidentally ploughed into a huge cache of stone tools. The flints were typical of the Clovis period, a short archaeological period in North America lasting from 13,000 to 12,500 years ago. Beneath them lay a handful of bone artefacts and a skeleton.

Clovis artefacts are scattered all over the western US. Archaeologists largely believe that the first Americans arrived by a land bridge from Asia about 15,000 years ago, and some went on to develop Clovis tools (see "A history of the first Americans in 9½ sites").

Willerslev and his colleagues were able to extract enough viable DNA from the boy's badly preserved bones to sequence his entire genome.

They then compared this with DNA samples from 143 modern non-African populations, including 52 South American, central American and Canadian tribes.

The comparison revealed a map of ancestry. The Anzick child is most closely related to modern tribes in Central and South America, and is equally close to all of them – suggesting his family were common ancestors. To the north, Canadian tribes were very close cousins. DNA comparisons with Siberians, Asians and Europeans show that the further west populations are from Alaska, the less related they are to the boy.

Fully sequenced genomes remain rare, so the bulk of the analysis was done by looking at genetic markers known as single nucleotide polymorphisms or SNPs. To confirm the pattern, Willerslev and his team sequenced full genomes from three contemporary Mayan and Karitiana individuals in Central and South America.

The findings offer genetic confirmation that the first Americans crossed the land bridge that once stretched from Siberia to Alaska across the Bering Strait.

"The Clovis population seems to be more closely related to South Americans than to native North Americans," says David Reich of Harvard Medical School in Boston. "That's telling you that the Clovis sample seems to have occurred after the initial split of the lineages that gave rise to native South Americans and native North Americans."

Unfortunately, long-standing tensions between US tribes and scientists mean there is no significant genetic data available from these peoples (see Leader, "An ancient genome alone can't heal long-standing rifts"). Having that data, says Reich, could help determine which groups lie on either side of the North and South American family tree.

In November, Willerslev published the genome of another ancient boy, the 24,000-year-old Mal'ta boy, from the shores of Russia's Lake Baikal. The boy's DNA showed he descended from a mating between early Asians and proto-Europeans, and that he is related to modern South Americans. Like modern South American DNA, the Anzick DNA is a mix of Mal'ta and other Asian DNA, pointing to a "source" population for the first Americans, probably in far eastern Siberia (see map).

But how many first Americans were there, and did they come all at once or as a slow trickle? "The most likely scenario is that a single migration of people into the heartland of North America around 15,000 years ago gave rise to the Clovis and their descendants, which includes modern Native Americans," says Mike Waters of Texas A&M University in College Station, a co-author with Willerslev on the latest study. "This is supported by the archaeological and genetic evidence."

In fact, Willerslev wagers that the first group to cross over from Siberia was no more than 100 strong. Another of Willerslev's co-authors, David Meltzer of the Southern Methodist University in Dallas, Texas, is more cautious. For now, he says, we have just one genetic data point. And the study cannot address whether early migrants came through the interior of North America, or hugged the coast. The interior route would not have opened until 13,500 years ago, but earlier remains have been found in Monte Verde in Chile. So a first group may have come down the coast, and later groups from the same source population followed inland, carrying the same genetic heritage.

Perhaps the most evocative mystery that remains is the identity of the boy himself. His is the only known Clovis grave. The tools he was buried with – including one that was already 150 years old and fashioned from an elk bone – would have been priceless heirlooms to those who carried them. Yet they left them in the ground with a child.

We may never know who the Anzick child was, but scientists and local US tribes have agreed to lay him back to rest (see "Tribal healing: Anzick child genome changed my life"). He will be reburied sometime in the next few months.

Journal reference: Nature, DOI: 10.1038/nature13025

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National Geographic - link here

"Oldest Burial Yields DNA Evidence of First Americans

Ancient genome confirms link between Asians and Native Americans."

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Prehistoric Connections from Montana State University on Vimeo.

MSU News Service
Tel: (406) 994-4571
msunews@montana.edu

Shane Doyle links Montana tribes, 

international researchers over prehistoric boy

http://www.montana.edu/news/12421/shane-doyle-links-montana-tribes-international-researchers-over-prehistoric-boy

by Evelyn Boswell, MSU News Service

February 12, 2014

BOZEMAN – On a beautiful fall day, Shane Doyle sang a somber song for a young boy who was buried some 12,600 years ago south of present-day Wilsall.

“I wanted to honor the spirit of the boy. There was a disturbance there. I felt like there needed to be some healing,” said the enrolled member of the Crow tribe and an instructor in the Native American Studies program at Montana State University.

Sarah Anzick said the honor song Doyle sang last September was beautiful, touching and a fitting tribute for the child she has known about since she was two years old, approximately the same age the boy was when he died from unknown causes.  Anzick’s parents own the property where his skull and bone fragments were discovered in 1968. His are among the oldest human remains found in North America and the only Late Pleistocene human from a Clovis burial site.

Doyle’s song also helped confirm that he was the right person to serve as liaison between Montana tribes and an international team of scientists who conducted a genetic study that led to major findings that will be published in the Feb. 13 issue of the journal, Nature, said Anzick, a co-author and molecular biologist on the project.

“We were so fortunate that he was willing to join our team and facilitate the connections with the Native American communities,” Anzick said. “This is something I had tried to do many years ago, but was unsuccessful. “

A press release from Nature said the team of scientists reported the first complete genome sequence of an ancient North American human – the boy whose skeletal fragments were discovered near Wilsall, in association with dozens of ochre-covered stone tools.   The scientists found that the boy belonged to a population from which many contemporary Native Americans descended – including Doyle -- and is closely related to all indigenous American populations.

Evidence of the Past: A Map and Status of Ancient Remains.
For burial specifics - go to link here

The study showed very early division within Native Americans, but all groups from which scientists have DNA show a close relationship to the Anzick child. The scientists said their study also presents one of the strongest challenges so far to the hypothesis about the origin of the Clovis culture.   It was generally believed that the Clovis people originally came from Asia and were directly related to contemporary Native Americans, but an alternative theory had suggested that Clovis predecessors emigrated from southwestern Europe. Clovis, with its distinctive stone tools, is the oldest widespread archaeological complex in North America. It dates to around 12,600-13,000 years ago.

Doyle, who is one of 42 co-authors of the Nature paper, said he isn’t a geneticist, but he has experience bringing MSU and the Montana tribes together. He, for one, is the link between MSU nursing students and tribal clinics. Doyle grew up on the Crow Indian Reservation and earned his bachelor’s, master’s and doctoral degrees at MSU.  For his doctorate in education, he studied the Absaroka Agency archaeological excavation, specifically how tribes and archaeologists can best collaborate. He currently teaches Native American belief and philosophy at MSU. He has been a member of the Bobcat Singers drum group since 1989.

He first met Eske Willerslev, principal investigator for the Anzick project, in September when Willerslev came to Montana, Doyle said. Willerslev is a world-renowned ancient DNA researcher at the Center for GeoGenetics at the University of Copenhagen in Denmark. Willerslev became involved in the Montana study through Anzick and archaeologist Mike Waters, director of the Center for the Study of the First Americans at Texas A & M University. Waters’ predecessor conducted research on Kennewick Man, a prehistoric man found on the banks of the Columbia River in 1996.

Besides singing a Northern Cheyenne honor song at the boy’s burial site, Doyle drove Willerslev to the Crow, Northern Cheyenne, Blackfeet and Flathead Indian Reservations to meet with the tribal historic preservation officers and other Native Americans to explain the genetic study and consult with the tribes about the boy’s reburial. Doyle said he would have taken Willerslev to more reservations, but they didn’t have enough time.

Willerslev said he understands the many feelings that are involved when scientists study ancient human remains. He understands why members of the tribes hold strong feelings about the past.

From his Montana trip, he said, “I learned that all the cultural representatives I met in the tribes of Montana are clever peoples with a deep cultural and historical insight, and I was very well received by them all. A great experience. Shane guided me through this process. Without him, I would have been lost.”

In December, Doyle flew to Denmark where he spoke to Willerslev’s graduate students and met Waters for the first time.

Earlier this week, as the Nature publication neared, Doyle, Willerslev, Waters and Anzick spoke at two Montana press conferences about their genetic findings, plans for a respectful reburial, the project’s history, and implications for archaeology in the future. The first press conference was held Feb. 11 at Little Big Horn College in Crow Agency. The second was held Feb. 12 at the Montana Historical Society in Helena, where all the artifacts from the Anzick site will be displayed.

“This is truly a state treasure to be shared and enjoyed by all,” Anzick said.

Doyle said it’s obvious from the large number of artifacts that were found with the boy that he was loved.

Livingston archaeologist Larry Lahren, an MSU graduate who has studied the Anzick site for 40 years, said in a recent lecture at MSU’s Museum of the Rockies, that “You would be overwhelmed to look at the collection to see the size and quantity of the materials.”

He added that the site south of Wilsall wasn’t a cache, but definitely an ancient burial site. In addition to the skull and bone fragments that yielded significant genetic information were the remains of another boy. That boy was six to eight years old when he died. He was buried about 9,000 years ago.

Doyle, the father of five children from ages 1 through 9, said he feels for the anguished parents who lost their sons so long ago. He added that normal parental feelings and Native American traditions indicate that it’s time to rebury the boy whose genome is discussed in Nature.

The reburial will occur as soon as this spring and will be as close as possible to the original burial site, Doyle said. One of the major players will likely be Larson Medicinehorse of Crow Agency, who was involved in the reburial of Chief Pretty Eagle almost 20 years ago.

“You feel like it’s morally the right thing to do. It’s the reason why I agreed to help,” Doyle said of the upcoming reburial.

Willerslev, Waters and Anzick agreed.

“As a scientist, I have mixed feelings as the remains may well still hold information to be gained,” Willerslev said. “However, I do respect this wish from the tribes, and I know they feel deeply about why it has to take place. Had it been my child, I would have wished it to be reburied too. As scientists, we have a lot to learn from the tribes.”

Anzick said, “I feel a moral obligation for the reburial and yes, as technology advances, we can always learn more. Had these remains been reburied just 10 years ago, they wouldn’t have revealed what we know today, and I’m certain we can learn even more.

“However, out of respect for the Native American communities and the parents of this child, a reburial is an important part of the equation,” Anzick said. “It is my hope through open communications, dialogue and Native American involvement, we can collaborate toward a working model which leads ultimately to a respectful reburial.”

Waters said, “This was a prehistoric tragedy. Someone lost their child. They lovingly buried this child with artifacts and red ochre. Like Shane pointed out, they would have been valuable and important things to people who were hunters and gathers. They clearly showed the emotions of these early people.

“I appreciate the way Shane has been doing an outstanding job of shepherding us through the process of talking to various Native American groups and finding the path to the proper reburial of these remains,” Waters said.

Doyle said he is impressed with all the scientists on the project.

“They didn’t have to bring me in,” he said.

He added that his life hasn’t been the same since he joined their team. Not only has it led to new interactions and opportunities for future collaborations, but the genetic findings proved what he has always believed.

“It’s one thing to believe and sense that your people have been here for thousands and thousands of years,” Doyle explained. “It’s another thing to have scientific evidence and proof that those paleo-Indians were us and we are them.”

The genetic study led to a rush of profound emotions, Doyle said. It made him proud of his ancestors and the way they cared for the land. It gave him new appreciation for family. He was shocked when he realized that the land where the boy was buried is part of the area included in an 1851 treaty signed by his great-great-great-great-grandfather Mountain Tail.

“All my family comes from this place and so did this little boy,” Doyle said. “We are not only connected by geography, but by blood. It was so moving for me.”  

Evelyn Boswell, (406) 994-5135 or evelynb@montana.edu

Audio Recording at link here

Exploring Evolution Series: Self-Assembling Molecules Like These May Have Sparked Life on Earth

When his students successfully converted chemical precursors into an RNA-like molecule in the

form of a yellow gel, Nicholas Hud scribbled down the surprising recipe. Image: Nicholas Hud

Self-Assembling Molecules Like These

May Have Sparked Life on Earth

http://www.wired.com/wiredscience/2014/02/rna/

by Emily Singer, Quanta Magazine

February 20, 2014

For Nicholas Hud, a chemist at the Georgia Institute of Technology, the turning point came in July of 2012 when two of his students rushed into his office with a tiny tube of gel. The contents, which looked like a blob of lemon Jell-O, represented the fruits of a 20-year effort to construct something that looked like life from the cacophony of chemicals that were available on the early Earth.

To some biochemists, Hud’s attempts to find an evolutionary precursor to ribonucleic acid may have seemed a fool’s errand. The dominant theory to explain the origins of life — known as the RNA world hypothesis — regards ribonucleic acid as the first biological molecule. Its allure comes from the molecule’s dual nature. Unlike DNA, the molecule that provides the blueprint for all living things, RNA acts as both an information carrier and an enzyme, catalyzing reactions. That means the molecule has the potential to copy itself and to pass along its genetic code, two essential components for Darwinian evolution.

If RNA was indeed the first biological molecule, discovering how it first formed would illuminate the birth of life. The basic building blocks of RNA were available on prebiotic Earth, but chemists, including Hud, have spent years trying to assemble them into an RNA molecule with little success. About 15 years ago, Hud grew frustrated with that search and decided to explore an alternative idea: Perhaps the first biological molecule was not RNA, but a precursor that possessed similar characteristics and could more easily assemble itself from prebiotic ingredients. Perhaps RNA evolved from this more ancient molecule, just as DNA evolved from RNA.

Hud’s team started exploring this idea explicitly a decade ago. When the gel formed in 2012, after the testing of dozens of chemicals, Hud’s team knew it had made a significant advance in the chemistry of a possible proto-RNA world. After years of failed attempts, a surprisingly simple chemical recipe had produced a conglomerate of long, ribbonlike molecules whose structure and chemical components resembled those of RNA.

Hud immediately asked the students to recite the protocol they had used for the reaction, scribbling it down as they spoke. “I wanted to be sure that we would always remember how they had obtained [the end-product] by such a simple procedure,” he said. In December 2013, the results were published in the Journal of the American Chemical Society.

The chemist Nicholas Hud proposes that RNA evolved from a molecule
that  was easier to assemble on the early Earth, as illustrated in this model.Photo: Georgia Institute of Technology

“In my opinion, nothing like this has been seen before,” said Stephen Freeland, a biologist at the University of Maryland Baltimore County, who was not involved in the study. Although he isn’t certain that the chemicals Hud picked will end up being the precise components of proto-RNA, Freeland said Hud has “made conceptual progress.”

Hud isn’t the first scientist to explore an alternative chemistry for RNA. But the robustness of his reaction is unique — the molecules seem to seek one another out, reacting without a lot of chemical coaxing. Hud and others say this ease of creation is essential for reactions to have taken place in the chaotic chemical cauldron of early Earth. “Before this, people just didn’t focus on the real-world situation,” Freeland said. “We need something so robust that no matter what the situation is, it will still happen.”

Hud’s team is now testing whether its reactions will work in a messy mix of molecules more analogous to the primordial soup.

Hud’s chemistry — and the concept of proto-RNA in general — still faces hurdles. His molecule possesses a polymer-like structure of repeating units similar to nucleic acids. In RNA and DNA, the sequence of those units is essential for carrying information, allowing those molecules to store and transmit the code of life. But Hud’s molecule uses only two chemical letters, compared with RNA’s four, and the repeating units can easily come apart. That means it doesn’t have the informational content of RNA, an essential characteristic of life.

Proponents of the traditional RNA world hypothesis say that moving from an RNA precursor like Hud’s to RNA itself still represents an incredible challenge, possibly as daunting as making RNA from scratch. If these molecules were successful enough to launch the origins of life, where are they now?

“To me, the proto-RNA idea raises more questions than it answers,” said John Sutherland, a chemist at the MRC Laboratory of Molecular Biology in Cambridge, England, who nonetheless described Hud’s work as elegant and well done. “If it’s too difficult for RNA to assemble chemically, how can a primitive biology invent RNA?”

From Soup to Structure

In the modern cell, cooking up an RNA molecule is a complex process involving multiple enzymes that link a sugar (ribose) to one of four nucleobases — chemical letters that make up the genetic code and come in the flavors guanine, adenine, uracil and cytosine — and a phosphate, which provides the backbone of the structure. Another enzyme ties together repeating units of each of these three components into the long chain of RNA.

But in the pre-biotic Earth, there were no enzymes. So how could the first RNA molecules have formed? According to the RNA world hypothesis, RNA spontaneously came together through geochemical processes. Scientists studying the origins of life have spent the past 40 years trying to figure out exactly how this could have happened, analyzing the likely chemical components of early Earth and devising chemical reactions to bring them together. “The chemistry of making RNA is so difficult that it’s hard to imagine that you could have a one-pot reaction, where molecules come together and spontaneously make this complex molecule,” Hud said.

Scientists have been able to produce a few of these components without enzymes. In 2009, Sutherland and collaborators showed for the first time that they could synthesize one of the basic units of RNA from scratch. They argue RNA could have formed this way in nature, but Hud and Freeland say the precise chemical conditions and steps required for the reaction would have been unlikely to occur in the chaotic chemical cauldron of prebiotic Earth.

* * * * *

My Grandfather’s Ax

Scientists have long considered alternative chemistries for RNA, synthesizing molecules with alien components that have even found their way into biotechnology applications. Nicholas Hud, a chemist at the Georgia Institute of Technology, takes a broader approach — perhaps every component was different and each changed over time. To explain, Hud employs an ancient Greek paradox called “my grandfather’s ax”: If your father replaced the handle and you replaced the blade, the result would be an entirely new ax. “Everyone accepts that DNA comes from RNA and DNA is harder to make than RNA,” Hud said. “So if you’re willing to accept that DNA evolved from RNA, then why not that RNA is product of evolution of proto-RNA?”

* * * * *

An alternative hypothesis is that RNA as we know it has undergone substantial chemical and biological evolution. “The origins of life and the origin of the genetic code are no longer synonymous,” said Antonio Lazcano, a biologist at the National Autonomous University of Mexico in Mexico City and former president of the International Society for the Study of the Origin of Life who was not involved in Hud’s study. “You can have a significant part of the genetic code that will be the outcome of biological evolution and a largely undescribed stage of chemical evolution.”

Scientists have been examining molecules with alternative bases or sugars almost since RNA was proposed as the first biological molecule in the 1960s. But this approach creates an overwhelming set of possible permutations, as each of the three components — sugar, phosphate and base — has numerous potential replacements. “The chemical space becomes enormous,” Hud said. “It’s a really big task to find out what came first.”

Hud’s team started with the bases, looking for candidates that could form something like the traditional base pairs of RNA and DNA, in which certain bases seek each other out like lost lovers; in RNA, adenine binds only with uracil and guanine with cytosine. It’s this pairing that enables the molecules’ unique capacity to store information. Each molecule acts as a template for the next generation, creating a sort of mirror image of its predecessor.

But Hud also wanted base pairs that, unlike traditional bases, could spontaneously assemble into long polymers. “If you have a complex mixture of thousands of molecules, the chemistry relies on what reacts the fastest,” Hud said. “The molecules need to organize themselves.”

Rather than limit themselves to the four bases used in RNA, the members of Hud’s team considered a library of roughly 100 structurally similar molecules, including only those that were predicted to have existed on prebiotic Earth or in meteorites, which may have carried with them essential components of life. “We’re foolish if we don’t think about this: either why nature picked these four or what nature did before picking these four,” Freeland said.

Molecular Recipes

To try to find bases that bond like those of RNA, Hud’s team started mixing chemicals under various conditions. After several years, the researchers homed in on a few promising candidates, most notably two molecules, triaminopyrimidine (TAP) and cyanuric acid (CA). Last year, in a paper published in the Journal of the American Chemical Society, the researchers showed that a slightly modified version of triaminopyrimidine and cyanuric acid self-assemble in water, creating something that resembles traditional base pairs. However, rather than the conventional duo of base pairs, adenine and uracil or cytosine and guanine, the molecules form hexamers, or six-membered rings. The hexamers stack on top of one another, forming long, polymerlike structures. They had found a chemical pairing that spontaneously assembled into a complex, RNA-like arrangement. “We were surprised it worked so well,” Hud said.

Hud’s team set out to tackle the next problem in RNA assembly: How do bases attach to the ribose sugar? In their newest paper, published in the same journal, the researchers showed that TAP and ribose easily bond when mixed in water, creating molecules known as nucleosides. (The finding was especially encouraging because this bond has been difficult to form between sugars and traditional RNA bases.) When the researchers added the other base, CA, and heated the mixture, it formed into long polymers, about the length of genes. It’s these polymers that create the gel that excited Hud’s team.

“I think it’s an important step because it shows that the physical forces that hold genomes together today can be reproduced in the protoworld,” said Frank Schmidt, a biochemist at the University of Missouri in Columbia who was not involved in the studies. “He has shown that you can start with star stuff [chemicals originally produced by stars] and get something with some of the fundamental properties of RNA.”

The beauty of Hud’s chemistry is that the assembly doesn’t require an enzyme or a template — the molecules come together on their own.

According to the protoRNA theory, each of the components of RNA — sugar, base and
phosphate backbone — may have originally taken different forms. Image: Nicholas Hud

Big Questions

However, there are still important differences between Hud’s polymer and RNA. “These lovely properties come at the price of taking a step away from the chemistry we all know,” said Michael Yarus, a molecular biologist at the University of Colorado in Boulder who was not involved in the studies. For example, unlike RNA, each molecule in the stack is linked by a relatively weak kind of bond known as a non-covalent bond. Like a set of magnetic beads that can break apart and reconnect, the structure can separate more easily than RNA, which is more similar to beads knotted on a string. That flexible structure impairs the polymer’s potential to reliably store information in the sequence of bases, which makes up the code of life.

Other big questions include why and how these molecules could have evolved into modern RNAs, considering that it might have been easier for the precursor molecule to maintain the status quo. Proponents of the traditional RNA world view this as a giant obstacle, but Hud disagrees. CA can be converted into uracil and TAP into guanine and adenine with only a few chemical changes, he said. His team is now exploring other candidate bases capable of forming pairs and self-assembling with ribose sugars. The researchers are also looking at alternatives for the other components of RNA, the sugars and phospates, as well as how to stitch together nucleosides in a way that mimics the knotted string of RNA. Even though the final result may look quite different than RNA, Hud argues that because RNA is the superior system, natural selection will favor its creation and drive its precursor to extinction.

Even those who are not convinced of the proto-RNA world say it’s worth exploring the possibilities. “It’s important to have a lot of routes to find the one that really happened, the one that’s highly probable,” Yarus said, adding that how far Hud’s chemistry will travel along that path of probability is not yet clear.

Others are looking at an even broader set of chemical alternatives. In a paper published in November 2013, Freeland and collaborator Jim Cleaves, a chemist at the Earth-Life Science Institute in Tokyo, used computational methods to examine alternative amino acids, which are the building blocks of proteins. The team plans to do the same for the building blocks of RNA. “Hud’s list is just the tip of the iceberg,” Freeland said. “There could be tens of thousands of structures to seriously consider.”

Original story reprinted with permission from Quanta Magazine, an editorially independent division of SimonsFoundation.org whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.

Index to past discussions -

Index to past articles on "Science & Religion"

Stephen Hawking's Newest Proposal: Black Holes have no Event Horizon. Only an Apparent Horizon

An artist conception of a black hole spewing radiation all around it. Image: NASA

A Brief History of Mind-Bending Ideas About Black Holes
http://www.wired.com/wiredscience/2014/01/brief-history-of-black-holes/

by Adam Mann
January 29, 2014

Physicist Stephen Hawking made headlines recently by saying that black holes – the incredibly massive astronomical objects that made him famous – do not exist. Or they exist, but not how we think. Or something. The truth is complicated.

In fact, to really understand where Hawking and the rest of the astrophysics community are coming from, it’s important to know a little history. Just how we arrived at this complex situation is strange, involving a spate of discoveries about the properties of black holes, each solving some previous problem. But, like a hydra sprouting new heads for each one cut off, the solutions generated new difficulties, eventually leading to Hawking’s recent declaration.

The story starts in 1784, when a geologist named John Michell was thinking deeply about Isaac Newton’s theory of gravity. In Newtonian physics, a cannonball can be shot into orbit around the Earth if it surpasses a particular speed, known as the planet’s escape velocity. This speed depends on the mass and radius of the object you are trying to escape from. Michell’s insight was to imagine a body whose escape velocity was so great that it exceeded the speed of light – 300,000 kilometers per second – first measured in 1676 by the Danish astronomer Ole Romer.

Michell presented his results to other scientists, who speculated that massive “dark stars” might exist in abundance in the sky but be invisible because light can’t escape their surfaces. The French mathematician Pierre-Simon Laplace later made an independent discovery of these “dark stars” and both luminaries correctly calculated the very small radius – 6 kilometers – such an object would have if it were as massive as our sun.

After the revolutions of 20th century physics, black holes got much weirder. In 1916, a short while after Einstein published the complex equations underpinning General Relativity (which Einstein himself couldn’t entirely solve), a German astronomer named Karl Schwarzschild showed that a massive object squeezed to a single point would warp space around it so much that even light couldn’t escape. Though the cartoon version of black holes has them sucking everything up like a vacuum cleaner, light would only be unable to escape Schwarzschild’s object if it was inside a particular radius, called the Schwarzschild radius. Beyond this “event horizon,” you could safely leave the vicinity of a black hole.

Trailing above galaxy NGC 4194 is a tidal tail formed by a collision with another galaxy. The bright blue X-ray source found on the left side of the tail is a black hole. Image: X-ray: NASA/CXC/Univ of Iowa/P.Kaaret et al.; Optical: NASA/ESA/STScI/Univ of Iowa/P.Kaaret et al.

Neither Schwarzschild nor Einstein believed this object was anything other than a mathematical curiosity. It took a much better understanding of the lives of stars before black holes were taken seriously. You see, a star only works because it preserves a delicate balance between gravity, which is constantly trying to pull its mass inward, and the nuclear furnace in its belly, which exerts pressure outward. At some point a star runs out of fuel and the fusion at its core turns off. Gravity is given the upper hand, causing the star to collapse. For stars like our sun, this collapse is halted when the electrons in the star’s atoms get so close that they generate a quantum mechanical force called electron degeneracy pressure. An object held up by this pressure is called a white dwarf.

In 1930, the Indian physicist Subrahmanyan Chandrasekhar showed that, given enough mass, a star’s gravity could overcome this electron degeneracy pressure, squeezing all its protons and electrons into neutrons. Though a neutron degeneracy pressure could then hold the weight up, forming a neutron star, the physicist Robert Oppenheimer found that an even more massive object could overcome this final outward pressure, allowing gravity to win and crushing everything down to a single point. Scientists slowly accepted that these things were real objects, not just weird mathematical solutions to the equations of General Relativity. In 1967, physicist John Wheeler used the term “black hole” to describe them in a public lecture, a name that has stuck ever since.

But as researchers studied black holes, they kept finding new ways in which they were bizarre. In 1974, Stephen Hawking made his most famous discovery: black holes can emit radiation. Down at the subatomic scale, fundamental particles are constantly winking in and out of existence. (It’s freaky to think that this is happening all around you all the time but it’s true.) Hawking realized that if a particle and its antiparticle appeared just at the edge of a black hole’s event horizon something odd would happen. Typically, these two particles would annihilate one another and release their energy back to the universe. But if one of the pair got sucked into the black hole, the other would get flung outward. The expelled particle would carry a bit of the black hole’s energy away, slowly sapping its strength. Given enough time, black holes would evaporate.

This introduced a dilemma: What exactly happens to that particle falling into the black hole? According to the laws of quantum mechanics, information about that particle cannot be destroyed. But once a particle has slipped beyond the event horizon, nothing about it, including its quantum mechanical information, can be recovered. Or at least, that’s what Hawking argued for more than 30 years, even going so far as to make a famous bet with physicist John Preskill in 1997 that the intense gravity of the black hole somehow overpowers the laws of quantum mechanics. But in 2004, Hawking had to concede that he was wrong. The work of other scientists, particularly string theorist Donald Marolf and physicist Juan Maldacena, showed incontrovertibly that there was no way to destroy quantum information and that it was actually leaking out of the black hole.

Despite the fact that everyone agreed on this conclusion, no one had any idea of exactly how it was happening. The result generated yet another intractable problem. The particle and antiparticle responsible for this whole mess were quantum mechanically entangled, which means that their properties are forever linked. Theoretical physicist Joseph Polchinski, working with Marolf and others, showed in 2012 that, in order for everything else known about black holes to be true, this quantum entanglement would have to be severed. Such a process is possible but violent. Disentangling the twins would generate a huge amount of energy right at the black hole’s event horizon. This energy would form a wall of blazing fire around the black hole, incinerating anything that came near.

Yes, we’re getting to the bit about Hawking’s recent proposal. Just hold on. Nothing about black holes is quick and easy.

The searing firewall solution has yet to be fully resolved in the physics community. Some believe it, some don’t. But even for those inclined toward the idea, it creates, you guessed it, another major problem. According to Einstein’s relativity, an astronaut falling into a black hole shouldn’t notice anything particularly different about the universe when s/he passes the event horizon. Getting incinerated certainly counts as “something peculiar going on here.” Scientists are faced with a choice: give up on Einstein and acknowledge that firewalls exist or give up on quantum mechanics and realize that information gets destroyed in a black hole.

A fanciful image of what the heart of a black hole might look like. Of course, new theories could change this view. Image: NASA/JPL-Caltech

In an attempt to thread the needle between the options, Hawking recently proposed to do away with something else: the event horizon. He instead suggests that physicists consider a much more nebulous term called the “apparent horizon” around a black hole. The apparent horizon works a lot like an event horizon, in that light beams inside of it can’t escape. They get stuck in a holding pattern, moving as fast as they can to stay in the same place, like the Red Queen in Alice in Wonderland. In this way, light and other information can get sort of “stored” in an apparent horizon but eventually find its way out.

The apparent horizon and the event horizon don’t entirely overlap. 1) Because a black hole can grow (by sucking in extra mass), its event horizon may move outward past its apparent horizon. 2) Or, by releasing Hawking radiation, a black hole can diminish, shrinking its event horizon inside of its apparent horizon. The entire concept is pretty strange, even to physicists, and seems to depend on the way that you decide to slice up space-time in your equations. In his latest paper, Hawking is saying that the apparent horizon is the only real thing, allowing scientists to ignore the event horizon and the firewall/Einstein problems arising there.

Using an apparent horizon actually solves one other problem, namely how information can escape from a black hole. Because the apparent horizon’s trap is only temporary, radiation can leave the black hole and carry information, albeit in a very scrambled and chaotic form.

So does that mean that black holes’ problems are done away with? Absolutely not! Firstly, it will take some time for the physics community to digest exactly what Hawking is suggesting. Already, some scientists are for it while others aren’t so sure. The one thing that can basically be guaranteed at this point is that physicists will eventually find some other mind-bending property of black holes that seems to contradict everything we thought before.

- - -

Adam is a Wired Science staff writer. He lives in Oakland, CA,
near a lake and enjoys space, physics, and other sciency things.

Man's Ancient Past: Neanderthal Genes Helped Modern Humans Adapt to the Cold

Image by erix! via Flickr

"Interestingly, while earlier studies have estimated that 1 to 4 percent of a modern,

non-African human’s DNA has Neanderthal origins, authors of the Science paper

found that about 20 percent of Neanderthal genes live on in modern humans.

The researchers believe additional research based on a larger sample size may

reveal that our extinct relatives contributed a much greater share to our genome

than previously thought."

Neanderthal Genes Helped Modern Humans Adapt to Cold

http://blogs.discovermagazine.com/d-brief/2014/01/29/neanderthal-genes-helped-modern-humans-adapt-to-cold/#.Uu7q5lAo7qBBy 

by Gemma Tarlach

January 29, 2014

You’ve heard that Neanderthal DNA lives on in the genes of many modern humans — now there’s evidence that it helped our early ancestors adapt to life beyond the tropics and subtropics of Africa.

As gene sequencing becomes increasingly sophisticated, scientists have been able to prove that early modern humans traveling out of Africa to Europe and Asia interbred with Neanderthals already established in those regions. As a result, most non-African humans today have at least some Neanderthal genes.

But, using new techniques to zero in on traces of Neanderthal DNA in modern humans, researchers found the genes were not distributed evenly.

No Balls About It

Neanderthal-origin genes are concentrated in areas of the modern human genome that regulate the appearance of skin and hair. This finding, researchers say, suggests the genes were beneficial to modern humans by giving them characteristics that helped them adapt to colder climates (like thicker body hair, for example).

Even more unexpected, scientists discovered certain areas of the modern human genome had no Neanderthal DNA. In particular, genes on the X chromosome and those concerning the testes had no Neanderthal origin. Researchers believe these segments of Neanderthal DNA in a male hybrid must have reduced his fertility and thus were not passed on to later generations.

Neanderthal DNA Today

To determine Neanderthal DNA distribution in the modern human genome, authors of today’s paper, published in Nature, used a method comparing known Neanderthal genetic patterns with samples from more than 1,000 modern humans to find archaic genetic material from our long-lost relatives that has survived in our species’ genome.

A separate paper, published today in Science, compared the Neanderthal genome with the genes of more than 600 modern humans and reached similar conclusions.

Interestingly, while earlier studies have estimated that 1 to 4 percent of a modern, non-African human’s DNA has Neanderthal origins, authors of the Science paper found that about 20 percent of Neanderthal genes live on in modern humans. The researchers believe additional research based on a larger sample size may reveal that our extinct relatives contributed a much greater share to our genome than previously thought.

Image by erix! via Flickr

Man's Ancient Past: Oldest Human Footprints Outside of Africa Found in UK

Figure 5. Photographs of Area A at Happisburgh. a. Footprint surface looking north-east. b. Detail of footprint surface. Photos: Martin Bates. (doi:10.1371/journal.pone.0088329.g005)

Oldest human footprints outside Africa found in UK

http://www.newscientist.com/article/dn25022-oldest-human-footprints-outside-africa-found-in-uk.html?utm_source=NSNS&utm_medium=SOC&utm_campaign=hoot&cmpid=SOC%7CNSNS%7C2013-GLOBAL-hoot#.UvofsCmYa9I

• 18:52 07 February 2014 by Andy Coghlan
• For similar stories, visit the Human Evolution Topic Guide

Footprints left by five prehistoric humans between 850,000 and 950,000 years ago have been discovered on a beach in Norfolk, UK – the oldest such prints found outside Africa.

The footprints came to light on the shoreline at Happisburgh last May after severe storm erosion wore away cliffs above. Of 49 footprints visible, 12 were analysed in great detail. Within two weeks, the prints had been washed away by the sea – but not before a research team carefully recorded them by merging multiple digital photographs of each print to create high-precision 3D images.

"We think there were at least two or three children among them," says Isabelle De Groote of Liverpool John Moores University, UK, a member of the study team. "Three prints came from a single individual who is taller, so we think it's a male. They may have been foraging along the coast of the river for aquatic resources and food."

Pioneering predecessor

De Groote and her colleagues say that these early Britons probably belonged to a species called Homo antecessor. This European hominin first appeared around 1.2 million years ago. Bones of H. antecessor found in Atapuerca, Spain, are similar in age to the footprints, and seem to match the projected size of the Happisburgh hominins.

Homo antecessor, dubbed "pioneer man", probably died out about 600,000 years ago in Europe. It was replaced by Homo heidelbergensis, often seen as the direct ancestor of both the Neanderthals and our species.

The Neanderthals had replaced H. heidelbergensis in Europe by about 400,000 years ago, and they were themselves replaced by our species in Europe about 40,000 years ago, says Chris Stringer at the Natural History Museum in London, who was also involved in the analysis of the new footprints.

Stringer says the climate 850,000 years ago was colder than it is now, so the individuals were at the northernmost limit of hominin settlement. "They were coping with conditions harsher than today, so maybe they had more body fat. Or did they wear clothing or make windbreaks, and did they have fire? We don't have evidence yet."

Twice as old

The researchers estimated the age of the prints from fossils of animals – such as giant elk – and plants in the sediment that are known to have died out later. Stone tools, hacked animal bones and other artefacts found nearby on the same beach in 2010 also tally with the age.

Together, these suggest that humans reached northern Europe 350,000 years earlier than previously estimated. There are, however, as yet no signs of human fossil remains at the site. "We hope we will find some human fossils to pin down who these people were," says Stringer.

At almost 1 million years old, the prints are more than twice the age of any other human footprints found in Europe. But older hominin footprints exist in Africa, where prints 3.5 million and 1.5 million years old have been found respectively at Laetoliin Tanzania and Koobi Fora in Kenya.

For more pictures click here

Figure 3. Photographs of Area A at Happisburgh. a. View of Area A and borehole HC from cliff top looking south. b. View of Area A from cliff top looking south. Photos: Martin Bates. (doi:10.1371/journal.pone.0088329.g003)

Figure 4. Photographs of Area A at Happisburgh. a. View of footprint surface looking north. b. View of footprint surface looking south, also showing underlying horizontally bedded laminated silts. Photos: Simon Parfitt. (doi:10.1371/journal.pone.0088329.g004)

Figure 7. Vertical image of Area A at Happisburgh with model of footprint surface produced from photogrammetric survey with enlarged photo of footprint 8 showing toe impressions. (doi:10.1371/journal.pone.0088329.g007)

Figure 9. Vertical image of Area A at Happisburgh. a. Model of footprint surface produced from photogrammetric survey showing the prints used in the analyses of footprint orientation and direction; b. Rose diagram showing orientation data for 49 prints; c. Rose diagram showing direction of movement for 29 prints. (doi:10.1371/journal.pone.0088329.g009)