Experts have provided the grisly goods to back up 17th-century accounts of cannibalism during the Jamestown colony's "starving time" — including a skull that shows signs of being chopped at and pried apart.

"Our team has discovered partial human remains before, but the location of the discovery, visible damage to the skull and marks on the bones immediately made us realize this finding was unusual," Bill Kelso, chief archaeologist of the Jamestown Rediscovery Project in Virginia, said in a news release issued Wednesday. Specimens from the Jamestown site were laid out during a Washington news conference.

Written accounts described acts of cannibalism during the winter of 1609-1610, when sickness, starvation and attacks from native tribes in the area put the two-year-old Virginia settlement to its sternest test. Scores of the colonists who crowded inside James Fort died that winter. One of the accounts described a husband who killed his pregnant wife and salted her flesh for storage and consumption. (The husband was executed for the crime.)

There was no reason to doubt the accounts, but in the course of their decades-long excavation, archaeologists were on the lookout for remains that might tell more of the story behind Jamestown's hardships. They found the evidence in the form of a partial human skull and other bones lying in a 17th-century trash deposit. Kelso enlisted the Smithsonian Institution's National Museum of Natural History to sort out the clues. Colonial Williamsburg and Preservation Virginia helped provide historical context.

'Jane of Jamestown'
Based on an analysis of the bones — including the skull and its teeth, as well as the size of a tibia and bone growth in a knee joint — experts determined that the remains came from a 14-year-old female, nicknamed "Jane." The isotopic distribution of elements in the bones suggested that she consumed a European diet of wheat and meat.

Carolyn Kaster / AP

Doug Owsley, division head for physical anthropology at the Smithsonian's National Museum of Natural History, displays the skull and a facial reconstruction for "Jane of Jamestown" during a news conference at the museum in Washington on Wednesday.

Carolyn Kaster / AP

Strike marks are seen on the skull of "Jane of Jamestown" at the National Museum of Natural History.

The grisliest findings were reflected in the wounds to the head: The chief of the museum's division of physical anthropology, Douglas Owsley, identified chops to the forehead and the back of the cranium to open the head. Knife cuts on the jaw and the cheekbone could have been made during removal of the flesh. Other markings suggest that the head's left side was punctured and pried apart.

The scientists' conclusion: Jane was butchered for her meat.

"She was almost certainly dead when she was cannibalized," Jim Horn, Colonial Williamsburg's vice president of research and historical interpretation, told NBC News. "The way the cuts are configured on the skull points to the fact that she was dead. if she was not, there would have been more signs of a struggle, and the marks would have been more irregular."

Based on the bone analysis and the disposition of the remains at the site, researchers believe Jane arrived in Jamestown in August 1609, just months before the crisis. She might have been a maidservant, or the daughter of a colonist. Chances are that she died in January or February of 1610, from either sickness or starvation, Horn said.

"The 'starving time' was brought about by a trifecta of disasters: disease, a serious shortage of provisions, and a full-scale siege by the Powhatans that cut off Jamestown from outside relief," he said in Wednesday's news release. "Survival cannibalism was a last resort; a desperate means of prolonging life at a time when the settlement teetered on the brink of extinction."

When Lord De La Warr and his relief party arrived in Jamestown in the spring of 1610, he ordered the "cleansing" of the ruined settlement. "It must have looked like a charnel house when he arrived," Horn said. That's probably how Jane's remains came to be deposited amid a trash heap in an abandoned cellar, he said.

Jane's legacy
Jamestown went on to become the Virginia Colony's capital from 1619 to 1699. In the late 17th century, the settlement was devastated by a series of fires. At the dawn of the 18th century, Virginia's capital was moved to Williamsburg, and old Jamestown faded away. Decades later, the descendants of Jamestown's settlers played their part in the creation of the United States of America.

Researchers have not matched up Jane's bones with a specific member of the Jamestown colony, and although DNA samples have been saved for future analysis, they say there's little hope of identifying modern relatives for comparative genetic testing. But the excavation continues, and Jane's remains provide graphic evidence of Jamestown's desperation.

Horn acknowledges that the story of Jane has a grisly fascination to it, but he says there's a broader significance as well. "It revolves around what it took to successfully establish European colonies in the New World," he told NBC News. "In the early phase of European colonization of the Americas, most colonies actually failed. They failed for the kinds of reasons that we discovered at Jamestown. ... Most colonies lasted no more than six to 12 months. What we're looking in the case of Jamestown is a remarkable story of survival and endurance."

More about Jamestown:

• 400-year-old seeds found in Jamestown
• 'New World' shows off a new Jamestown
• Colonial armor found in Jamestown pit

An exhibition that tells the story of Jane and the survival of Jamestown, England's first permanent settlement in America, is due to open May 3 at Historic Jamestowne in Virginia. Jane's bones will be put on exhibit temporarily, and eventually they will be "respectfully reinterred," Horn said. The facility has also produced a book and DVD on the subject, titled "Jane." However, details of the discovery have not yet been published in a peer-reviewed scientific journal.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Lauren Solomon / Nicholas Moore / iStockphoto

Researchers say that dogs' ability to digest starch was enhanced due to genetic changes that probably occurred in parallel with domestication thousands of years ago.

Like humans, dogs underwent genetic changes thousands of years ago to adapt to a diet with more starch, researchers report. They say the change suggests that the rise of agriculture and the domestication of dogs might have gone hand in hand — but it'll take further analysis to confirm the connection.

"All dogs studied have this change, which I'd say puts it at least a couple of thousand years back in time," lead author Erik Axelsson of Sweden's Uppsala University said in an email. "But we cannot prove that it coincided with the onset of agriculture. This is something we are continuing to work on now."

The genetic shift, reported in this week's issue of the journal Nature, emerged from a detailed, genome-wide search for differences between a group of 60 dogs and  a group of 12 wolves from around the world. Axelsson and his colleagues say this is the first such search ever done for dogs.

"Only some years ago, a study like this would have been impossible due to sequencing costs," Axelsson explained. "Now it is relatively cheap. We started this study late in 2009 — that is, these projects take time."

Co-evolution with humans
Dogs are thought to have diverged from their wolvish ancestors tens of thousands of years ago, helped along by their proximity to ancient humans. Some experts would even say that humans co-evolved with domesticated animals. Past research has shown that wild breeds such as silver foxes can be turned into docile doglike creatures over the course of just a few generations.

But what genetic changes accompanied domestication? That's what the dog-vs.-wolf comparison was all about: The international research team found 36 regions of the dog genome that showed signs of selective pressure, either because they were so different from the wolf genome, or because the genetic signature became so common among different breeds of dogs.

Nineteen of the regions had to do with nervous system function — for example, the ability to create new connections in the brain. "These findings support the hypothesis that selection for altered behavior was important during dog domestication," the researchers wrote. Other regions had to do with the binding between sperm and eggs, or anatomical structure.

Then there were 10 genes that related to starch digestion and fat metabolism. "We propose that genetic variants within these genes may have been selected to aid adaptation from a mainly carnivorous diet to a more starch-rich diet during dog domestication," Axelsson and his colleagues said.

The genetic changes enhanced a dog's ability to break down starch by secreting an enzyme known as amylase in the pancreas. Wolves don't secrete nearly as much amylase, and thus they don't tend to eat starchy foods.

Why dogs went for starch
Why would starch digestion play such a significant role in dog evolution? Researchers have previously suggested that dog domestication began when wolves were attracted to waste dumps near agricultural settlements in ancient times.

"A process of natural selection started in this new niche that favored wolves that were efficient at this process," Axelsson said. "Being an efficient scavenger included being less shy, so as not to waste energy on running away when humans approached. This idea is supported by our evidence of selection in nervous system development genes, as they are likely to have effects on behavior.

"A completely new piece to the puzzle is our finding of a more efficient starch digestion in dogs," he continued. "This could mean that efficient scavenging also included having an efficient system for processing starch. That is, only wolves that could make good use of the scarce and mixed leftovers survived to become the ancestors of dogs."

Axelsson noted that other researchers have seen signs of similar genetic changes in human populations, which apparently made it easier for ancient farmers to handle a starchier diet. "The change in humans is less obvious, which makes sense, considering we were omnivores rather than carnivores prior to the agricultural revolution," he said.

Thanks to the rapid advance of gene sequencing, similar studies can now be conducted not only for dogs, but for other domesticated animals as well. Axelsson and his colleagues conducted such a study relating to chicken domestication several years ago, and now that dogs have had their genomes done, cats can't be that far behind. "I would be surprised if people aren't working on that now," Axelsson said.

Axelsson said that he used to have a dog. ("Now, we have kids instead," he joked.)

"It definitely preferred meat, but would happily feast on, for instance, potatoes," Axelsson said. "This, by the way, is probably important to note — dogs still prefer meat, but during their evolutionary history it was crucial for their survival to adapt to a diet that included a lot of starch as well."

More about dog evolution:

• Dogs (not chimps) act most like humans
• Dogs and humans share DNA, thanks to viruses
• Gallery: How science measures up cats and dogs

In addition to Axelsson, the authors of "The Genomic Signature of Dog Domestication Reveals Adaptation to a Starch-Rich Diet" include Abhirami Ratnakumar, Maja-Louise Arendt, Khurram Maqbool, Matthew T. Webster, Michele Perloski, Olof Liberg, Jon M. Arnemo, Ake Hedhammar and Kerstin Lindblad-Toh.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

NGTV / Lion TV via PBS

UCLA Professor Jared Diamond has studied traditional cultures for decades, laying out his findings in the Pulitzer Prize-winning book "Guns, Germs and Steel" as well as "Collapse" and his just-published volume, "The World Until Yesterday."

In the wake of a high-wire "fiscal cliff" performance that wasn't exactly their finest hour, members of Congress would do well to learn a lesson from the tribes of New Guinea and the Amazon: Listen to your elders. At least that's the lesson passed along by UCLA Professor Jared Diamond, the author of "The World Until Yesterday: What Can We Learn From Traditional Societies?"

Diamond documented the reasons why European invaders overwhelmed less technologically advanced cultures in his Pulitzer Prize-winning book, "Guns, Germs and Steel: The Fates of Human Societies." He laid out cautionary tales of social breakdown in the follow-up book, "Collapse: How Societies Choose to Fail or Succeed." In his newly published book, Diamond draws upon his decades of research in far-flung locales to lay out lessons for us less traditional types.

"Tribes constitute thousands of natural experiments in how to run a human society," he told a capacity crowd Thursday night during the kickoff of his international book tour at Town Hall Seattle.

Diamond says the useful findings from those experiments run a wide gamut, from the benefits of multilingualism to the right way to carry a baby ("vertically upright, facing forward"). But one of his biggest themes has to do with the way older people are treated, or mistreated. He noted that a Fijian friend was shocked to see how often America's senior citizens are shunted aside by the younger generation. And although some traditional societies have their own quirks about dealing with the aged — for example, strangling them when they become a liability — Diamond agrees that American attitudes need an adjustment.

Penguin

"The World Until Yesterday" is the latest book from Jared Diamond, a geography professor at UCLA.

"The lives of the elderly constitute a disaster area of modern American society," the 75-year-old Diamond said in Seattle. "We can do better."

He'd like to see senior citizens restored to the roles they have always held in traditional societies, but in a modern-day context: for example, as baby-sitters in a world where both parents work, or as fonts for the kind of wisdom you can't get through a Web search. He'd even like to see age given more respect on Capitol Hill, where the median age is 57 in the House and 62 in the Senate. That was the theme of my interview with Diamond on Thursday. Here's an edited version of the Q&A:

Cosmic Log: How would traditional societies deal with something like the fiscal cliff? What advice can you give to Congress for dealing with the kind of gridlock that we've seen?

Diamond: "The unrealistic answer is to say that the only senators and House members who are permitted to vote on fiscal-cliff issues are those who are over the age of 70. That's not realistic. But the realistic idea is to say that we should give disproportionate weight to the opinions of older politicians who have experienced a much wider range of financial conditions than have the young members of Congress. That is to say, we should listen to people who have gone through the Great Depression, the bubbles of the '80s, the soaring interest rates of the '70s. They've seen a variety of conditions, whereas younger people have seen only recent conditions, and they don't realize that things can be different. That's what comes out of traditional societies. 

"Most traditional peoples talk about 'tribal elders.' The reality is that the leaders of traditional peoples are always the older people. And the reason is, it's good. They have lots of lifetime experience under very different conditions.

"The same also applies to modern societies: Sometimes I'm asked to talk to hedge-fund groups. I'm struck by the fact that most of the people are in their 20s or 30s. There may be a few people in their 40s, and maybe a couple in their 50s. When you look at the statistics, about half of all hedge funds fail within the first five years, although many of them do spectacularly well for a couple of years. The reason is, the whiz kids are very good at algorithms that make money under good conditions. But they don't realize that conditions can be very different, that there are tough conditions — soaring interest rates, financial setbacks. So they don't have the long perspective. That's an example of how a long perspective is necessary for financial policy, just as it is for governing, for deciding about war and peace."

Q: Is there any institutional reform that can do that, or is it beyond modern society to get back to those ways?

A: "It's not beyond modern society, because if you look around at different modern societies — and I'm talking about rich industrial societies — some of them give a lot more deference and weight to older people than do others. The United States is an extreme in this respect. We are perhaps the modern rich society that has the biggest cult of youth. For example, when was the last time you saw a commercial with an 83-year-old raising a bottle of Coca-Cola? The Coke ads are all about 25-year-olds. That's our cult of youth. But in Europe, there is much more deference given to older people. In China, even more. In Japan, too, and in Mexico and Italy. So there's an area where the United States, in its own self-interest, can learn from the experience of its older people."

Q: I'm struck by one of the comments that a House Republican made during the fiscal-cliff deliberations, complaining about the "sleep-deprived octogenarians" in the Senate. ...

A: "Sure, but the octogenarians have had 80 years to see the advantages of taxes. Taxes are an investment, they're not money taken away from you. They're your own money that's being used for long-term purposes. Our taxes are paying for roads, they're paying for schools, they're paying for armed forces, they're paying for inspectors, they're paying for regulators. The more we put in, the more we get out. Now, this is not to deny that every government wastes some tax money. Nobody has figured out how to spend taxes in a way that there's no waste. But the basic mindset is that taxes bring benefits. The longer you live, the more you see those benefits."

Q: Is there an analog to taxation that has worked for traditional societies?

A: "There is, but it's not until you get to medium-to-large societies. Small traditional societies of a few dozen to a few hundred people really don't have anything like taxation. Once you get to a society of a few thousand people, where there's a chief — big enough that you can't have a face-to-face discussion, but you've got to have a chief — chiefs practice an early form of taxation. They require that the commoners turn over a fraction of their agricultural products to the chief. Part of that is used to support their own lifestyle, and part of that is also held in reserve to redistribute to the commoners in a time of famine. One could say that that's a precursor to state government taxation."

Q: Are there other things on your short list of lessons that could help break the societal gridlock we see today?

A: "Another whole area that's open for discussion is the area of conflict resolution. The American system of conflict resolution in the courts is a system of determining right and wrong, with winners and losers. But in traditional societies, conflict resolution has a different goal. The goal is to achieve and maintain peace between people who are going to have to deal with each other for the rest of their lives. The society is small, so you know everybody. In the United States, a big society, if you have a traffic accident, the other person is likely to be someone you never saw before and will never see again. So who cares whether they're unhappy with the result? But the reality is that anybody who's been involved with the American civil or criminal justice system knows that its goal is not to achieve reconciliation. And the result is emotional agony, often for the rest of one's life.

"It's particularly sad when that agony involves divorcing spouses, or so often it involves brothers and sisters, or parents and children who end up suing each other in inheritance disputes. That's because when you use courts and lawyers, the goal is not to achieve emotional clearance, but the goal is to decide right and wrong. That is another big subject area we could happily talk about for a few hours."

Q: Another big subject area would be how to deal with the emotional scars left by the string of mass shootings we've seen lately. Are there any lessons that can be drawn from traditional societies addressing that issue?

A: "My one-liner there would be the balance between individual interests and communal interests. The United States' laws provide that if an individual wants a gun, that individual is going to have a gun, even if that is bad for society as a whole. Today I'm talking from Seattle, which is 100 miles from the Canadian border. Here we have a neighbor that is as affluent as the United States, but has a different balance — with much more emphasis on communal interests and much less interest on individual rights. Among other things, Canadians do not feel that everybody should exercise their God-given right to carry a gun."

Think there's enough in what Diamond says to get a discussion going? Feel free to weigh in with your comments below.

More from Jared Diamond:

• Bilingualism is good for the brain
• Why the Navajo have thrived
• How to prevent a pandemic
• Video: Corporations vs. collapse

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Long-ago lore still has the power to ignite modern-day controversies: Witness the tempests that were stirred up this year over the Maya calendar, the purported "Gospel of Jesus' Wife," a bone box linked to early Christians, a disputed dinosaur skeleton and the plan to clone a woolly mammoth.

It turned out that there was much more to each of these cases than met the eye. Or sometimes much less. Either way, we'll be hearing more about ancient mysteries in the year to come. Here's a status report on six of 2012's most controversial mysteries (and missteps) in the realms of archaeology, anthropology and paleontology.

Gospel of Jesus' Wife: Harvard historian Karen King stirred up a sensation in September with the unveiling of a papyrus that apparently quotes Jesus talking about "my wife." The claims quickly sparked questions about the murky origins of the papyrus, and the Vatican suggested that the controversial text was faked. Most other experts on textual analysis were similarly skeptical.

The Harvard Theological Review withdrew plans to publish a scholarly article about the papyrus in its January issue, and this month a spokesman for the journal said tests to authenticate the document were not yet complete. The Smithsonian Channel has delayed broadcasting a documentary on the find, pending further testing. Status: In limbo.

The Jonah box: In February, researchers announced that they used a camera-equipped robotic arm to study an ossuary, or funerary bone box, within a sealed underground tomb in Jerusalem. They said the box was engraved with a picture of a fish, as well as allusions to "Jonah" and resurrection. Their conclusion was that the inscriptions served as evidence that early Christians were buried in the tomb — but skeptics disputed that interpretation. Did the picture really show a fish, or was it an upside-down tower, or an urn? The controversy was stoked by the fact that the "Jonah box" team was also behind the even more hotly debated "Jesus Tomb" project a couple of years earlier.

Months later, the findings are still in dispute. One of the researchers behind the find is James Tabor, a religious studies professor at the University of North Carolina at Charlotte.  He says some experts have told him privately that they agree with his interpretation, but they're reluctant to speak out because of the acrimony surrounding the original reports. One expert who has voiced cautious support for the "Jonah and the fish" interpretation is Princeton Theological Seminary's James Charlesworth. (That support, too, has come under criticism.) Tabor acknowledges that more evidence is needed. "What we really need to do is enter the tomb and bring those ossuaries out. ... But that would have to be maybe next year," he said today. Status: In limbo.

Maya calendar: 2012's most publicized ancient mystery has to do with the Maya calendar, and the fact that Dec. 21 apparently marked the end of a series of cycles — including the 394-year baktun cycle as well as the 5,126-year "cycle of creation." Somehow, those calendrical cycles got mixed up with worries about the end of the world. Did the ancient Maya really think the cosmos would blink out of existence when the calendar ended? And if they did, why should we believe them?

Nothing happened on Dec. 21, other than some New Age-style celebrations of the new age. But the controversy did attract some extra attention for archaeological finds — including the discovery of a calendar workshop that clearly referred to dates beyond 2012, and an inscription that refers to the end of a calendar cycle in 2012, but not the end of the world. Status: Case closed.

Heritage Auctions via Reuters

An 8-foot-tall dinosaur skeleton is tied up in federal court proceedings.

Disputed dinosaur: You could argue that the world's hottest dinosaur fossil is currently in federal custody in New York. The 24-foot-long skeleton, nicknamed Ty, was said to come from a tyrannosaur-like species known as Tarbosaurus bataar. Fossil dealer Eric Prokopi sold it for more than $1 million in May, but experts claimed that the bones must have been smuggled out of Mongolia years earlier. Federal authorities seized the skeleton and filed criminal charges against Prokopi.

The civil and criminal proceedings yielded some surprises: Prokopi's lawyers said the skeleton was assembled from bones that were gathered up from various sources, leading to a new nickname: "Franken-saurus." Government prosecutors, meanwhile, said they have photos and forms to back up their claims that the dealer was "a participant in the black market" in Mongolia. Just today, Prokopi pleaded guilty to the smuggling charges and agreed to give up the dinosaur skeleton. That means Ty will eventually be sent back to Mongolia. Prokopi could be sentenced to up to 17 years in prison, but today's plea may win him leniency from the court. Status: Case essentially closed.

Pyramids on Google Earth: Researcher Angela Micol made a splash in August with claims that Google Earth imagery appeared to show pyramid-type structures in the Egyptian desert. She suggested that these were previously unknown sites — but it turns out that archaeologists have known about them for decades, and have studied them up close. The most intriguing formations are natural mounds, topped by structures that may have served as watchtowers and/or wells, said Italian Egyptologist Paola Davoli.

Another formation that Micol saw in the imagery is thought to be an oddly shaped natural butte. Micol told me in September that she was working with contacts in Egypt to get a closer look, but there haven't been any new revelations lately. Status: Case close to being closed.

Cloning a woolly mammoth: Is it really possible to bring the woolly mammoth back to life, tens of thousands of years after the species went extinct? It's highly doubtful, but Korean and Russian researchers are still trying. The project, unveiled in March, would involve recovering viable cells from a mammoth specimen pulled from the Siberian permafrost, implanting the cells' genetic material into an elephant egg, creating a cloned embryo, then transferring the embryo to an elephant womb for gestation. Each of those steps is fraught with difficulty — and the South Korea scientist in charge of the project is none other than Hwang Woo-Suk, who was disgraced several years ago in a scandal surrounding faked cloning results.

Last month, The Siberian Times reported that samples of mammoth bone marrow, hair, muscles and fat tissue were taken from Yakutsk to Seoul, to find out whether living cells could be extracted. Sources at the lab in Seoul did not respond to phone or email inquiries this week, but even if the cells turn out to be viable, don't expect to see a mammoth resurrection anytime soon. Russian researcher Semyon Grigoriev said it would be "years before we learn to choose the suitable cells or to re-create an extinct DNA molecule." Status: Case not yet closed. Or should that be, "not yet cloned"?

Dinosaurs ... and more: Science writer Brian Switek (a.k.a. @Laelaps) rounded up the year's top stories in paleontology at his "Dinosaur Tracking" blog, just before shifting over to Phenomena, National Geographic's new online science salon. In an email, he highlighted a few of his favorite stories:

"I was particularly interested by Nyasasaurus (confirming an earlier origin for dinosaurs), Yutyrannus (showing that feathers were not just for small dinosaurs) and mammal bones adding new evidence that dinosaurs may have been endothermic," he told me. "In other fossil news, the two that jump to mind are: fossil turtles caught in the act of mating; and a new fossil shark species which shows that Carcharocles megalodon was not a giant ancestor of today's white shark, but a member of a different lineage altogether."

I've included the fossil turtle-sex tale in our annual roundup for the Weird Science Awards, but here are 30 more ancient mysteries that should keep you clicking into the new year:

Ten top paleontology tales from Cosmic Log and NBC News:

• Earliest-known dinosaur to walk the earth identified
• Four-winged flying dinosaur sported glossy black feathers
• Paleontologists find the king of the feathered dinosaurs
• Researchers re-create the love song of the Jurassic katydid
• This mammal-like predator reigned long before the dinosaurs
• Methane-emitting dinosaurs could have warmed the earth
• World's oldest panda fossils found, and not in China
• Researchers decide to downsize the dinosaurs
• Scientists say dinosaurs' feathers were meant for mating
• Ancient lizard that died with the dinos is named after Obama

Ten top anthropology tales from Cosmic Log and NBC News:

• New technique clears up Denisovan DNA mysteries
• Australopithecus sediba: This pre-human ate like a chimp
• Cave art is so old the Neanderthals could have done it
• Hunter-gatherers were 'friending' long before Facebook
• Ancient Lucy's kin could have swung from the trees
• Researchers reconstruct the real-life face of a 'Hobbit'
• Foot bones could help reveal origins of upright walking
• Tools suggest early humans were smarter than we thought
• New flat-faced human species possibly discovered
• China's Red Deer Cave People may have been different species

Top 10 discoveries from Archaeology magazine:

• Maya sun god masks (more from Brown University)
• Neanderthal medicine chest (more from Cosmic Log)
• First use of poison (more from LiveScience on NBC News)
• Aztec ritual burial (more from Discovery News)
• Caesar's Gallic outpost (more from LiveScience on NBC News)
• Europe's oldest engraving (more from Discovery News on NBC News)
• First pots in China (more from Harvard University)
• Scottish 'Frankenstein' mummies (more from LiveScience on NBC News)
• 2,000-year-old stash in Israel (more from LiveScience on NBC News)
• Oldest Egyptian funerary boat (more from Ahram Online)

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

MPIEA

Ancient DNA was extracted and analyzed using a novel sequencing approach.

Degraded DNA molecules from a group of human relatives who went extinct tens of thousands of years ago have been reassembled using a new technique, yielding a genetic code for the mysterious Denisovans that meets the standard for modern humans.

The findings are based on samples drawn from 40 milligrams of ground-up bone from a Siberian girl's finger. They confirm what scientists saw in a much less detailed genetic sequence they produced a couple of years ago, and address some of the deep questions surrounding the Denisovans. But they also raise a few new questions, including a basic one: Just how old was the sample they analyzed?

"The amazing thing is that we can sequence the whole genome to very high accuracy, but there is too little carbon in it to do a date," Svante Pääbo, a genetic researcher at the Max Planck Institute for Evolutionary Anthropology, told reporters during a teleconference this week. Pääbo is the leader of the research team behind a paper on the project, published online today by the journal Science.

The finger bone was found in southern Siberia's Denisova Cave during an excavation in 2008. That dig was aimed at untangling the genetic relationship between Neanderthals and modern humans, and bones representing both those species were indeed found in the cave. But the initial analysis of the finger-bone sample revealed a genome that was neither Neanderthal nor classically human. That tiny bone and two molars that were also found in the cave represent the only known specimens of the Denisovan race.

MPIEA

A replica of the Denisovan girl's finger bone sits on a pinky finger, providing a sense of scale.

Previous analyses of the Denisovan genome were considered merely a rough draft, doing no better than an average of 1.9 readings for every molecular base pair in the DNA, or 1.9X. In comparison, the latest analysis goes to a coverage depth of 30X, which is typical of whole-genome sequencing for present-day humans.

The accuracy was increased by taking short, degraded double-strands of DNA, which couldn't be analyzed  the usual tools for gene sequencing, and "unzipping" them into single strands. That made it easier to attach specially designed molecules known as adapters and read out the DNA code, piece by piece.

"There are many things you can do with such a high-coverage genome that you cannot do with the low-quality genome that we had before," said Matthias Meyer, a colleague of Pääbo's at the Max Planck Institute who developed with the new sequencing technique. Here are the main findings reported today:

• A comparison of chromosomes that the girl inherited from her mother and father indicated that there was surprisingly low genetic diversity in the Denisovan population. That would suggest that the Denisovan population never was very large, and could explain why the group faded into extinction as populations of modern humans spread out. The analysis also confirms that the girl carried genes that have been associated with dark skin, brown hair and brown eyes. "It is very likely that they were dark-skinned, and that is really everything we can say about that," Pääbo said, "The truth is, of course, that one can say quite little about how people looked from just studying the DNA sequences." 
• Detailed study of the "gene flow" over time suggests that the Denisovans interbred with Neanderthals as well as our own species, Homo sapiens. The analysis confirmed previous findings that Denisovans were more genetically similar to Neanderthals than to anatomically modern humans. So does that mean that Denisovans were a separate species? "I really stay away from species designation," Pääbo said. "I would not call it a different species, but clearly different groups with a different history. I would not call the Neanderthals a different species from humans either, actually."
• A comparison of the genome with those of modern-day human populations confirmed that Melanesians, Australian Aborigines and other Southeast Asian islanders had the most in common genetically with the Denisovans. The Denisovan contribution to the genomes of present-day Papuans was estimated at 6 percent.
• A deeper analysis of the Papuan-Denisovan connection showed that the Denisovan contribution was lower for the sex-linked X chromosome than it was for other chromosomes. That might suggest that the Denisovan males were more likely than the females to interbreed with modern humans. Or it could mean there was a genetic defect on the X chromosome that led to its elimination from modern-day genomes.
• The researchers were able to triangulate, using the Denisovan genome as well as the genetic codes for Neanderthals and modern humans, to come up with an unexpected result: Present-day east Asians and Native Americans appear to have more in common genetically with the Neanderthals than present-day Europeans, even though Europe was thought to be the main hangout for Neanderthals hundreds of thousands of years ago.
• The researchers also drew up a catalog of more than 100,000 genetic differences that apparently arose between modern humans and the now-extinct Denisovans and Neanderthals in the past 100,000 years or so. About 260 of the changes affect protein function, Pääbo said. "It's quite interesting to me to note that eight of them have to do with brain function and brain development — the connectivity in the brain, how synapses between nerve cells function. And some of them have to do with genes that, for example, can cause autism when these genes are mutated," he said. "I think this is perhaps in the long term, to me, the most fascinating thing about this: what it will tell us in the future about what makes us special in the world, relative to Denisovans and Neanderthals."

Genetic sequencing alone can't tell scientists how long ago the Denisovans lived, however. Pääbo and his colleagues factored in assumptions about the mutation rate of the human genome to estimate that the girl with the finger bone lived somewhere around 74,000 to 82,000 years ago. But a separate line of evidence, based on the rock layering in the cave, suggested that the bone was 30,000 to 50,000 years old.

"I'm very unsure about the archaeological dates, but I would say I'm equally unsure about our molecular dates," Pääbo told reporters.

Similarly, the researchers give a wide range of dates for their estimate of the time when the Denisovan population split off from the evolutionary line leading to modern humans: 172,000 to 700,000 years ago.

"Most of the uncertainty in that number ... comes from the uncertainty at present about the human mutation rate," said another co-author of the paper, David Reich, a geneticist at Harvard Medical School and the Broad Institute. "There is a lot of debate in the community about the rate at which mutations accumulate."

Future studies, involving DNA analysis as well as carbon-dating analysis of other specimens from the Denisova Cave, may help clear up that uncertainty. But for the team behind the research announced today, an even higher priority is to generate a gene sequence for the Neanderthals that's as good as the sequence they now have for the once-mysterious Denisovans.

John Hawks, an anthropologist at the University of Wisconsin at Madison, said the newly published paper was "solid work."

"It's really neat that they've organized a catalog of things that humans have that are not present in this ancient genome," Hawks, who studies human origins but was not part of Pääbo's research team, told me. He said the study of comparative brain genetics, for example, was becoming an increasingly important area, "and this study is part of it."

"We know that the human brain is a big target of evolution, but establishing the order of these changes is an important step now," he said. "This gives us a time stamp on some of those changes."

The technique developed for the Denisovan DNA could be applied much more widely in the future. Meyer said his method could be used on modern-day forensic samples that are too degraded to be analyzed using current techniques. And who knows? Anthropologists may find still more long-lost, extinct cousins in the fossil record whose genomes need to be done.

More about our human and near-human relatives:

• Fossil DNA points to new branch of humanity
• Ancestors had sex with mysterious human cousins
• How sex with Neanderthals and Denisovans made us stronger
• Did previously unknown type of human live in Chinese caves?

In addition to Pääbo, Meyer and Reich, authors of the Science paper, "A High-Coverage Genome Sequence From an Archaic Denisovan Individual," include Martin Kircher, Marie-Theres Gansauge, Heng Li, Fernando Racimo, Swapan Mallick, Joshua G. Schraiber, Flora Jay, Kay Prüfer, Cesare de Filippo, Peter H. Sudmant, Can Alkan, Qiaomei Fui, Ron Do, Nadin Rohland, Arti Tandon, Michael Siebauer, Richard E. Green, Katarzyna Bryc, Adrian W. Briggs, Udo Stenzel, Jesse Dabney, Jay Shendure, Jacob Kitzman, Michael F. Hammer, Michael V. Shunkov, Anatoli P. Derevianko, Nick Patterson, Aida M. Andrés, Evan E. Eichler, Montgomery Slatkin and Janet Kelso.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

M. Hofreiter / K. Fiusterweier

Researchers say some Neanderthals may have had pale skin and red hair similar to that of some modern humans. Explaining the genetic similarities, however, can lead to a tangled tale.

One of the most titillating tales in the study of human origins — focusing on whether Neanderthals interbred with modern humans — has just gotten more tangled.

Over the past couple of years, studies of Neanderthal DNA samples painstakingly extracted from ancient bones have suggested that contemporary non-Africans can trace up to 4 percent of their genetic code to our long-extinct Neanderthal cousins. The genomes of modern-day Africans, in contrast, have virtually nothing in common with the Neanderthals. Researchers assumed that the genetic contribution for the non-Africans was passed down through cross-species sex during the time that Neanderthals and Homo sapiens lived in close proximity in Europe, tens of thousands of years ago.

However, there's another possibility: Maybe that common genetic code was passed down from the common ancestor of Homo sapiens and Homo neanderthalensis, hundreds of thousands of years ago in Africa. Today, researchers at the University of Cambridge reported in the Proceedings of the National Academy of Sciences that such a scenario provides a better fit for the genetic data. They say there's no need to assume that anatomically modern humans did the Neanderthal nasty, a process known more scientifically as hybridization. 

"Our work shows clearly that the patterns currently seen in the Neanderthal genome are not exceptional, and are in line with our expectations of what we would see without hybridization," the lead researcher, Andrea Manica, said in a Cambridge news release. "So, if any hybridization happened — it's difficult to conclusively prove it never happened — then it would have been minimal and much less than what people are claiming now."

Modeling population dynamics
Manica and his colleagues set up a computer model for the last half-million years of population dynamics, with the assumption that there were two migrations from Africa. The first migration led to the settlement of Europe by the ancestors of the Neanderthals, hundreds of thousands of years ago. Then, around 300,000 to 350,000 years ago, the route from north Africa to Europe was cut off somehow. The European and north African populations showed gradual genetic divergence, but still retained a bit of common heritage from their mutual ancestors.

When the second migration from Africa took place, around 60,000 to 70,000 years ago, the north Africans who dispersed to Europe and Asia would carry that extra bit of genetic similarity with them. But the Africans who lived farther south and stayed behind on the continent wouldn't have as much genetic kinship with the Europeans.

The researchers found that their model did a fine job of accounting for the existing data without Neanderthal sex.

So what do the researchers behind the earlier DNA studies say? That's where it gets really interesting: One study, published online in April in Molecular Biology and Evolution, contends that ancient population dynamics alone can't account for the genetic patterns seen in the DNA from Neanderthals and modern humans. Another study, posted on the arXiv preprint server and due for publication in PLOS Genetics, takes a closer look at a genetic pattern known as linkage disequilibrium — and concludes that modern humans and Neanderthals interbred somewhere between 37,000 and 86,000 years ago. Nature's Ewen Callaway delves into the details surrounding those claims and counterclaims.

Either-or proposition?
So, to recap: Some scientists say the population dynamics that were in effect hundreds of thousands of years ago can explain genetic similarities between populations, even if those populations never interbred. Others say the evidence is getting stronger that modern humans and Neanderthals really did mate when they met up in Europe, tens of thousands of years ago.

University of Washington geneticist Joshua Akey says both sides just might be right.

"To me, I don't think it's a case of either-or," he told me. "I think that both things can be going on."

Akey and other researchers recently published a study in the journal Cell suggesting that a mysterious "Neanderthal sibling species" made a genetic contribution to the DNA of modern-day Africans. He said that interpreting whether genetic similarities come from a common ancestor (a process known as archaic population structure) or from more recent cross-species sex (a process that Akey calls introgression) is a tricky but essential task for those who study human origins.

"Ultimately, it's important that we come to a consensus as to one process or the other, but I find them both to be interesting interpretations," Akey said. "Introgression is a sexier mechanism, but even if it turns out to be a case of archaic population structure, that still tells us something about our past that we didn't know before."

So did modern humans do it with Neanderthals or not? And to what extent? Today, maybe it's a tangled tale, but that won't necessarily be the case forever. Akey said he was optimistic that researchers will be able to "tease apart" the different influences from the two processes within the next year or so.

Update for 2:10 a.m. ET Aug. 14: In a follow-up email, Akey clarified his view on the "did they do it" question, leaning toward the affirmative:

"Although I do think that both ancestral population structure and introgression are not mutually exclusive events, the recent papers from David Reich and Monty Slatkin show pretty compelling evidence that introgression of Neanderthal lineages into anatomically modern humans occurred. Thus, the real debate moving forward will be about the relative contributions of these two processes."

More about ancient hominid sex:

• Neanderthal-human sex rarely produced kids
• Ancestors had sex with mysterious human cousins
• How sex with Neanderthals made us stronger

Cambridge's Anders Eriksson is Manica's co-author on the paper published by the Proceedings of the National Academy of Sciences, titled "Effect of Ancient Population Structure on the Degree of Polymorphism Shared Between Modern Human Populations and Ancient Hominins."

Authors of the study in Molecular Biology and Evolution are Melinda Yang, Anna-Sapfo Malaspinas, Eric Durand and Montgomery Slatkin.

Authors of the preprint destined for PLOS Genetics are Sriram Sankararaman, Nick Patterson, Heng Li, Svante Pääbo and David Reich.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the dwarf planet and the search for new worlds.

Researchers used a clever trio of tricks to figure out what 2 million-year-old human ancestors ate by analyzing the stuff on their teeth, and they found something unexpected: They ate more like chimpanzees than like humans. Their analysis could point to a reason why our species triumphed while some of our long-lost cousins failed.

"Our results suggest that there was more variation among hominins around 2 million years ago, in terms of what they ate and where they lived," Amanda Henry of Germany's Max Planck Institute for Evolutionary Anthropology explained in an email, using the technical term for humans and their close fossil relatives.

The various species spread out into different environments, ranging from forests to grasslands, but each species had a preferred environment, in part due to diet specialization. "Then, with the evolution of Homo erectus around 1.8 million years ago, we see a big shift," Henry said. "Homo erectus thrived in a whole variety of environments, and was even able to migrate out of Africa."

Homo erectus eventually gave rise to Homo sapiens — that is, us. Meanwhile, the hominins that were tied down to Africa's forests — perhaps including Australopithecus sediba, the South African species that Henry and her colleagues studied — faded away in the competition with other apes. The latest research, published online today by the journal Nature, doesn't address that big evolutionary issue directly. But it does provide plenty of food for thought.

Decoding the diet
Australopithecus sediba was discovered in 2008, and has come to be seen as a transitional species between the relatively small, ape-like pre-humans known as australopiths and our closer ancient relatives in the genus Homo. Only a few specimens of the species have been recovered, but they appear to reflect chimp-like as well as human-like characteristics.

So which way did Au. sediba swing when it came to its diet? The researchers focused on the teeth of two specimens, a juvenile male and an adult female.

First, the researchers zapped the tooth enamel with a laser and analyzed the vapor that was given off. The composition of the enamel preserves a record of what the individual ate while it was growing up. In this case, Johns Hopkins University geochemist Benjamin Passey used a mass spectrometer to look at the balance of carbon-12 and carbon-13 isotopes in the vapor.

Lee Berger

The teeth of a juvenile male Australopithecus sediba had a dark layer of calculus, which is clearly visible in this close-up picture.

If the level of carbon-12 is relatively high, that suggests a diet heavy in forest products such as leaves, fruits and the critters that eat those things. Those are known as C3 foods. But if carbon-13 is high, that points to foods from the African savanna, such as seeds, roots and grasses. These are C4 foods.

"It seems like a hallmark of human evolution to be able to use savanna resources," Passey told me. "Today, most of our energy comes from grass in one way or another, either from grain or from animals that eat grain and grass."

Tests on sediments and various animal bones suggested that the area where the specimens were found was a savanna 2 million years ago. However, when Passey analyzed the samples from Au. sediba, he found that the carbon was almost pure C3, suggesting a diet heavy in forest products.

Two other lines of evidence confirmed that preference: Deposits of plaque on the teeth contained bits of silica, known as phytoliths, that were linked to forest vegetation. Also, the pits on the teeth were characteristic of creatures that favored a forest diet. All the evidence pointed to the conclusion that these particular pre-humans went to the forests for virtually all of their food, even though their remains were left behind in the savanna.

"This astonished us," Passey said.

The meaning of diet
Upon reflection, it shouldn't be that surprising that Australopithecus sediba passed up what the African savanna had to offer, said the University of Colorado's Matt Sponheimer, another co-author of the Nature paper. "We know living apes don't seem to like such foods much — or at least they are never a large portion of their diets," he told me in an email. "It is likely that this is at least partly due to their masticatory (and probably digestive) anatomy being suboptimal for such diets."

Modern-day savanna chimpanzees engage in similar behavior, the researchers noted.

The findings are consistent with the view that "early hominins were quite flexible with respect to diet, with different populations preferring different parts of the available plant resource base, depending on when they lived, and where," said Bill Kimbel, who serves as director of Arizona State University's Institute of Human Origins but was not involved in the Nature study. "The plant phytoliths are a nice addition to the repertoire of perspectives on the issue."

In an email exchange, Kimbel cautioned against reading too much into Au. sediba's preference, as reflected by the results from two individuals. He took issue with my suggestion that the results put the species in the "chimp camp" rather than the "human camp," and noted that other hominin species had different preferences for C3 vs. C4 foods.

"I don't think sediba should be seen as 'remarkable' in this context," he told me. "And sediba no more belongs in the 'chimp camp' than it does in the 'giraffe camp' (with which it also shares dominant C3 values). This is not a useful analogy."

Sponheimer declined to say whether he thought Australopithecus sediba died out because it didn't shift its diet to the foods of the savanna, "but one could make such an argument if indeed this was an organism tied to very specific microhabitats by a limited dietary repertoire." A different argument could be made as well: Perhaps the descendants of Au. sediba eventually adapted to a diet that took in C4 as well as C3 foods, and thus contributed to the rise of early Homo.

Passey, for one, would love to study more specimens. "It would be nice to analyze those and see if all members of that species have that same forest behavior," he told me. However those future experiments turn out, the findings reported today show how novel techniques — ranging from precision laser blasting to tooth-crud analysis — can shed light on the origin of our species.   

More about human origins:

• Was there a fork in our family tree?
• Humans had sex with now-extinct relatives
• Fossils shake up humanity's family tree
• Savannas may have nurtured human ancestors

In addition to Henry, Sponheimer and Passey, the authors of "The Diet of Australopithecus Sediba" include Peter S. Ungar, Lloyd Rossouw, Marion Bamford, Paul Sandberg, Darryl J. de Ruiter and Lee Berger. The paper, published online today, will appear in a future print edition of Nature.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Rhett A. Butler / mongabay.com

New evidence challenges the idea that the Amazon Basin was densely inhabited before the arrival of Europeans.

The historical portrayal of the Amazon Basin's residents before 1492 has swung from the stereotype of backward savages to a vision of sophisticated stewards of the land — but a newly reported survey suggests that wide swaths of the Amazon's forests, particularly in the western and central regions, were relatively untouched by humans.

The findings could play into the debate over the Amazon's future as well as its past.

""You can't use an idea of past transformed landscapes to justify modern deforestation," Crystal McMichael, a paleoecologist who analyzed Amazonian soil as part of her research at the Florida Institute of Technology, told me. McMichael is the lead author of a study published in today's issue of the journal Science.

She and her colleagues collected 247 core samples of soil from 55 sites throughout the central and western Amazon, in Brazil and Peru, to check for signs of human disturbance. Their objective was to provide a reality check for what some researchers have called the "1491 hypothesis": the idea that areas of the Amazon Basin were intensely managed centuries ago, but reverted to a more natural state after the arrival of explorer Christopher Columbus and his European brethren, due to the decline of indigenous culture.

One of the foremost critics of that view is Dolores Piperno, a senior scientist at the Smithsonian Institution's National Museum of Natural History and the Smithsonian Tropical Research Institute. Piperno is a co-author of the Science paper.

"Drawing on questionable assumptions, some scholars argue that modern Amazonian biodiversity is more a result of widespread, intensive prehistoric human occupation of the forests than of natural evolutionary and ecological processes," she said in a Smithsonian news release. "Climatologists who accept the manufactured-landscapes idea may incorporate wholesale prehistoric Amazonian deforestation, widespread fires and carbon emissions into their models of what caused past shifts in atmospheric carbon dioxide and methane levels. But we need much more evidence from Amazonia before anything like that can be assumed."

The evidence from the soil samples, including samples taken from sites with previously known human impacts, runs counter to those assumptions. Most of the samples showed little sign of charcoal, which would have been left behind by land-clearing fires. There were few signs of silica deposits known as phytoliths, which are indicators of ancient agriculture. The researchers did pick up the signature of "terra preta" — that is, earth enriched by human waste — but mostly around riverbanks rather than far into the forest.

Crystal McMichael

Researchers Crystal McMichael and Monica Zimmerman collect soil samples in the tropical rainforests of Peru.

"Together, the data suggest that human population densities in the sampled regions were low and highly localized, and were not consistent with major population centers with associated areas of widespread, extensive agriculture," the researchers wrote.

The findings came as no surprise to Michael Heckenberger, an anthropologist at the University of Florida. Heckenberger is perhaps best-known for his study of ancient urban communities in the Upper Xingu region of the Brazilian Amazon, east of the areas surveyed by McMichael and her colleagues. His work was discussed in "The Lost City of Z," a best-selling book by David Grann.

"I was delighted to see the paper, because it does act as a cautionary note," Heckenberger told me. 

Heckenberger said the research fits in with the view that the pre-Columbian Amazon Basin had wide areas of forest land that showed relatively little human alteration, as well as areas that supported substantial concentrations of human population.

"This clearly has moved the debate forward," he said. "I hope we don't digress back to [a debate over whether] the Amazon was the setting par excellence for primordial forests and primitive tribes vs. an area that was dominated by large, complex societies. It's neither one nor the other. ... There were patches of dense, complex societies, and then there were other areas that were, if not completely untouched, then something very like untouched forest."

Heckenberger said he was "still of the opinion that as time progresses, we're going to find more and more of the Amazon that did support large populations." But he praised the work published in Science and said he hoped to see more sampling of sites from broader stretches of the Amazon Basin.

"I'd love to grab that team and bring them to my research site, to use that to some degree as a control against what you might expect," he told me. "The flip side of that is to jump into the pickup truck with that team and look for archaeological signatures in the area that they've been studying."

McMichael thought that was a fine idea. "He's done some excellent work," she said of Heckenberger.

She speculated that pre-Columbian tribes preferred to live near rivers rather than in the forest interior "so they could connect with other communities" more easily. She also suspected that the eastern side of the Amazon Basin was settled more intensely than the western side because it was drier and more amenable to forest-clearing. However, even if large settlements existed in some parts of the Amazon before Columbus, that shouldn't be used as a defense for 21st-century deforestation, McMichael said.

"The amazing biodiversity of the Amazon is not a byproduct of past human disturbance," she said in a news release. "We also can't assume that these forests will be resilient to disturbance, because many have never been disturbed, or have only been lightly disturbed in the past. Certainly there is no parallel in western Amazonia for the scale of modern disturbance that accompanies industrial agriculture, road construction, and the synergies of those disturbances with climate change."

More about Amazonian culture:

• Pre-1492 Amazon farmers didn't use controlled burns
• How the Amazon's lost cities worked
• Another 'Stonehenge' discovered in Amazon
• Gallery: A tale of seven cities, lost and found

In addition to McMichael and Piperno, authors of "Sparse Pre-Columbian Human Habitation in Western Amazonia" include M.B. Bush, M.R. Silman, A.R. Zimmerman, M.F. Raczka and L.C. Lobato.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

HBO

A freshly hatched dragon perches on the shoulder of Daenerys in "Game of Thrones."

This the Year of the Dragon, and not just because of the Chinese calendar: Dragons play big roles in HBO's "Game of Thrones" TV series as well as the upcoming film version of "The Hobbit." Those fire-breathing, leathery-winged reptiles have been gripping the human imagination with their sharp talons for millennia, and it's worth wondering why.

Some folklorists trace the dragon myth back to a variety of sources in ancient China, Rome, Greece and India, and speculate that it had its genesis in the discovery of fossil bones from the strange creatures we now know as dinosaurs:

• Scythian lore described griffins with lionlike bodies and birdlike beaks. In the year 77, Pliny the Elder passed down the Scythian stories of gold-guarding griffins with peculiar ears and wings.
• During his travels in northern India, the first-century Greek philosopher Apollonius of Tyana reported that "no mountain ridge was without" a dragon to its name. The locals said they used magic to lure the dragons out of the earth and pry out the gems embedded in their skulls.
• Chinese accounts of "dragon bones" go back thousands of years — and as recently as 2006, ground-up dinosaur bones were being used in traditional medicine by villagers who believed they came from dragons. (The hard-to-crack dragon eggs depicted in "Game of Thrones" may well trace their lineage back to fossilized dinosaur eggs.)

Classical folklorist Adrienne Mayor, who relates all these tales in her book "The First Fossil Hunters," ascribes the reports to discoveries in fossil-rich regions such as the Altai Mountains in Central Asia, the Gobi Desert in China and Mongolia, or the Siwalik Hills in the Himalayas. Not knowing any better, adventurers interpreted the dinosaur bones as representing the remains of dragons, griffins and other mythical monsters.

The gold hoarding? That may have arisen because gold deposits were found close to the fossil beds along ancient Issedonian trade routes.

And the gems? "I think the Indian lore about special gems prised out of dragon skulls alludes to the crystals that can form on mineralized bones," Mayor wrote. "The detailed observations of the first modern investigator of the Siwalik fossils confirm my theory: large, glittering calcite crystals and tubular selenite crystals are common in the Siwalik fossils."

Hard-wired for dragons?
Anthropologist David Jones went even further in his book "An Instinct for Dragons," published in 2000: He proposed that the fables about winged, poison-spewing, fanged and clawed creatures combined three of the top threats to ancient pre-human primates: raptors like the one that may have preyed on a now-fossilized ape-boy known as the Taung child nearly 2 million years ago; poisonous snakes like the ones that may have driven the evolution of big brains and improved vision in primates millions of years ago; and big cats like the ones our pre-human ancestors had to watch out for in Africa.

"The world-dragon was formed by the nature of our own shadowy progenitors' encounters with the creatures who hunted them over millions of years," Jones wrote. The way he sees it, our brain came to be hard-wired with an instinctive fear of dragons.

Paul Jordan-Smith, a folklorist and storyteller who wrote a fiery critique of Jones' book for the journal Western Folklore, thinks the idea that our ancestors somehow evolved a dragon instinct just doesn't hold up. For one thing, Jones' claim that multiple cultures had the same conception of dragons as dangerous beasts is "demonstrably untrue," he said.

"My take on the mythic image of the dragon is that there is no one 'authentic' image, and no one 'true' meaning," Jordan-Smith told me in an email. "The dragon has been a guardian, a thief, a hoarder (like Smaug, in 'The Hobbit') and a dispenser of wisdom (especially in Chinese tales)."

For another thing, the dragon doesn't show up fully formed in ancient tales.

"It's interesting that dragons do not appear in cave paintings," Jordan-Smith wrote. "What does appear are the beasts that they hunted or that were dangerous. ... Where you do see constructs that aren't literal depictions, they're of humans merged with animals. And when you get civilization, you don't see dragons until much later. ... You don't get dragons until you get stories that have dragons in them."

Who's gripping whom?
But once dragons become part of a culture's mythic milieu, they don't fade away. Perhaps that explains why dragons hang around, in Chinese New Year festivals, in European fairy tales, and in American movies and TV shows. Here's what Jordan-Smith had to say about that:

"A dragon, like most mythic imagery, is 'plastic,' in the sense of being adaptable. It can look like whatever the singer of tales wants it to, can serve whatever purpose needed, and can mean just about anything. And some of the traditional qualities may not be incompatible with one another. A dragon that guards a treasure (or an abducted maiden) may be waiting for the right hero that will liberate it from its responsibility. A dragon that threatens to destroy a village may be a wake-up call to rectify misdeeds. Some dragons are enchanted and must be slain to regain their true form. But not all dragons are meant to be slain.

"And what of the hero? He must be changed somehow by the encounter, or else the game is not worth the candle. But what kind of change? In some cultures, to slay a fearsome beast was tantamount to assimilating its powers. ... In Tolkien's books, the Ring exerts its power so thoroughly that its wearer little by little becomes like Gollum. Perhaps there's a particular kind of danger, much more deadly than merely being killed. And perhaps when the hero slays the dragon, he himself is slain, to be reborn as the human incarnation of the dragon. For good or ill? Ask the storyteller."

Maybe it's not the dragon that has a grip on us. Maybe we're the ones who are hanging onto the dragon — and we don't want to let go.

More about dragons and 'Game of Thrones':

• Origin of Komodo dragons revealed
• Chinese villagers ate dinosaur 'dragon bones'
• Sword science plays a role in 'Game of Thrones'
• All about 'Game of Thrones' on The Clicker

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

Coren Apicella

A woman from Tanzania's Hadzabe tribe studies a social-networking chart.

Hunter-gatherers exhibit many of the "friending" habits familiar to Facebook users, suggesting that the patterns for social networking were set early in the history of our species.

At least that's the conclusion from a group of researchers who mapped the connections among members of the Hadza ethnic group in Tanzania's Lake Eyasi region. The results were published in this week's issue of the journal Nature.

"The astonishing thing is that ancient human social networks so very much resemble what we see today," senior author Nicholas Christakis, a sociologist at Harvard Medical School, said in a university news release. Researchers from Harvard, the University of California at San Diego and Cambridge University worked together to document the Hadza's social networks.

"From the time we were around campfires and had words floating through the air, to today when we have digital packets floating through the ether, we've made networks of basically the same kind," Christakis said.

Another co-author of the study, UCSD's James Fowler, said the results suggest that the structure of today's social networks go back to a time before the invention of agriculture, tens of thousands of years ago.

For decades, social scientists have puzzled over the origins of cooperative and altruistic behavior that benefits the group at the expense of the individual. That seems to run counter to a basic "tooth and claw" view of evolution, in which each individual fights for survival, or at least the survival of its gene pool. One of the leading hypotheses is that a system to reward cooperation and punish non-cooperators ("free riders") grew out of a sense of genetic kinship between related individuals. But how far back did such a system arise?

To investigate that question, researchers spent two months interviewing more than 200 adult members of the Hadza group who still live in a traditional, nomadic, pre-agricultural setting. To chart the social connections, the researchers asked the adults to identify the individuals they'd like to live with in their next encampment. They also looked into gift-giving connections by giving their experimental subjects three straws of honey — one of the Hadza's best-loved treats — and asking them to assign them secretly to anyone else in the camp. That exercise produced a complex web of 1,263 "campmate ties" and 426 "gift ties."

Separately, the researchers gave the Hadza additional honey straws that they could either keep for themselves or donate for group distribution. That was used as a measure of cooperation vs. non-cooperation.

When the researchers analyzed all the linkages, they found that cooperators tended to group themselves together into one set of social clusters, while non-cooperators were in separate clusters. Even when other factors were taken into account, such as connections between kin and geographical proximity, the cooperation vs. non-cooperation distinction was significant. That finding suggested that even in pre-agricultural societies, social networking strengthened the connections between people inclined toward different kinds of behavior.

"If you can get cooperators to cluster together in social space, cooperation can evolve," said Coren Apicella, a postdoctoral researcher specializing in health-care policy at Harvard Medical School and the Nature paper's first author. "Social networks allow this to happen."

The researchers said the dynamics of the Hadza social networks — including the kinds of ties that bind a group's most popular members and the reciprocal connections within the group — were indistinguishable from previously gathered data about social networks in modern communities.

"We turned the data over lots of different ways," Fowler said in the news release. "We looked at over a dozen measures that social network analysts use to compare networks, and pretty much, the Hadza are like us."

Beyond the Facebook angle, the rise of relationships between cooperative individuals has larger implications for the study of human evolution. "This suggests that social networks may have co-evolved with the widespread cooperation in humans that we observe today," the researchers wrote.

Update for 2:15 p.m. ET: In a Nature commentary, University of British Columbia anthropologist Joseph Henrich said that the study provided a "glimpse into the social dynamics of one of the few remaining populations of nomadic hunter-gatherers" — and pointed up the parallels between modern-day social networking and the kind of society in which our distant ancestors lived.

One of the more interesting findings was that non-cooperators preferred to associate with other non-cooperators, rather than with the givers in the Hadza group, Henrich told me. That could be because people tend to make those they associate with more similar to themselves — sort of like a curmudgeonly married couple. Or it could be because non-cooperative types avoid the cooperators in the first place — sort of like the high-school kids who shun the goody-goodies and form their own clique of bad boys and girls.

Henrich said the cooperation vs. non-cooperation distinction was surprisingly strong. "In fact, the gift-network results indicate that this extends to friends of friends: if your friend's friend is highly cooperative, you are likely to cooperate more, too."

He said the findings support the principle of homophily in social relations: "People tend to pick people like themselves." But does the cooperation connection apply to modern-day social networks as well? If you're a giving person, do you tend to friend other givers online? "We don't know," Henrich told me. That's a topic for further research.

Update for 10:35 p.m. ET: In a follow-up phone interview, Fowler told me the results that he and his colleagues are reporting add a new twist to the old nature vs. nurture debate. People aren't shaped merely by genetics and their physical environment, he said.

"Social networks were actually just as important as the other two," he said. There may even be a genetic component to the associations you make. Along with Christakis and UCSD's Christopher Dawes, Fowler conducted research suggesting that genetic factors affect social behaviors. Previous studies have also shown that social networking among hunter-gatherer societies like the Hadza are not governed strictly by kin-based relationships.

"What's new here is that we've specifically tied this idea of cooperation to ties between non-kin," Fowler said.

Fowler acknowledged that studying hunter-gatherer societies are not a foolproof way to trace the evolutionary roots of the behaviors we see in modern-day society, including Facebook friending and Twitter tweeting. "This isn't necessarily the be-all and end-all of determining what we were like hundreds of thousands of years ago," he said. But considering that scientists can't interview Stone Age social networkers, Fowler believes this is one of the best methods available to anthropologists.

More social-network science:

• Human brain limits Twitter friends
• As social network grows, so does the brain
• Study suggests blogging makes new moms happy
• Key to social-network success: Get a media star to join

In addition to Apicella, Christakis and Fowler, authors of "Social Networks and Cooperation in Hunter-Gatherers" include Cambridge University's Frank Marlowe.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

USDA

When humans first started to farm, we became shorter and less healthy. The effect didn't last forever, especially in the developed world following the industrialization of food systems, the researchers say. Shown here are wheat fields in eastern Washington.

People got shorter and sicker everywhere in the world when they started to farm, according to a recent study that suggests the transition to an agricultural lifestyle came at a biological cost.

The transition occurred at different times in different places around the world beginning about 10,000 years ago in the Fertile Crescent, an arc of land spanning modern day Egypt to the border between Iraq and Iran.

As people gave up the diverse diet of foraged foods and settled on eating a few staple food crops they "experienced nutritional deficiencies and had a harder time adapting to stress," Amanda Mummert, an anthropology graduate student at Emory University, said in a news release.

Compounding the problem, growth in population density spurred by agricultural settlements led to an increase in unsanitary conditions ripe for spreading infectious diseases and the transmission of novel viruses from livestock to humans, she added.

Eventually, this trend reversed itself and average heights for most populations began to increase. This is most evident in the 75 years or so since the industrialization of agriculture in the developed world.

The finding is based on a review of skeletal data on populations from various corners of the world, including China, Southeast Asia, and North and South America. Mummert and colleagues looked at skeletal height as well as dental cavities, bone density, and other indicators of health.

"Culturally, we’re agricultural chauvinists. We tend to think that producing food is always beneficial, but the picture is much more complex than that," Emory anthropologist George Armelagos, co-author of the review, said in the statement.

The findings support a theory he proposed in the 1984 book, "Paleopathology at the Origins of Agriculture," which showed a decline in health and rising nutritional diseases as humans shifted from foraging to agriculture. 

So, if the transition to agriculture was bad for our health, why did we do it? 

The geneticist Spencer Wells argues in his 2010 book, "Pandora's Seed: The Unforeseen Cost of Civilization,"  that the transition was driven by a cold snap between 12,700 and 11,500 years ago called the Younger Dryas. 

In the Near East, the cold spell was also a dry spell, which was bad news for hunter-gatherers there who had settled some of the world's first villages and subsisted on easily foraged fields of wheat and barley. 

The arid climate meant the grains clung to moist niches in the hills, not the valleys where the hunter-gatherers settled. The commute to the hills to forage grains was unsustainable. So someone — most likely a woman since they did most of the gathering — Wells argues, had the brilliant idea to plant grains closer to home. 

"Her first efforts must have been rewarded with admiration from the entire village," he writes. "Virtually overnight, humans had gone from being controlled by their food supply to controlling it." 

More on agriculture, health, and evolution:

• Humans still evolving as our brains shrink 
• Cow milk closely mimics that of human breast 
• Prehistoric feasting hall found 
• How climate change kills society