Thursday, 15 July 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge

Happiness and Sadness Spread Just Like Disease

Posted: 14 Jul 2010 02:17 PM PDT

There may be a literal truth underlying the common-sense intuition that happiness and sadness are contagious.

A new study on the spread of emotions through social networks shows that these feelings circulate in patterns analogous to what's seen from epidemiological models of disease.

Earlier studies raised the possibility, but had not mapped social networks against actual disease models.

"This is the first time this contagion has been measured in the way we think about traditional infectious disease," said biophysicist Alison Hill of Harvard University.

Data in the research, in the July 7 Proceedings of the Royal Society, comes from the Framingham Heart Study, a one-of-a-kind project which since 1948 has regularly collected social and medical information from thousands of people in Framingham, Massachusetts.

Earlier analyses found that a variety of habits and feelings, including obesity, loneliness, smoking and happiness appear to be contagious.

In the current study, Hill's team compared patterns of relationships and emotions measured in the study to those generated by a model designed to track SARS, foot-and-mouth disease and other traditional contagions. They discounted spontaneous or immediately shared emotion — friends or relatives undergoing a common experience — and focused on emotional changes that followed changes in others.

In the spread of happiness, the researchers found clusters of "infected" and "uninfected" people, a pattern considered a "hallmark of the infectious process," said Hill. "For happiness, clustering is what you expect from contagion rates. Whereas for sadness, the clusters were much larger than we'd expect. Something else is going on."

Happiness proved less social than sadness. Each happy friend increased an individual's chances of personal happiness by 11 percent, while just one sad friend was needed to double an individual's chance of becoming unhappy.

Patterns fit disease models in another way. "The more friends with flu that you have, the more likely you are to get it. But once you have the flu, how long it takes you to get better doesn't depend on your contacts. The same thing is true of happiness and sadness," said David Rand, an evolutionary dynamics researcher at Harvard. "It fits with the infectious disease framework."

The findings still aren't conclusive proof of contagion, but they provide parameters of transmission rates and network dynamics that will guide predictions tested against future Framingham results, said Hill and Rand. And whereas the Framingham study wasn't originally designed with emotional information in mind, future studies tailored to test network contagion should provide more sophisticated information.

Both Hill and Rand warned that the findings illustrate broad, possible dynamics, and are not intended to guide personal decisions, such as withdrawing from friends who are having a hard time.

"The better solution is to make your sad friends happy," said Rand.

Image: Morgan/Flickr.

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Citation: "Emotions as infectious diseases in a large social network: the SISa model." By Alison L. Hill, David G. Rand, Martin A. Nowak and Nicholas A. Christakis. Proceedings for the Royal Society B, Published online before print, July 7, 2010.

Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecological tipping points.

Poop Study: People Have Friendly Gut Viruses

Posted: 14 Jul 2010 11:42 AM PDT

It's not just the bugs in our guts that are surprisingly friendly. It's our viruses, too.

After slowly coming to appreciate the importance of symbiotic bacteria for running our bodies, scientists have wondered whether viruses also help. Now a gene-hunting expedition in the gut has found it teeming with highly personalized viral communities.

"Viral diversity and life cycles are poorly understood in the human gut and other body habitats," wrote researchers led by Washington University microbiologist Jeffrey Gordon in a study in the July 14 Nature. Unlike gut bacteria, these viruses — our "virome" — appear uniquely individual, differing even between identical twins.

The study is a natural extension of research on internal bacteria, which outnumber each body's human cells by a factor of 10. Collectively called the microbiome, they perform digestive and metabolic tasks our bodies can't accomplish unaided. In a way, the microbiome is as much a part of us as any organ. It just happens to come from another order of life.

Gordon's lab, which specializes in the links between gut bacteria and obesity, has been at the forefront of microbiome research. That's led them to question whether, just as scientists once failed to appreciated the importance of bacteria, they've overlooked viruses.

"The idea was that having a virus, under any circumstance, is basically bad. Sometimes it causes disease, sometimes not, but having viruses present is abnormal," said Andrew Gewirtz, an Emory University microbiologist not involved in the study. "As the complexity of the microbiota became appreciated, people have wondered whether that is really true, or if there's a normal population of viruses. This is the first paper to look in a systematic way."

Because intestinal tracts are difficult to study directly, Gordon's team sampled DNA from the stool samples of four identical-twin pairs and their mothers. They identified which sequences came from bacteria, and which from viruses.

Unlike stomach bacteria, which are relatively consistent between siblings, viral profiles varied markedly. The pattern's significance isn't yet evident, but it's striking.

Samples taken at later dates showed that viral communities were stable, rather than fluctuating as would be expected if competing with bacteria. Virome and microbiome coexist peacefully, and may even cooperate.

More than 4,000 different viral strains were ultimately identified, 80 percent of which hadn't been seen before. Despite the novelty, the researchers could match individual genes to known functions. This doesn't show the targets of those functions, but it's possible that "viral genes are just providing that little something that bacteria don't have," said Gewirtz.

Gordon's team next intends to see what happens when human virome samples are added to mice engineered to contain human microbiomes. Other scientists will further explore the virome's role.

"Human microbiome projects have been initiated throughout the world," wrote Gordon's team. "Our results indicate that these metagenomic studies should also include" the virome.

Images: Left: the human colon against a background of virus-like particles. Right: functional associations of genes from friendly stomach viruses and bacteria./Alejandro Reyes, Vamsi Narra, Laura Kyro, and Jeffrey Gordon.

See Also:

Citation: "Viruses in the faecal microbiota of monozygotic twins and their mother." Reyes A, Haynes M, Hanson N, Angly FE, Health AC, Rohwer F and Gordon JI. Nature, Vol. 466 No. 7304, July 15, 2010.

Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecological tipping points.

Apes, Old World Monkeys May Have Split Later Than Thought

Posted: 14 Jul 2010 11:30 AM PDT

A slope-faced, big-toothed creature from the distant past has inspired scientists to recalibrate the ancient evolutionary split between apes and Old World monkeys.

sciencenewsDiscoverers of a partial apelike skull in western Saudi Arabia say that it now appears that a poorly understood parting of major primate groups occurred between 29 million and 24 million years ago. A 2004 analysis of DNA from living apes and monkeys in Africa and Asia had estimated an earlier divergence, between 34.5 and 29.2 million years ago.

An intriguing mosaic of features on the newly unearthed fossil, which dates to between 29 million and 28 million years ago, suggests that it lived shortly before a common ancestor that gave rise to hominoids — a primate lineage that includes apes and humans — and the monkeys of Africa, Asia and Europe. A team led by anthropology graduate student Iyad Zalmout of the University of Michigan in Ann Arbor reports the find in the July 15 Nature.

Zalmout and his colleagues assign the skull to a new primate genus and species, Saadanius hijazensis.

"This is wonderful discovery, a real missing link that fills in a gap in our understanding of the timing and pattern of anatomical change involved in the evolution of Old World monkeys and apes," remarks anthropologist John Fleagle of Stony Brook University in New York.

Zalmout, working with members of the Saudi Geological Survey in Jeddah, found the partial Saadanius skull on Feb. 17, 2009, in a section of Saudi Arabia's Shumaysi Formation framed by previously dated volcanic ash layers. Based on the specimen's size and shape, the researchers estimate that Saadanius weighed 15 to 20 kilograms (33 to 44 pounds), making it a medium-sized primate for its time.

Saadanius sports a projecting snout, a relatively tall face with long, narrow nasal bones, broad cheek teeth and other traits resembling those of older primates previously unearthed at a geological formation on the edge of Egypt's Sahara Desert. Researchers estimate that those creatures lived between 35 million and 30 million years ago.

But a few critical anatomical features, including a long, tube-shaped ear canal, distinguish Saadanius from its primate predecessors, the scientists say. And unlike Old World monkeys and hominoids that evolved after about 24 million years ago, Saadanius — which Zalmout's group identifies as a male based on dental characteristics — lacked nasal sinuses and large canine teeth typical of later ape and monkey males.

For that reason, the researchers use 24 million years as the most recent estimate of when Old World monkeys diverged from apes.

Anthropologist Brenda Benefit of New Mexico State University in Las Cruces proposed in 1993 that a common ancestor of Old World monkeys and apes, or its close relative, would look much like the new fossil find. "Saadanius strikingly matches her prediction," says Michigan's William Sanders, a co-author of the new study.

Saadanius apparently lived not long before Old World monkeys and apes diverged from a common ancestor, Fleagle says. Unfortunately, a 5-million-to-10-million-year gap separates Saadanius from the earliest known Old World monkeys and hominoids, so key pieces of the evolutionary transition are still missing.

That makes it difficult to narrow down the timing of an ape–Old World monkey divergence, says anthropologist Elwyn Simons of Duke University in Durham, North Carolina. But the new fossil "fits in exactly as it should" in primate evolution, he holds.

Although additional fossil finds are needed, the Saudi specimen offers a more reliable age estimate for a crucial shift in primate evolution than can be gleaned from DNA studies of living apes and monkeys, comments anthropologist David Begun of the University of Toronto.

Image: Partial cranium of the discovered Saadanius specimen./Zalmout and Sanders.

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Our Eavesdropping-on-ET Strategy Not Likely to Work

Posted: 14 Jul 2010 09:01 AM PDT

Bad news for SETI: Even with the most sensitive radio telescopes yet designed, humans probably won't find intelligent aliens by listening in on their phones and televisions, a new study finds.

"Eavesdropping on ET is very hard, even with the latest radio telescopes," said astronomer Duncan Forgan of the University of Edinburgh, a coauthor of the study. "If we don't try any other ways of searching for aliens, then we may never find them."

Forgan and astronomer Robert Nichol of the Institute of Cosmology and Gravitation in the U.K. set out to test the suggestion that rather than building expensive telescopes dedicated exclusively to listening for signals from aliens, SETI — the search for extra-terrestrial intelligence — could be done on the cheap by piggy-backing on other astronomy missions.

Some astronomers hoped SETI searches could ride on the coattails of the planned Square Kilometer Array, which will probe the history of the universe with thousands of small antennas spread out either Australia or South Africa.

"We focused on the SKA because it will be an incredible advancement in radio astronomy," Forgan said. "It will be the most powerful radio telescope ever built."

The SKA will also be sensitive in the same frequency range that cellphones, radio and television operate in. If the aliens out there are anything like us, that frequency range is exactly where we should expect to find them, astronomers have suggested.

In 2007, astrophysicists Abraham Loeb and Matias Zaldarriaga of the Harvard-Smithsonian Center for Astrophysics calculated that signals similar to those used in human military radar could be detected from more than 160 light-years away using a telescope in the Netherlands called LOFAR, and more than 650 light-years away using the SKA.

But assuming these aliens have technology like ours, there won't be enough time to find them, Forgan and Nichol argue. Humans, the only intelligent civilization we know of, have been communicating using radio waves for only about 100 years — and we're beginning to go quiet. Advances in technology mean less power is needed to broadcast, and digital communication is starting to replace radio altogether.

Forgan and Nichol randomly generated about 500,000 alien civilizations based on current theories of planet formation, and an optimistic guess as to how many would develop life. They then assumed that each civilization broadcasts in radio for 100 years, and they can hear each other from up to 300 light-years away.

"All communication disappears," the team wrote. Even with a telescope like the SKA, the odds of eavesdropping on another civilization are one in 10 million. The results were posted in a paper on the astronomy preprint website and accepted for publication in the International Journal of Astrobiology.

A more fruitful strategy would be to target our searches, Forgan suggests. We may not be able to hear leaked signals, but we could still pick up a deliberate beacon from a civilization that wanted to announce its presence. A telescope dedicated to searching for such a beacon, like the Allen Telescope Array in northern California, would improve the odds to one in 10 thousand.

Jill Tarter of the SETI Institute thinks Forgan underestimates the usefulness of the SKA. "The SKA is being built with a large field of view and many simultaneous beams, so that there should in fact be significant observing time available for SETI," she said.

Whatever the odds, Loeb thinks we should eavesdrop, anyway. "Rather than speculate about how generic is our own evolution and whether others will be the same, we should just search," he said. He points out that a lot of technological advances are driven by social forces. For example, Earth gave off the most radio waves during the Cold War, when radar ballistic missile searches were common.

"Politics are impossible to predict, they don't follow laws of physics," he said. "We should just explore the sky, and try to set as strong limits as we can."

Forgan agrees. "We should always continue to eavesdrop as it is a cheap search method, especially if we piggy-back," he said. "If you don't listen, you won't hear anything."

Image: SKA

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