Yahoo launches Smallworld, a “Six Degrees” test, aiming to see how connected Facebook friends are. (ISTOCKPHOTO/Photo illustration)
In a ‘Six Degrees’ test, Yahoo aims to see how connected Facebook friends are

Are you only six people removed from Kevin Bacon or anyone else on the planet? Engineers at Yahoo are running an experiment on Facebook called Smallworld to see how closely connected people really are.

In the 1960s, psychologist Stanley Milgram conducted tests that used mail to connect strangers with one another. His findings led to the idea that people were removed by only “six degrees of separation,” but critics raised doubts about the results.

The idea remains intriguing and has since gained a firm footing in popular culture with the “Six Degrees of Kevin Bacon” trivia game. The rise of online social networking offers a unique opportunity to test the idea on a grand scale. Indeed, Facebook already hosts an application called “Six Degrees,” which is said to have more than 5.8 million members.

Now Yahoo wants to put the theory to what it calls “a proper scientific test.” People who sign up can try sending a message to a preselected target person somewhere in the world. You pick a Facebook friend you think is most likely to know how to reach that person and ask that friend to send a message to one of his or her other friends, and so on until the message gets to the target.

Drawing on Facebook’s 750 million users provides a huge pool. But there are obvious limitations. Many Facebook users make connections with almost anyone who asks. Do those “friends” represent meaningful social connections? What about the people you know in real life whom you never get around to friending? And, of course, the vast majority of people on the planet don’t have a Facebook profile. So will the result be a true representation of humanity’s interconnectedness?

In any event, the results could at least be entertaining. Are you a only a few degrees removed from Apple’s Steve Jobs, World Wide Web inventor Tim Berners-Lee or Facebook’s Mark Zuckerberg? Are we more connected now as a planet than we were in the 1960s? And if so, do those connections matter?

— Jeff Hecht, New Scientist

Study blames bug in human excrement for decline in Caribbean’s elkhorn coral

Coral reef ecologists have laid a persistent and troubling puzzle to rest. The elkhorn coral, named for its resemblance to elk antlers and known for providing valuable marine habitat, was once the Caribbean’s most abundant reef builder. But the “redwood of the coral forest” has declined by 90 percent over the past decade, due in part to highly contagious white pox disease, which causes large lesions that bare the coral’s white skeleton and kill its tissue.

Now, researchers say they have found the reason for this decline: human excrement. The finding represents the first example of human-to-invertebrate disease transmission and suggests a practical approach for halting the disease’s spread.

Coral reef ecologists Kathryn Sutherland and James Porter nine years ago linked white pox to Serratia marcescens, a bacterium found in the intestines of humans and a handful of other animals. But although the researchers suspected that human waste — stemming from septic tanks that leak sewage into the Florida Keys’ porous bedrock — was the culprit, they had no proof that the disease didn’t start with Key deer, cats, seagulls or any of the Caribbean’s other wildlife that also harbor the bacterium.

The researchers spent years collecting Serratia samples from healthy and diseased corals, from humans via a wastewater treatment facility in Key West, Fla., and from other animals.

Working through genetic fingerprinting, the team found only two that matched each other exactly: the Serratia strain found in white-pox-afflicted coral and the one drawn from human waste. To dispel any remaining doubt, the researchers cultivated small fragments of healthy, Serratia-free coral in the lab, and then exposed these to the human-specific strain. Within as little as four days, the healthy coral showed signs of white pox infection, they reported last week in PLoS ONE.

Sutherland and Porter hope their new evidence will encourage communities in the Caribbean to upgrade waste management facilities, replacing septic tanks with wastewater treatment plants. Key West has not seen a new case of white pox since its transition to an advanced wastewater treatment facility in 2001, the researchers say.

— Gisela Telis, ScienceNOW,

the daily online news service of the journal Science