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See Inside March 2009

In Brief

Roughly 12,900 years ago a global-cooling anomaly contributed to the extinction of 35 mammal species, including the mammoth. In some areas, average temperatures may have dropped as much as 15 degrees Celsius (27 degrees Fahrenheit). New evidence, in the form of diamonds several nanometers wide, supports a theory proposed last year that a comet collision or a similar explosive event threw up debris and caused the cooling.

Nanodiamonds occur only in sediment exposed to high temperatures and pressures, such as that produced by a cometary impact. Researchers uncovered them in six sites in North America: Murray Springs, Ariz.; Bull Creek, Okla.; Gainey, Mich.; Topper, S.C.; Lake Hind, Manitoba; and Chobot, Alberta. Preliminary searches in Europe, Asia and South America have also turned up similar finds in sediments of the same age, showing that the event had global reach. But it was definitely not as large as the one that wiped out the dinosaurs 65 million years ago. The study landed in the January 2 Science. David Biello

Interplanetary travel probably means that astronauts will need to carry ecosystems along to supply food and oxygen. Past studies of potential space food have considered poultry, fish and even snails, newts and sea urchin larvae, but they all have downsides. Chickens, for instance, require a lot of food and space, and aquatic life is sensitive to water conditions that may be hard to maintain.

Scientists at Beihang University in Beijing suggest recruiting silkworms, which are already eaten in parts of China. These insects breed quickly, require little space, food or water, and produce only minute amounts of excrement, which could serve as fertilizer for onboard plants. Silkworm pupae, which are mostly edible protein, contain twice as much essential amino acids as pork and four times as much as eggs and milk. The scientists, whose conclusions were published online December 24, 2008, by Advances in Space Research, also point out that chemical processes could even make the silk digestible. Move over, Tang. Charles Q. Choi

The robberies were a fitting end to a terrible year. On the Monday after Christmas, thieves in New York City held up five different banks in just over six hours, the near-final entries in the city's 444 bank robbery cases in 2008 a 54 percent increase over 2007. "It makes me think that the recession is making people go to extreme measures," one bystander told the New York Times, summing up the commonly held viewpoint that as the economy contracts, crime will swell to fill the void. And what a contraction we face: "People fear that we're headed for Armageddon," remarks David Kennedy, director of the Crime Prevention Center at the John Jay College of Criminal Justice.

But Kennedy and other researchers think that unemployment and financial desperation are not so inexorably linked to theft and murder. The factors that influence crime rates are far more varied and complex than any economic indicator.

Take, for example, the Great Depression. In the years after the stock market crash of 1929, crime plummeted as well. "People sitting in their houses don't make great targets for crime," says Bruce Weinberg, an economist at Ohio State University. "People going out spending cash and hanging out in big crowds do." That was especially true in the Roaring Twenties, a time that also suffered from Prohibition and its attendant crime syndicates.

American cities have gone through two other major crime epidemics in the last century one in the late 1960s into the early 1970s and another at the tail end of the 1980s into the early 1990s, when the nationwide murder rate hit an all-time high. The first happened at a boom time; the second struck during a recession. But in both cases, the primary underlying cause was a spike in the drug trade heroin in the 1970s, crack cocaine in the 1990s.

Even though these "outside shocks to the system," as Kennedy calls them, play a strong role in determining crime rates, recent research has teased out some links between the overall economy and crime. When Weinberg and his collaborators Eric D. Gould of Hebrew University and David Mustard of the University of Georgia examined young males with no more than a high school education the demographic group that commits the most crime they found that average wages and unemployment rates were directly linked to the incidence of property crimes. (Here property crimes refer to felonies such as burglary, auto theft and robbery, the last of which is ordinarily classified as a violent crime because of the implied use or threat of force.) Hard times also lead to more domestic abuse.

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