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Discovered: Singapore is home to the least positive people on Earth; megapiranhas could swallow a turtle; the human hand has evolved to punch things; bats fly above virus vulnerability.

Singaporeans aren't happy. If we had to bet we would've put our money on North Korea, but a recent Gallup poll insists that Singaporeans have the least positive emotions in the world. Based on calls and in-person interviews with 1,000 adults in 148 countries, Gallup researchers found that Singaporeans were the least likely to report positive emotions. They didn't think they were treated with respect, didn't report laughing or smiling, said they had trouble getting rest, and said they didn't get much enjoyment out of their day. Which country had the happiest citizens? Panama. In fact, the top of the list is populated almost entirely with Latin American countries. [Asian Scientist]

The human hand evolved to break stuff. Take a look at your hands. Why are they so knuckling and full of joints? Because your supposed to punch things with them. University of Utah researchers studied martial artists, concluding that the structure of their hands and effectiveness of their blows developed over thousands of years of brawling. "There may, however, be only one set of skeletal proportions that allows the hand to function both as a mechanism for precise manipulation and as a club for striking," the researchers write. "Ultimately, the evolutionary significance of the human hand may lie in its remarkable ability to serve two seemingly incompatible, but intrinsically human, functions." [BBC News]

Why bats soar above viral diseases. Bats carry many of the world's nastiest diseases—SARS, Ebola, Hendra—so why aren't the susceptible to the diseases these viruses cause in humans and other animals? Christopher Cowled and his colleagues from the CSIRO Australian Animal Health Laboratory have found that bats may have evolved to soar above these diseases, literally. "We found genetic changes that are right in the intersection that handles DNA damage and initiates the frontline antiviral immune response," says Cowled. "We believe that flight was the initial trigger that led to improvement in the [immune] systems." [New Scientist]

Megapiranhas had huge appetites. And you thought the toothsome creatures from Jurassic Park were scary? The ancient ancestor of modern-day piranhas—the Megapiranha paranensis—could snap turtle shells and bite through catfish armor plates for breakfast, according to new studies. These sea beasts were about 1.3 meters long and were as heavy as 484 kilograms. T. rexes had bites that were three times as intense as that of the Megapiranha, but that's not so impressive when you consider that they were 100 times bigger. [ScienceNow]

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