Health & Science

Islands of abundance built on trash

The wasteful ways of prehistoric humans might be the reason why thousands of “tree islands” dot the wetlands of the Florida Everglades, providing nesting sites for alligators and other species. A new study suggests that these havens of biodiversity sit not on protrusions of the carbonate bedrock, as scientists previously thought, but rather atop piles of garbage discarded some 5,000 years ago by ancient Floridians. “This goes to show that human disturbance in the environment doesn’t always have a negative consequence,” study author Gail Chmura, a paleoecologist at McGill University in Montreal, tells LiveScience.com. The trash mounds, called middens, contain charcoal, shell tools, and pottery, and could have risen high enough out of the shallow water to allow vegetation to take root. The middens also contain bones, a source of the nutrient phosphorus, which is otherwise rare in the soil of the Everglades. Scientists disagree about whether the garbage dumps initiated or merely aided the islands’ growth, but they all worry that modern tree-clearing and artificial flooding will destroy these valuable habitats. “The trees are key,” Chmura says, to keeping the islands’ rich sediment in place.

The rains of Titan

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Earth is the only place in the universe known to have abundant water, but it’s not alone in having spring rains. Images from NASA’s Cassini probe have revealed compelling evidence of a rainy season on Titan, Saturn’s largest moon. The precipitation there, however, is of a particularly inclement sort: Titan’s temperatures are as low as -297 degrees Fahrenheit, and what rains down from its clouds is liquid methane, not H2O. Still, lead researcher Elizabeth Turtle tells ScienceDaily.com, “It’s amazing to be watching such familiar activity as rainstorms on a distant, icy satellite.” The sight has been a long time coming for Cassini’s minders, since it takes Saturn and its moons 29 Earth years to make a single trip around the sun. When Cassini began orbiting the planet in 2004, it was the equivalent of mid-January on Titan, and its equator looked like an arid desert. But as spring approached the moon’s northern hemisphere in 2010, a vast storm darkened its equatorial region with methane rain. Turtle says that as Saturn’s orbit shifts, Titan’s equatorial regions get more direct sunlight and the moon’s surface warms. As that heat rises, storms result, much as they do in the tropics on Earth. Tracking Titan’s seasonal weather patterns, Turtle says, could even help scientists understand “similar processes on our own planet.”

Self-control and aggression

Dieters beware: Choosing an apple over a chocolate bar could leave you itching for a fight. A new University of Texas study suggests that people have a finite ability to exercise self-restraint, and that when it’s exceeded, they’re resentful, angry, and prone to aggression. Researchers found that people who chose a healthy snack over a tastier one tended to prefer movies with revenge themes over milder flicks. Dieters were also more irritated by marketing messages that used phrases like “you ought to,” because they sounded controlling. And it’s not just virtuous food choices that sour a mood. People who showed financial restraint in their choices later showed a decided preference for pictures of angry faces over fearful ones. The results suggest that “people have a diminishable supply of energy that the body and mind use to engage in self-control,” researcher Kathleen Vohs tells USA Today. When people are asked to give up too much at one time, she says, it’s natural for them to rebel—and fail.

Why the long neck?

Plant-eating sauropods like Brachiosaurus had enormous bodies, tiny heads, and necks five times longer than any giraffe’s. Why would evolution favor such a strange design? Researchers in Liverpool and Glasgow figure that the 88-ton creatures behaved like the “clunky cylinder vacuum cleaners” of the 1950s: Their bodies stayed in one place while their hose-like necks allowed their heads to forage widely for ground vegetation. The dinosaur’s small jaws and teeth, they say, merely sucked up plant matter, leaving the animal’s gut the hard work of digesting barely masticated food. Under this strategy, Brachiosaurus’s 30-foot-long neck provided an evolutionary advantage: The researchers estimate it would have been 80 percent more efficient than a 20-foot-long neck. The British study also suggests Brachiosaurus could have used that extra energy to reach treetops like giraffes do. But Australian physiologist Roger Seymour tells Science it would have been impractical to pump blood that far upward to the brain for long periods. The new study presents a “valid mathematical argument” that Brachiosaurus foraged down low, he says, and the researchers should “just leave it there and not ask the sauropods to raise their necks.”