Sunday, July 06, 2014

Health and Science News

How fighting changed our faces

Men may have evolved to take a punch in the face. That’s the conclusion of a radical new theory suggesting that our male ancestors developed more robust brows, jaws, cheeks, and molars for protection during fights over mates, food, and other resources. The conclusions are based on an examination of the facial structures of Australopithecus—the immediate predecessors of the human genus Homo—compared with those of apes and modern humans. “It turns out that the parts of the face that became stronger were the parts of the face that most frequently break when modern humans fight,” evolutionary biologist David Carrier tells LiveScience.com. The theory builds on earlier work suggesting that the modern hand—with its flexible thumb, squared palm, and shorter digits—was adapted for aggression. Researchers note that the ability to form a fist entered the fossil record about 4 million years ago, around the same time that males developed their thicker facial features.

Why there’s a ‘man in the moon’

Astronomers have long debated why the moon’s maria, the dark areas that most recognizably form the “man in the moon,” are found only on the side nearest to Earth. New research now suggests that the answer is rooted in the satellite’s origins. The moon is widely believed to have formed some 4.5 billion years ago from debris thrown off by a violent collision between Earth and a Mars-size object. At that time, the moon was much closer to Earth than it is now, and the gravitational exchange between the two bodies kept one side of the moon always facing Earth. As a result, the near side was scorched by the 4,500-degree heat of Earth, keeping the surface molten even as the far side cooled. Meanwhile, the elements that had been vaporized in the collision condensed more rapidly on the cooler dark side. “When rock vapor starts to cool, the very first elements that snow out are aluminum and calcium,” astrophysicist Steinn Sigurdsson tells ScienceDaily.com. These elements formed a thicker crust that was more resilient to meteorite impacts. The near side’s weaker crust could be penetrated by the meteorites, releasing magma that pooled into large flat seas, which upon cooling, became the maria.

Rats think twice

Regret, or the ability to recognize that different choices would have resulted in better outcomes, was once thought to be a uniquely human emotion. But a new study indicates that rats may experience it as well, says Wired .com. Researchers set up a circuit of four “restaurants” offering various flavors of food and trained the rats to recognize that different audio tones indicated different wait times. Hearing a specific tone outside a restaurant, the rats could choose to stay or move on. In one hour on the circuit, the rats demonstrated individual preferences, waiting for some foods and not others. But more revealing was the way they reacted when they chose poorly: They stopped, looked backward, often ate quickly, and rushed to the next station, and were more likely to wait longer once they got there. In contrast, rats that chose wisely tended to rest and groom themselves between meals. The rats that made bad choices also experienced neural activity in the orbitofrontal cortex, the same part of the brain where humans register regret. “We know their brains are doing the same calculation,” says University of Minnesota neuroscience professor David Redish, measuring “the what-might-have-been that humans do when we feel regret.”

Pregnant women need more fish

Many expectant mothers aren’t eating enough fish. After years spent recommending limits on seafood consumption for pregnant women and young children, the Food and Drug Administration is now reversing course, saying that the benefits of the minerals and omega-3 fatty acids found in fish outweigh the risks of potential mercury contamination. “Emerging science now tells us that limiting or avoiding fish during pregnancy and in early childhood can mean missing out on important nutrients,” FDA chief scientist Stephen Ostroff tells NPR .org. Those nutrients “can have a positive impact on growth and development.” Mercury is known to impair neurological development in infants and young children, and while the FDA has so far resisted calls from consumer groups to label fish, the new guidelines do suggest avoiding predator species like shark, swordfish, and mackerel, which are more likely to contain mercury. However, two to three servings per week of low-mercury fish such as salmon, tilapia, and cod are now recommended.

The Trade That Made Us Human

The human brain consumes 20 percent of our energy each day, and new research suggests that its voraciousness may be the result of an evolutionary trade-off: Our ancestors developed smarts at the expense of strength. The findings are based on a study of metabolism—the way that bodies convert food into energy—in humans, chimps, mice, and rhesus monkeys. Specifically, scientists looked at the metabolic profile for kidney, thigh muscle, and three brain regions in each species. They then calculated how rapidly these metabolisms changed relative to each other, starting from when the species diverged and began evolving on different tracks. It turned out that over 6 million years, the prefrontal cortex changed four times faster in humans than in chimps, and muscle changed eight times faster—with more brainpower developing at the expense of our muscular strength. Pound for pound, humans today are about half as strong as monkeys and chimps, biologist Roland Roberts tells NationalGeographic .com. But we’re significantly smarter. “Weak muscles may be the price we pay for the metabolic demands of our amazing cognitive powers,” Roberts says.
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