Health & Science

Are dogs the brainiest pets?

Which are smarter, cats or dogs? The latest scientific contribution to that perennial debate puts dogs on top, says USA Today. A team of evolutionary biologists at Oxford University analyzed the evolving brain size of some 500 mammalian species, living and fossilized, going back 60 million years. They found the greatest increases in animals that live in social groups; monkeys saw the biggest gains, followed by horses, dolphins, camels, and dogs. The brain size of more solitary animals, including cats and rhinos, increased less. Study co-author Robin Dunbar says social animals “needed to think more” in order to better manage complex interactions with peers. “Even animals that have contact with humans, like cats, have much smaller brains than dogs and horses because of their lack of sociality,” Dunbar says. That hardly proves that dogs are smarter than cats, veterinarian Pete Wedderburn tells the London Telegraph. Measured as a fraction of body weight, cats’ brains are actually larger than those of dogs, with almost twice as many neurons. Dogs may be better at tasks assigned by humans, he says, but “no self-respecting cat should be expected to carry out random human demands.”

How blood reveals age

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Traces of blood left at a crime scene can now be used to estimate a suspect’s age, through a test devised by Dutch biologists. Blood contains T cells, which are known to throw off circular molecules of DNA as they help defend the body against bacteria, viruses, and parasites. The researchers have found that as a person gets older, the rate at which these distinctive molecules are created slows steadily; by counting them in a blood sample, researchers can determine age within nine years either way. In cases where investigators have no evidence but bloodstains­­—and no suspects to compare them to—narrowing the field to individuals within a single generation can make a big difference. “This will never be a tool that ends up in front of a court,” study author Manfred Kayser tells Nature News. But it’s a key step toward using DNA evidence alone to describe a person’s appearance.

A way to prevent AIDS

A drug commonly used to treat people infected with the AIDS virus helps block the infection from taking hold in the first place, according to a study by the University of California at San Francisco. Researchers recruited 2,500 sexually active gay and bisexual men and gave half of them a placebo to take daily, while the other half were given the widely used AIDS drug Truvada. After a little more than a year, the researchers concluded that men who’d faithfully taken Truvada reduced their chance of infection by 73 percent. The results “represent a major advance in HIV-prevention research,” Kevin Fenton, a physician with the Centers for Disease Control and Prevention, tells Science News. But while the benefits of a prophylactic drug regimen are obvious, there are concerns that such drugs might backfire by encouraging people to engage in risky behavior. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, notes that while a vaccine “either works or it doesn’t work,” the effectiveness of a preventive drug treatment “really depends on the individual who’s taking it.”

A rare glimpse at antimatter

Scientists have finally managed—very briefly—to capture a minute quantity of antimatter, that mysterious stuff villains used to try to blow up the Vatican in Dan Brown’s novel Angels & Demons. Antimatter consists of particles with electric charges that are opposite to those of ordinary matter; antihydrogen, for instance, consists of a single positron (the opposite of a negatively charged electron) orbiting a single antiproton. Studying antimatter is notoriously difficult because when it encounters matter, the opposites annihilate each other in a flash of energy. Physicists at CERN, the European particle physics lab near Geneva, used high-powered magnets to create and hold 38 antihydrogen atoms for as long as a sixth of a second—far longer than ever before. It’s a step toward testing whether antimatter responds to forces the way Albert Einstein said it would in his special theory of relativity. “It’s so exciting because now we can subject antihydrogen to anything anyone has ever done with hydrogen in the past,” Jeffrey Hangst, a physicist at the University of Aarhus in Denmark and a project spokesman, tells Science News. “In 10 years people will forget Dan Brown, but we’ll be in the textbooks.”