Health & Science

The mid-life crisis is real; Watch out for double dippers; Building artificial DNA; AIDS patients who aren’t infectious; Have humans created a new era?

The mid-life crisis is real

Contrary to conventional wisdom, it’s not the teenage years or old age that are most likely to leave people depressed and dissatisfied. It’s middle age. After 30 years of collecting data from 2 million people across the globe, a team of international researchers has found that most people feel a significant dip in happiness and life satisfaction somewhere between 40 and 50, with some people lapsing into full-blown depression. The malaise that hits during these years was found in all kinds of populations from Azerbaijan to Zimbabwe, whether people were poor, rich, childless or not, married, divorced, or single. But 40-somethings can take heart. The midlife slump is temporary, and lifts by the mid-50s. In fact, the survey found that life satisfaction, if charted on a graph, has a “U’’ shape, with people very satisfied with their lives in their 20s and again late in life. “By the time you are 70, if you are physically fit, then on average you are as happy and mentally healthy as a 20-year-old,’’ study author Andrew Oswald tells Scientific American. “Realizing that such feelings are completely normal in midlife might even help individuals survive this phase.”

Watch out for double dippers

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If you see someone dipping a half-eaten chip into the guacamole at your next party, beware: “Double-dipping’’ can spread cold and flu viruses and other germs. Inspired by an episode of Seinfeld in which the character George Costanza is caught double-dipping, professor Paul Dawson enlisted undergraduate students to dip a chip they’d already bitten into bowls of chocolate syrup, cheese dip, and salsa. He found that after three to six re-dips, the students had transferred 10,000 aerobic bacteria from their mouths to the dip bowl. Of the three dips, salsa wound up with the most bacteria because its runny consistency allowed it to drip from a dipped chip back into the bowl. “Before you have some dip at a party,” Dawson tells The New York Times, “look around and ask yourself, Would I be willing to kiss everyone here?”

Building artificial DNA

Scientists have taken a giant step toward creating life out of chemicals, constructing the DNA of a bacterium in the laboratory. After decoding the gene sequence of one of the world’s simplest bacteria, a venereal parasite called Mycoplasma genitalium, genetic pioneer J. Craig Venter and his team were able to create a similar gene sequence from scratch. The loop of custom-built DNA—which has 582,970 base pairs—contains all the instructions the bacteria need to live and reproduce. “The entire process began with four bottles of chemicals,’’ Venter tells the Los Angeles Times. He hopes to soon insert the artificial DNA into a cell, where it would presumably “boot up’’ and begin directing the cell’s activities. If scientists perfect the technique, they could design and create one-cell organisms that could produce medicines, fuels, or industrial chemicals as part of their life cycle. “There are barriers,” Venter says. “But we are confident that they can be overcome.”

AIDS patients who aren’t infectious

AIDS patients who have been treated effectively with the latest cocktail of antiretroviral drugs no longer infect other people through sex, a new study has found. The drugs are so potent at suppressing HIV that patients—while not “cured’’—are left with a small amount of the virus circulating in their bodies. That, say Swiss researchers, prevents the HIV-positive person from transferring his or her virus to a partner through vaginal intercourse. (Anal intercourse was not studied.) The researchers concluded that it is safe for heterosexual patients who’ve taken the drug cocktail for at least six months to have unprotected sex with HIV-negative partners. Many groups of activists and doctors object to that advice, saying it may mislead HIV-positive patients into resuming risky behaviors without informing their partners. If a patient failed to follow the prescribed treatment regime, or decided to have unprotected anal sex, the critics say, there would be a significant risk of infecting his or her partner.

Have humans created a new era?

The impact of human activity on the globe has been so profound that some scientists say we’ve entered a new geological epoch. The current epoch, the Holocene (“entirely recent”), encompasses the last 11,500 years. It’s defined as the time period since the end of the last ice age, and is preceded by the Pleistocene epoch, when enormous mammals such as sabre-toothed cats and mammoths roamed the earth. But since the population of humans hit 1 billion about 200 years ago, a group of geologists argues, the landscape of our planet has been profoundly transformed. Industry, the burning of fossil fuels, and other human activities have vastly increased both the amount of carbon dioxide in our air and the amount of lead, mercury, and other toxins in our water and soil; filled rivers and lakes with sediment; and dramatically altered populations of animals, insects, and fish. So the Geological Society of London is proposing that we christen modern times the “Anthropocene” epoch. The argument for an Anthropocene epoch makes perfect sense, American geologist Richard Alley tells Science. “In land, water, air, ice, and ecosystems, the human impact is clear, large, and growing,’’ he says. “A geologist from the far distant future almost surely would draw a new line, and begin using a new name, where and when our impacts show up.’’

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