Health & Science

A shoe from the dawn of history

Archaeologists working in Armenia have unearthed what appears to be the world’s oldest shoe. The shoe, made from a single piece of cowhide and meticulously stitched with leather thread, is roughly 5,500 years old—about a thousand years older than the Great Pyramid of Giza. It was found in a large cave and was so well preserved under a protective layer of sheep dung that researchers first thought it was just a few centuries old; even the laces, threaded through leather eyelets, were intact. “These were probably quite expensive shoes, made of leather, very high-quality,” team member Gregory Areshian tells The New York Times. Previously the oldest known shoe belonged to Ötzi, the frozen tribesman found in the Alps, and dated back 5,100 years. The shoe’s small size suggests it may have been worn either by a woman or a man with a small foot, and it was filled with grass, either for warmth or comfort. Quite clearly, it had been worn. “You can see the imprints of the big toe,” said another team member, Ron Pinhasi.

How crocodiles ride the currents

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Saltwater crocodiles are notoriously weak swimmers, yet they’ve managed to colonize numerous far-flung Pacific islands. How did they travel so far? Now an Australian study offers a surprising answer, reports Scientific American: Crocodiles surf. The researchers tagged various adult crocs with transmitters and tracked them for a year as they moved around a tidal river and the open sea. On short trips, the crocs traveled both with and against the current, but on long trips of several hundred miles in the open sea, they always went with the flow. “Crocodiles ride the currents to cut the energy costs of traveling,” says lead scientist Craig Franklin. “They get a free ride.” Franklin says that the crocs seem to know when the current is flowing in the direction they want to go and time their travels accordingly. One animal, a 12-foot male, swam 15 miles a day in the sea for nearly a month, riding a seasonal offshore current. “Why he went there, we have absolutely no idea,” says ecologist and co-author Hamish Campbell, “but it seems very deliberate, purposeful movements.”

I’m fine—the heck with you

Don’t feel bad for today’s college students; they certainly don’t feel for you. A new University of Michigan study has found that empathy among today’s college students is about 40 percent lower than it was among their counterparts three decades ago. Researchers looked at standard personality test results for some 14,000 students going back 30 years. They found that, compared with students of the late 1970s, today’s young people are far less likely to agree with statements like, “I try to understand my friends better by imagining how things look from their perspective.” Researchers theorize that the rise of social media is one contributing factor, since it leads to having large groups of disposable “friends” with whom one has superficial relationships. “The ease of having friends online might make people more likely to just tune out when they don’t feel like responding to other people’s problems,” study co-author Edward O’Brien tells USA Today. Other possible factors: violent video games and reality TV shows that emphasize ruthless competition, and the hypercompetitive atmosphere now found in some high schools and colleges.

When kids have two mommies

One mom is good, but might two be better? A 25-year study has found that children raised by lesbian couples had higher self-esteem and more confidence than kids in straight families; they also performed better academically and were less likely to break rules or act aggressively. The results were “something I hadn’t anticipated,” psychiatrist and study author Nanette Gartrell tells Time. The study, which began in 1986, followed lesbian couples who’d conceived using in vitro fertilization; the researchers conducted psychological interviews every few years and ended up following 78 kids through at least their 18th birthday. That the pregnancies all had to be sought and planned may be a factor, researchers said, since involved, dedicated parents make better parents in general. At the very least, says Gartrell, the results demonstrate that children of lesbian parents certainly aren’t worse off than their counterparts, and in fact “are psychologically happy and high-functioning.”

Asleep, but having sex

Some people talk in their sleep, others walk. But a third, smaller group reports a more unusual problem, according to a Canadian study: They have sex while sleeping. Scientists at a sleep clinic in Toronto reviewed the cases of 800 patients who’d sought help there; they found that one in 12 had engaged in sexual activity while asleep, a phenomenon called sexsomnia. (Most have no memory of the experience and only learn about it later from their partner.) Because the study focused on a select group—people who’d been referred to a sleep clinic—the incidence of sexsomnia is likely much lower among the general population. “At night you’re supposed to be sleeping,” psychiatrist Sharon Chung tells The New York Times. “Anything that stops you from sleeping at night is bad—not because of the behavior, because it stops you from sleeping.”