Health & Science

Native Americans’ roots are in Siberia

Native Americans, anthropologists agree, originally migrated to the Americas from Asia. But for decades scientists have debated when and how, with some contending that human beings came to the new continent in several waves—some arriving by boat from Polynesia 30,000 years ago, and others walking across a now-vanished land bridge from Siberia to Alaska. New DNA evidence has settled the issue: All the native peoples on the North and South American continents have the same genetic mutation, indicating that they are descendants of a single group of Asians that crossed the land bridge 12,000 years ago. University of Michigan researchers came to this conclusion after finding that the mutation occurs only in Asians who live in Siberia and in 29 native groups in Canada, the U.S., Central America, and South America. This genetic marker cannot be found in any other part of the world. Through further DNA analysis, the researchers found that the native Americans and Siberians diverged 12,000 years ago. Researcher Noah Rosenberg tells Discovery News that it’s possible, and even likely, that once the ancient nomads walked across what is now the Bering Strait, some of them used boats to travel south along the coastline, speeding their arrival in Central and South America.

Rams: the first bioweapons?

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People may have used biological weapons more than 3,000 years ago, a new reading of ancient texts suggests. In 1335 B.C., an epidemic of tularemia—the “rabbit fever” that causes skin ulcers, respiratory failure, and death—was passed from animals to humans, spreading among the Hittite empire in modern-day Turkey and Syria. About 15 years later, the Hittites began warring for territory with another ancient people, the Arzawans. When they began fighting the Hittites, the Arzawans were healthy, but as the war proceeded, they began to fall sick. At the same time, ancient texts indicate, rams began to mysteriously appear on the outskirts of their communities, and were taken back to their herds of domesticated sheep. “They started wondering, ‘Why do these rams start showing up on the road?’” microbiologist Siro Trevisanato tells New Scientist. Two years later, so many of the Arzawans were sick with tularemia that they had to give up on their claim for the contested land. Trevisanato believes that the rams were “biological warfare agents” meant to weaken an enemy tribe. The Hittites, he says, “must have had the bright idea” to infect rams with tularemia, and to use them as vectors with which to introduce the epidemic among the Arzawans.

You can’t make up your sleep debt

Millions of Americans skimp on sleep on weekdays so that they can put in extra hours at work or school, and then try to catch up on the weekends. A new study says that strategy doesn’t work, and can hurt your concentration, memory, and ability to think clearly. In tests of sleep-deprived rats and sleep-deprived humans, researchers found that those who were allowed to catch up on lost sleep still performed worse on tests than subjects who always got enough sleep. After just one night of little or no sleep, study author Fred Turek tells USA Today, people are able to recover by increasing the time spent in deep sleep cycles the next night. But after a few nights’ sleep loss, Turek says, “The ability to compensate for lost sleep is itself lost, which is damaging mentally and physically.” Studies have not determined how long the fuzzy thinking, slower reaction times, and poor memory lasts, but sleep experts warned that if lost sleep is a chronic problem, the effects might be permanent. “The deficits can become severe,’’ said sleep expert David Dinges of the University of Pennsylvania School of Medicine. “You need to make sure sleep time is protected.’’

The new, lower fever

Everyone knows that the normal body temperature is 98.6 degrees Fahrenheit. Everyone, says the Los Angeles Times, is wrong. For most adults, the natural body temperature is actually half a degree cooler—98.1 degrees. How did the wrong temperature get established as the standard? Back in the mid-19th century, German doctor Carl Reinhold August Wunderlich recorded the body temperatures of 25,000 people with his mercury thermometer, which at the time was still a newfangled instrument. Through painstaking measurements and tedious math (he had to average about a million readings by hand), Wunderlich came up with the now-familiar average of 98.6 degrees. But more recent studies found that body temperature is flexible—slightly higher in women than in men, lower in whites than in blacks, higher in children than in adults, and lower in senior citizens—but generally lower than 98.6. This left scientists puzzled as to how Wunderlich came up with that number. When they examined his only thermometer, they found it to be calibrated wrongly. All of his readings were false.