National Geographic : 2011 Dec
NOW PHOTO: WALTER ASTRADA, GETTY IMAGES A study using genetic molecules called microRNAs suggests turtles are CLOSER KIN to lizards than to crocodiles and birds. • To process low light levels at high latitudes, humans near the Earth's Poles have evolved BIGGER EYES AND BRAINS---though not greater intelligence---research says. • A DNA study finds several populations of the WORLD'S LARGEST SHEEP are genetically connected despite mountain- ous international borders. • A 36 FOOT LONG, HALF TON MUSHROOM has been found on a tree in China. ET CETERA Cholera Redux An ancient scourge keeps defying modern efforts to defeat it. Months after Haiti's earthquake, cholera appeared in the island nation for the first time in more than a century. Despite intensive containment attempts, the epidemic has now killed more than 6,000 people there. Recurrent outbreaks are plaguing sub-Saharan Africa and Southeast Asia as well. The bacterium, which causes severe diarrhea and can kill a person within hours, originated in the Ganges River Delta. In the 19th century Vibrio cholerae began to move around the world, spread by travelers. According to the World Health Organization, the current global pandemic started in . Infectious-disease experts suspect peace- keeping troops brought cholera to Haiti last year; DNA tests link it to strains in Southeast Asia. People get cholera from contaminated food or water. But new research shows many environmen- tal factors---including water temperature, flow, and pH---affect outbreaks. That makes them difficult to predict. And climate change may be having an impact. "We're now seeing protracted epidemics," says Peter Hotez of Houston's National School of Tropical Medicine. To contain them, new predictors and a live vaccine are needed. ---Nancy Shute In Port-au-Prince, Haiti, a man su ering from cholera lies in an improvised hospital.