Humans are not the only creatures with an internal biological clock. Fruit flies have two, which separately control morning and evening activity, scientists said on Wednesday. Separate teams of researchers in the United States and France discovered the dual clocks in brain cells of fruit flies in a finding that will provide insights into the workings of our own internal clock, which controls functions such as sleeping, waking and body temperature. "It was always intriguing that flies had two peaks of activity, in the morning and evening, with a siesta during the day and not very much activity at night," said Michael Rosbash, of Brandeis University in Massachusetts, who headed the American group. "There are several ways to explain that. One possibility was that there were two clocks running -- one governing the morning peak and one governing the evening peak," he added. Rosbash and Francois Rouyer and his colleagues at the National Center for Scientific Research (CNRS) in France pinpointed the two clocks, which communicate with each other, in the neurons in the brains of fruit flies. Their research is reported in the science journal Nature. The dual clocks are in clusters in different parts of the brain of the flies and produce different signaling molecules. "It's as if there is a wiring circuit from one set to the next and, under natural light conditions, one can regulate the physiology of another," Rosebush said. The scientists suspect that mammals, including humans, may also have dual internal clocks, but they have yet to be found.
