Researchers have found a genetic mutation in two people who need far less sleep than average, a discovery that might open the door to understanding human sleep patterns and lead to treatments for insomnia and other sleep disorders.

The finding, published in the Friday issue of the journal Science, marks the first time scientists have identified a genetic mutation that relates to sleep duration in any animal or human.

Although the mutation has been identified in only two people, the power of the research stems from the fact that the shortened sleep effect was replicated in mouse and fruit-fly studies. As a result, the research now gives scientists a clearer sense of where to look for genetic traits linked to sleep patterns.

“I think it’s really a landmark study,” said Dr. Charles A. Czeisler, a leading sleep researcher and chief of sleep medicine at Brigham and Women’s Hospital in Boston. “It opens up a window to the understanding of the genetic basis of individual differences in sleep duration. Now you have a piece of the puzzle and you can begin to try to trace back as opposed to having little information as to where to start.”