But according to a new study, some people have a genetic mutation that makes them feel perfectly alive after sleeping only half as much. While the human body typically takes about 8 or 9 hours to do this, having what’s called the “short sleep” mutation makes this possible within just 3 to 6 hours. The new mutation affects the gene SIK3, which is involved in regulating metabolism, energy, and circadian rhythm. When Fu genetically modified mice (which usually need about 12 hours of sleep) to have the SIK3 mutation, she found that they needed half an hour less of sleep to function. “These findings advance our understanding of the genetic underpinnings of sleep,” Fu and her team said in the study.