Read the text and determine if the sentence is true (see options at the end):

A good night's sleep becomes more elusive with age, but what older people label as insomnia may actually be an evolutionary survival trait that helped keep their ancestors alive. A study of modern hunter-gatherers in Africa found that when family members of all different ages live together, the differences in their sleeping patterns ensures that at least one person is awake, or sleeping very lightly, at all times. The research suggests that mismatched sleep schedules and restless nights may be an evolutionary leftover from a time thousands of years ago when a lion might be on the prowl at 2am.

Sentence: there is no research on mismatched sleep
Choose from: + Yes; + It's impossible to say; + No;
No