The question of why we sleep has been a longstanding subject of debate, with some theories suggesting that slumber provides respite for the brain, which allows it to filter out insignificant neural connections, build new ones, strengthen memories and even repair itself. However, new research has used mathematical approaches to tackle the adaptive significance of sleep, and the findings suggest that sleep has another purpose -- boosting our 'fitness' and future family line reproductive success.

Source: Better sleep linked with family tree strength