> I've always wondered if we're going to one day find out that the 8 hours sleep thing was wrong and that it's physical exercise we truly need. Two comments on

> I've always wondered if we're going to one day find out that the 8 hours sleep thing was wrong and that it's physical exercise we truly need. Two comments on that: The 8 hours sleep is a population average. It is very unlikely that you will need 8 hours of sleep, very likely your body will need more or less, and this will change as you age. You might very well be a 6 hours type. That would basically invalidate what we know from animals - they are most vulnerable when they sleep, so it's unlikely evolution mad a mistake given all animals sleep, even the ones that don't have brains.