 18 minutes out of 22 days when everyone's asleep at the same time is a pretty incredible statistic, but it fits in perfectly with the idea of always having a sentinel on guard to alert the whole group to danger. So you can see how it works for a group, but what about the individuals? Wouldn't the early risers still have an advantage when it comes to gathering food for the day? Whatever they catch when they go out, whether it's hunting or whether it's gathering,