According to Chris Ryan (PhD and author of Sex at Dawn), hunter gatherers work around 20-25 hours per week, in line with the comments above of what they found w

According to Chris Ryan (PhD and author of Sex at Dawn), hunter gatherers work around 20-25 hours per week, in line with the comments above of what they found was near ideal for happiness, productivity, and concentration. There really isn't much hard science when it comes to things like human productivity standards, in the same way there's not too much hard science on ideal diet. Too many variables, highly individualized, and like all multi-objective optimization, highly context dependent.