There was a study done on a tribe of wild monkeys where mutual grooming to remove ticks/fleas/lice happened. Some monkeys 'cheated' and didn't pay forwards the

There was a study done on a tribe of wild monkeys where mutual grooming to remove ticks/fleas/lice happened. Some monkeys 'cheated' and didn't pay forwards the grooming they received. The study concluded that as long as cheaters were less than 5% of the population then mutual grooming continued. when the number of cheats exceeded 5% the system broke down and no mutual grooming happened for some time. It seems that a society can bear a certain amount of cheating before the system breaks down, a 'tipping point' of sorts. As long as we keep the cheating below the tipping point, the game continues, which is after all the most important aspect, I think.