I'd like to see some concrete evidence that people in the past did in fact had "far less mental illness", and it is not just a result of them not being diagnosed. Most of the mental illnesses we know have been defined within last 100 years. In the past they may as well have been known as anything from demonic possession, and magic, to being stupid, being a brawler or a person ill-disposed.
Secondly, I wouldn't underestimate the amount of coercion that was going on in the past. Sustenance farmers probably didn't feel much direct coercion (besides the days when the nobility showed up to collect their dues), they were just mostly scared of going hungry. But factory workers in the early Industrial Revolution? Miners before, during and after that? Militaries of various times? If coercion causes mental illness, it should be reflected in the historical records. It's probably worth checking.
> I wouldn't underestimate the amount of coercion that was going on in the past.
Don't forget about the Inquisition. Most people hear that and think of the burning of witches and heretics, but that institution alone had a much wider array of non lethal punishments for all sort of behaviors considered "undesirable".
I have been in the Inquisition museum at the city of Guanajuato during the holidays, and they had a remarcable number of painful or even midly unconfortable artifacts that got used on people doing the pre-modern equivalent of littering. Victims would not face lasting harm, but the judicious infliction of pain plus public humiliation [1] was enough to keep them toeing the line more often than not.
[1] A remarkable example was a sort of iron flute. It was heavy and it had manacles for both hands and neck so that the transgressor would be forced in position as if playing it. They would attach it to the victims and send them back home for a few days to reflect on their sins, which was alteration of public order, or "wild partying".
It would be good to remember that he is largely drawing from hunter gatherer societies and not just "in the past" as you describe his thesis.
While valuable to look at, these agrarian and proto industrial societies also had large amounts of coercion.
As I read the other posts I see too many people wanting to T/F this thesis whereas I think it real value is as a critical tool to examine societies and the minds that have to learn to live in them.
Secondly, I wouldn't underestimate the amount of coercion that was going on in the past. Sustenance farmers probably didn't feel much direct coercion (besides the days when the nobility showed up to collect their dues), they were just mostly scared of going hungry. But factory workers in the early Industrial Revolution? Miners before, during and after that? Militaries of various times? If coercion causes mental illness, it should be reflected in the historical records. It's probably worth checking.