No one is making arguments for optimality of society! If your argument is that societies which traded off mental health of their members (almost certainly an in

No one is making arguments for optimality of society! If your argument is that societies which traded off mental health of their members (almost certainly an individual fitness hit) for other benefits that allowed them to outcompete individuals in other societies to overcompensate that fitness hit (similar to farmers beating hunter gatherers), I'd be curious to hear what these psychologically more idyllic less successful societies far less prone to PTSD would have looked like. You might be correct (and one sibling commenter has for example already blamed a change in the availability of social support networks), but it's certainly not obvious to me what the difference might be that suddenly made PTSD a recent "discovery". So I still think it's everything but "obvious in retrospect" in at least one meaning of that phrase. Maybe it was always with us, and people just failed to recognize it, but naively it would seem that live almost everywhere ought to have been massively more trauma inducing than in the contemporary West.