Afaik the 25-30 lifespan is not quite right. People tended to fie 50-60 of weird agues and things. But it was dragged down by massive child mortality, as well as other mid-life causes.
I think the more critical thing is how much excess resource a civilisation can generate so it can afford to support people who are paid to think, rather than grow food and clothe themselves
Most societies through history, almost everybody had to be growing the food or involved in clothing. And ofc, rearing the next generation.
