The meaning becomes much clearer if a third type of society is included: the agrarian (peasant) societies which have comprised almost the whole world through almost all of recorded history. Then the link between child rearing practices and is apprent.

I wrote (in 2000):

“…Ancestral hunter gatherers experienced a way of life that was — in world historical terms — leisured and egalitarian, and enjoyed health and life expectancy at a high level. Of the three kinds of society as described by Gellner: hunter-gatherer, agrarian, and mercantile, it is probable that hunter-gatherers had the best life, overall. Hunter gatherer societies are the happiest and peasant societies are the most miserable — while industrial-mercantile societies such as our own lie somewhere in between.

“That, at any rate, is the conclusion of anthropologist Jerome Barkow — and his opinion is widely confirmed by the reports of many independent anthropologists who have experienced the alternatives of foraging, agrarian and industrial society.

“The ‘naturalness’ of nomadic foraging is also shown by differences in the harshness of child rearing practices in different types of society. Child rearing involves varying elements of forcible training that are necessary to prepare children for their social role. Peasant societies typically employ extremely repressive forms of socialization, extreme discipline, restriction, and the use of child labour. Industrial mercantile societies (such as our own) are much less tough on children — but still require many unnatural behaviors (eg. sitting in classrooms or examination halls for long periods of time without speaking or moving). ”

But nomadic foragers are able and willing to give their children even more freedom than the most liberal ‘modern parent’ — and such a relaxed upbringing of unstructured interaction with peers apparently prepares the child properly for the adult life to come.”

But another factor is probably important — and I was unaware of this in 2000 — some groups of hunter-gatherers would be cognitively incapable of modern child rearing (whether modern methods were adaptive or not).