Should one discipline one's children by smacking them? This question has long been debated without reaching agreement. We could settle it by a controlled manipulative experiment: we'd assign England's 47 counties at random to either of two sets: one set of 24 counties where parents are strictly forbidden to smack children; and another set of 23 where they are ordered to discipline kids by smacking. Thirty years later, psychologists could measure in which set of counties the resulting young adults are more creative, self-confident, law-abiding, prosperous, and happy.

Such a manipulative experiment would be considered impractical, illegal, and immoral. But a similar experiment has already been performed thousands of times, although not under such well-designed conditions. There are big differences in child-rearing practices among the world's thousands of human societies – especially among its traditional, small-scale tribal societies. Such societies still survive today beyond government control in New Guinea and the Amazon; and many traditional ways persist in rural areas of centrally governed nations.

Traditional societies are much more diverse than modern industrial or westernised societies. Some are more opposed to smacking their children, others are more committed to smacking than any westernised society. Traditional societies furnish natural experiments in child-rearing that have been running for millennia. By comparing the results of these natural experiments, we learn the effects of alternative child-rearing schemes that we would never test today by a manipulative experiment.

Familiar examples of such natural experiments are those used to identify effects of our diet and lifestyle on our health. For instance, why do most physicians believe that high salt intake tends to cause high blood pressure and strokes? Societies around the world vary 500-fold in their salt intake, from just 50 milligrams per day for Brazil's Yanomamo Indians to 27 grams per day in northern Japan, the world's stroke capital. The lowest-salt societies turn out to have the lowest blood pressures, while the highest-salt societies have high blood pressures. In this case it has been possible, legal and moral to use (gentle) manipulative experiments to confirm this conclusion: when volunteers consume a low-salt or high-salt diet for a week, their blood pressure respectively falls or rises.

As for natural experiments on smacking, most hunter/gatherer and small-farming societies don't smack their children. If one Aka pygmy parent hits an infant, the other parent views that as grounds for divorce. At the opposite extreme, small herding societies tend to beat their kids severely, because a negligent child who leaves a pasture gate open may let valuable livestock escape.

The small societies that don't smack their children differ on average from modern westernised societies in at least seven other features of child-rearing. They carry babies upright and facing forwards, so that babies see where they are being carried; they don't transport babies horizontally as in our prams, nor upright and facing backwards as in most of our chest-pouches. They respond almost instantly to an infant's crying; they don't let an infant cry for 10 minutes "to learn self-control". Responsibility for a group's children is shared not just by the parents but also among other adults of the group. Children from infancy onwards are given far more freedom of choice than western micromanaging parents permit. Infants are held almost constantly (whether by a parent, another adult, or an older child), and not left lying in a crib. Infants sleep on the same mat as their parents – probably no infant in human history was ever left to cry itself to sleep in its own crib or bedroom before 10,000 years ago. And mothers breastfeed children for several years.

How do the resulting children turn out? Many scientists have recorded their observations. I've also heard the views of many children of western parents who grew up in Africa or New Guinea (eg missionaries' children) and then returned to Europe or the US as teenagers. From both the scientists and the western children, I hear similar observations. Infants in traditional societies spend less time crying than do western infants. Traditional children's development of social skills is precocious by our standards. The words "curious", "self-confident", "emotionally secure", "creative", and "imaginative" keep cropping up in western accounts of traditional people. Compared to us, they spend far more time talking to and playing with each other face-to-face, far less time being passively "entertained" by watching something, and no time indirectly communicating by email, texting, or phone. Their teenage years aren't tormented by adolescent revolts and identity crises.

Those are qualities we admire, and that we'd like to see in our own kids. But we discourage our children by constantly telling them what to do, leaving them few choices, constantly grading and ranking them, hitting them, rationing our own time and contact with them, and leaving them alone and insecure for long times.

I'm not saying it would be easy for us to adopt all of those traditional child-rearing practices, even if we are convinced of their value. Some traditional practices may be difficult for many of us to reconcile with the demands of modern life, such as long-term breastfeeding. Other practices may be difficult for one set of parents to adopt if neighbouring parents are raising their children differently. But many traditional practices are easy for individual couples to adopt. You can carry your own infant vertically and facing forwards, regardless of how other parents transport their kids. Even if your neighbours smack their children, you don't have to smack yours.

By traditional standards, many of our modern child-rearing practices are weird. Traditional practices are the product of hundreds of thousands of years of natural experiments, by thousands of societies. If we choose, we can learn from all those natural experiments.