Indigenous people living in the African rain-forest, for example, use a variety of behaviours which evolved over hundreds of thousands of years but which have been discarded in the modern world, Diamond says.
Diamond, a professor, added that "It would be impossible, illegal, or immoral to carry out rigorous controlled experiments on Western children, in order to test outcomes of different child-rearing methods."
"But a huge variety of different methods has in effect already been tested by natural experiments: different societies have been raising their children differently for a long time, and we can see the results," he concluded.
