Judith Harris in Prospect Magazine:
It wasn’t until the 1970s that behavioural geneticists worked out productive techniques for answering questions about nature vs nurture. None of these methods is perfect, but they each have different flaws. It is therefore noteworthy that they all produced essentially the same results. Two results, actually—one surprising, the other not.
The unsurprising result was that genes matter. About half the variation in the measured characteristic—the differences from one person to another—could be attributed to differences in their genes.
The surprising result had to do with the environment. The aspects of the environment that don’t seem to matter are all those that are shared by all the children who grow up in a given family—which includes most of the things the word “home” makes you think of. Whether the home is headed by one parent or two, whether the parents are happily married or constantly rowing, whether they believe in pushing their children to succeed or leaving them to find their own way in life, whether the home is filled with books or sports equipment, whether it is orderly or messy, a city flat or a farmhouse—the research shows, counterintuitively, that none of these things makes much difference.