In Sex Differences in Intelligence, Dr Richard Lynn refutes the belief that males and females are equally smart. He presents the findings of his extensive research showing that, on the contrary, the average intelligence of young girls is higher than that of young boys. It is only in school-age students that boys and girls have approximately the same intelligence, while in adults the average intelligence of men is four IQ points higher than that of women. Lynn supports his Developmental Theory with a review of well over a hundred studies conducted by himself and a host of other reputable scientists.

The book discusses the reasons for the higher average intelligence of men among adults. One of these is that men have a larger average brain size than women. He refutes the contention of some feminists that brain size has no relation to intelligence. He argues that men have evolved higher average intelligence than that of women because this enhances their ability, in competition with other men for territory or status, to obtain women and thus pass on their genes. Another evolutionary explanation for men having a higher IQ lies in sexual selection such that females normally prefer to accept males with high intelligence as mates because they view them as potentially better providers for themselves and their children.

This path-breaking book will revolutionise the understanding of sex differences in intelligence.