Heterogametic Sex Hypothesis

In mammals, including humans, sex is generally determined by the X and Y chromosomes. If a baby has a pair of X chromosomes, she’s a girl. If the baby inherits an X chromosome and a Y chromosome, he’s a boy. In birds, however, the situation is reversed. Female birds have a pair of unlike sex chromosomes while males have the like pair. (In this sort of sex-determination system, scientists use the letters W and Z, and talk about a ZW pair for female birds and a ZZ pair for males.) The “...

 Hormones on the Brain

At school, boys are fidgety, difficult, inattentive, and slow to learn, compared to girls. Nineteen out of every twenty hyperactive children are boys. Four times as many boys as girls are dyslexic and learning disabled. "Education is almost a conspiracy against the aptitudes and inclinations of a schoolboy," wrote psychologist Dianne McGuiness, a sentiment to which almost every man with a memory of school will raise a hearty cry of assent. But another fact begins to emerge at school. Girls a...