Medicine: Capsules, Aug. 30, 1976

> The vast majority of human beings have two sex chromosomes: women have two of the X type, which guarantees their femaleness; men have one X (from mother) and a Y (from father). The Y, a tiny, misshapen bit of genetic material, overpowers the X and determines maleness—but little else, although it is widely believed that masculinity includes aggressive tendencies. Nature sometimes slips the conceptus an extra Y to produce an XYY male, almost certain to be well above average height. Because a disproportionately high number of XYYs were found in penal institutions,...

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