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> 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, studies beginning in the 1960s suggested that they may be prone to aggressive criminality. It has taken a decade and a large-scale study by twelve Danish and American experts to refine that simplistic theory. The researchers report in Science that they tracked down males born in Copenhagen during four years (1944-47) and chromosome-typed 4,139 who grew to 184 cm. (approximately 6 ft.) or more. The XYYs among them numbered 2.9 per 1,000 and included proportionately more who had been convicted of crimes than did the general population: 42%, as against 9.3%. But surprisingly few of the XYYs' offenses involved aggression. The research team's conclusions: the XYY abnormality is likely to lead to lower intelligence and perhaps to some lawbreaking, usually petty. But whatever the offenses, they do not appear to result from a simple excess of aggression.

> The fear of breast cancer among American women is understandably great. As the commonest cause of death among women, it kills 32,000 yearly in the U.S., and any report of increased risk raises the level of alarm. This happened last week when the New England Journal of Medicine published a report that women who take estrogen drugs after the menopause to replace natural hormones run a greater risk of breast cancer than others. The cautionary conclusion was based on a study of 1,891 Louisville women. Of those studied, 1,028 or slightly more than half, had had their ovaries removed. Overall, the doctors treating the women diagnosed 49 cases of breast cancer; only 39 would have been expected in the general population.

The authors, headed by Dr. Robert Hoover of the National Cancer Institute, conceded that the statistics must be examined with caution. But the general conclusion was clear: while the incidence of breast cancer changes imperceptibly if at all during the first few years on estrogen medication, it may rise sharply after ten years and it almost doubles after 15 years. But duration of treatment is not the only factor. The doses taken and the dosage schedule are also important. Harvard Gynecologist Robert Kistner reviewed the latest report judiciously. "Estrogen must be used selectively in postmenopausal women," he said. "Only patients with definite symptoms of estrogen deficiency should be given the medication, and then only in the lowest possible doses. The Louisville report does not indicate a cause-and-effect relationship. More definitive studies are needed." Unfortunately, those may take years.

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