KnowHOW team explains: A difference in the infant mortality rates between boys and girls has been intriguing researchers for may years. The ‘biological advantages’ for girls, in comparison to boys, begin even before birth, and, like so many other differences between the sexes may be tied to hormones. For instance, a recent World Health Organisation (WHO) report says that more male foetuses are spontaneously aborted or stillborn.

The reasons need more investigation, but they seem to include sex differences in chromosomal structures and possibly a slower maturing of boys’ lungs because of the effects of the hormone testosterone. In most societies this pattern of excess male mortality continues for the first six months.

Girls’ inborn biological advantage may persist at least until menopause, because premenopausal hormones like oestrogen offer some protection from heart disease caused by damage that narrows blood vessels. The advantages may also include differences in susceptibilities and immunities to some disease-causing organisms. Still, some diseases are more likely to sicken and kill women.

However, the female potential for greater longevity than males, or the so-called biological advantage, hardly makes a difference in many cultures where infant girls have to survive malnutrition, neglect and even foeticide.

The question was sent by Suhas Sharma from New Delhi