Although fewer females than males are born (the ratio is around 1:1.05), because of a longer life expectancy there are only 81 men aged 60 or over for every 100 women of the same age. Women typically have a longer life expectancy than men. This is due to a combination of factors: genetics (redundant and varied genes present on sex chromosomes in women); sociology (such as the fact that women are not expected in most modern nations to perform military service); health-impacting choices (such as suicide or the use of cigarettes, and alcohol); the presence of the female hormone estrogen, which has a cardioprotective effect in premenopausal women; and the effect of high levels of androgens in men. Out of the total human population in 2015, there were 101.8 men for every 100 women.
Women have, throughout history, made contributions to science, literature and art. One area where women have been permitted most access historically was that of obstetrics and gynecology (prior to the 18th century, caring for pregnant women in Europe was undertaken by women; from the mid 18th century onwards medical monitoring of pregnant women started to require rigorous formal education, to which women did not generally have access, therefore the practice was largely transferred to men).