By contrast, men's sexual interest and output, usually measured by a reported number of orgasms per week, peaks in the teen years and then settles to a steady level (an average of three orgasms per week) for most of their lives. As I pointed out in March, most men remain sexually active into their 70s. According to the new study, as well as the study I wrote about in March, women's sexual ardor declines precipitously after menopause.
Why would women be more sexually active in their middle years than in their teens and 20s? Buss and his students say evolution has encouraged women to be more sexually active as their fertility begins to decline and as menopause approaches.
Here's how their theory works: Our female ancestors grew accustomed to watching many of their children — perhaps as many as half — die of various diseases, starvation, warfare and so on before being able to have kids of their own. This trauma left a psychological imprint to bear as many children as possible. Becoming pregnant is much easier for women and girls in their teens and early 20s — so much easier that they need not spend much time having sex.