To see whether estrus (heat cycle) was really “lost” during human evolution (as researchers often claim), researchers in the Department of Psychology at the University of New Mexico examined ovulatory cycle effects on tip earnings by professional lap dancers working in gentlemen's clubs.
The researchers used ads and flyers to sign up 18 lap dancers from local clubs. Each woman was asked to log on to a Web site and report her work hours, tips, and when she was menstruating. Lap dancers generally work 5-hour shifts with 18 or so 3-minute performances per shift. They average about $14 per "dance"--all of which is called a "tip" because it is illegal to pay for sex in New Mexico.
Normally cycling participants earned about US$335 per 5-h shift during estrus, US$260 per shift during the luteal phase, and US$185 per shift during menstruation. By contrast, participants using contraceptive pills showed no estrous earnings peak.