This past weekend I picked up a book "What the Dog S.aw" by M.al.colm Gl.adwell and it has an interesting story about women's ovulation changes over the century. In the pre-industrial era women menstruated less than the modern women due to late onset of puberty and high number of child birth and breastfeeding. It indicates that on average over a life time preindsturial women ovulated 100 times compared to 400 times for women now. For an evolutionary point of view the book raises the effect of increased number of ovulation/menses on women's health. I though this was interesting.
Since I have a 23-25 day cycle and with no pregnancy to show for I am sure my number will be way over 400 times by the time menopause comes around :)