p70.
Ibid, pp 23–25 and 21–22. On the evidence for a change in menstrual cycles, Rachel Bayer writes, “While the reasons behind why women menstruate remain unclear, research shows that the number of menstrual cycles modern women experience differs greatly from the number experienced by pre-agricultural women. It is impossible to know with certainty the reproductive patterns that prevailed 10,000 years ago. However, it is likely that the reproductive patterns of Stone Age women are more closely related to those of current hunter-gatherer societies than to those of Western women.” (From “The Impact of Increased Menstruation Rates on Women’s Health and Reproductive Cancers”, 19 December 2001).