“…Two partners in a human chromosome pair…often line up next to one another in parallel array, look each other over, compare their respective DNA sequences, and then swap genetic information. One frequent result is that a gene sequence present on one chromosome will now replace the corresponding sequence carried by its partner. Before this information transfer, two distinct versions of a gene may have resided on the two paired chromosomes; afterward, one of these versions is lost, being replaced by a duplicated version of the gene originally present on the other chromosome. The result is two identical copies of a gene in a cell that previously carried two dissimilar versions.” (p. 75)

“Estrogen is a fully natural hormone, native to the body, yet it contributes to carcinogenesis in the breast and ovaries. In the breast, it drives the proliferation of cells lining the milk ducts during the menstrual cycle and pregnancy. The monthly multiplication of these mammary epithelial cells is followed by their die-off, this cycle repeating itself over and over in most women from menarche to menopause–generally between ages twelve and fifty.

“Many researchers trace the roots of breast cancer to these repeated bouts of estrogen-driven proliferation. The increased incidence of this disease in modern times seems connected to dramatically increased menstrual cycling. Due to greatly improved nutrition, menarche begins four or five years earlier in late-twentieth-century girls than it did in their great-grandmothers. In addition, reproductive practices have changed in Western society. Childbearing and breast feeding, both of which suppress menstrual cycling, are now postponed and, when they occur, encompass only a few years of adult life, unlike a century ago, when three decades of a woman’s life were often involved in cycles of birth and lactation.” (p. 60-61)