The loss of a woman’s fertility at a certain age is now linked to a man’s preference for younger mates.  It’s the latest theory as to why women go into menopause.  Researchers at Hamilton’s McMaster University hypothesize that over tens of thousands of years, a lack of reproduction among older women has given rise to menopause as an unintended result of evolutionary natural selection.  Study co-author Rama Singh is an evolutionary biologist.  He says it’s a very simple theory and it demystifies menopause as a simple age-related disease.  The researchers used computer modelling and found that over time, competition among men of all ages for younger mates left older females with much less chance of reproducing.  Singh says these women would have had children when they were younger, between the ages of 15 to 30, based on the computer model.  Any genetic mutations that caused an end to fertility later in life would be passed down from generation to generation, he said.  And over time, an accumulation of such mutations harmful to female fertility ended up producing a menopausal period that became part of the overall human female genome, the hypothesis suggests.  The research is published in this week’s issue of the journal PLOS Computational Biology.