Causes of Menopause

"Putting the Men in Menopause"

This article goes into three different theories as to why women experience menopause, making them non-reproductive half way through their lifespan. Generally women experience menopause during their late 40s. 
The first and most popular explanation is the grandmother hypothesis. Older females genetically contribute to future generations by helping raise their grandchildren rather than continuing to bear and raise children of their own. The other leading theory is the life-span artifact hypothesis. This suggests that menopause is the by-product of an increase in life expectancy. The life expectancy for women in the early 1900s was 50 years old as opposed to now it is closer to 80. This assumes that over time, only males have extended fertility coupled with increased longevity, possibly to father more children.
The main subject of this article is a newly developed theory that looks at changes in mating behavior as a cause of early menopause with respect to life span. The modern trend of older men mating with younger women causes female fertility to decline with age. A team of researchers created a computer simulation to model this development over a long period of time.
In my opinion, this is not a very well development hypothesis because it makes too many assumptions about human's behavioral patterns and the genesis of menopause. It is, however, an interesting article and worth reading.

http://www.the-scientist.com/?articles.view/articleNo/37153/title/Putting-the-Men-in-Menopause/