Menopause Evolved to Prevent Competition Between In-Laws, Study Suggests

I would think that part of the reason for menopause is the long time a child is dependent. It would not be useful to have a baby if you are not likely to live long enough to raise it.

http://www.sciencedaily.com/releases/2012/08/120822071545.htm

ScienceDaily (Aug. 23, 2012) — Menopause evolved, in part, to prevent competition between a mother and her new daughter-in-law, according to research published in the journal Ecology Letters.

The study -- by researchers from the University of Turku (Finland), University of Exeter, University of Sheffield and Stanford University (US) -- explains for the first time why the relationship women had with their daughter-in-laws could have played a key role.

The data showed that a grandmother having a baby later in life, and at the same time as her daughter-in-law, resulted in the newborns of each being 50 per cent less likely to survive to adulthood.

The analysis helps to solve one of nature's great mysteries: why female humans, unlike most other animals, stop reproducing so early in life.

It also adds weight to the theory that the menopause evolved to allow women to focus on their grandchildren. Traditionally, this role included providing food for the family and protecting young children from accidents and disease.

.....

A child born to families with a mother-in-law and daughter-in-law reproducing simultaneously was twice as likely to die before reaching the age of 15. However, this was not the case in the instances when a mother and daughter had babies at the same time. This suggests that related women breed cooperatively and unrelated women breed conflictually.

.....

Different theories have been put forward for the evolution of the menopause in humans, including the idea that it evolved to protect older women against the danger of dying during pregnancy or childbirth. However, under two per cent of the pre-industrial Finns in this study died in childbirth in their mid-40s, and such risks of dying in childbirth are similarly low in hunter-gatherers today.