There have been plenty of jokes about menopause, but a study claims that the reason it exist is so that mothers and daughters-in-law wouldn't feel competitive about childbearing.
Scientists studied birth and death rates unfettered by modern contraception or heath care from 1700 to 1900 and found that women had more grandchildren if they stopped having babies around the age of 50. It also found that grandmas who had kids later in life or around the same time as their daughters-in-law were way less likely to have healthy children that lived long enough to grow into adults.
Based on the findings, researchers believe that menopause occurs so that grandmothers could help raise their grandchildren and to reduce competition between women:
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.
There is a clear biological benefit to a woman cooperating with her daughter: the women share 50 per cent of the same genes so being in competition for food and other resources makes little sense. This is not the case for a mother-in-law and daughter-in-law: they are not related, so it is logical they should compete to maximise on their chances of spreading their genes.
While it may seem like a wacky theory, study co-author Dr Andy Russell from the University of Exeter's Centre for Ecology and Conservation points out the following:
"We are so used to the fact that all women will experience menopause, that we forget it is seriously bizarre. Evolutionary theory expects animals to reproduce throughout their lifespan, and this is exactly what happens in almost every animal known, including human men. So why are women so different? Our study shows for the first time that the answer could lie in the relationship between a mother-in-law and daughter-in-law."