Menopause partly evolved to prevent competition between mothers and their daughter-in-laws, researchers say. According to a study, when a grandmother had a baby later in life, and at the same time as her daughter-in-law, both newborns were 50% less likely to survive to adulthood.
The researchers, from the University of Sheffield and Turku University in Finland among others, said it could explain why women stop reproducing so early in life unlike most other animals.
It also adds weight to the theory that menopause evolved to allow women to focus on their grandchildren.
The researchers looked at information on birth and death rates from 1700 to 1900, before the advent of modern contraception or healthcare.
The study revealed that women had more grandchildren if they stopped reproducing around the age of 50.
The research team believes this was partly because of reduced competition.