I’m always told by women that I should be thankful I don’t have to go through menstrual cycles or menopause. I am thankful for that, but it doesn’t mean that I’m apathetic to the female’s plight. Neither is science as it seeks to understand the causes of both, especially menopause. Women may think that nature just hates them, but a new theory suggests that evolution may have played a role in its development.

A theory published today in Ecology Letters suggests that menopause was a development of evolution to prevent competition between in-laws. The study, performed by ecologists at the University of Turku in Finland looked at meticulous birth, death and marriage records that were kept by the Lutheran church between 1702 and 1908. The results may surprise you.

They found that children died more often when the mother-in-law and the daughter-in-law gave birth around the same time. How often? Survival rates for children of the mother-in-law dropped by 50 percent whereas survival rates for children of the daughter-in-law dropped by 66 percent. Strangely enough, survival rates weren’t affected when the two gave birth at the same time.

So what does this all mean? Menopause may have come about to ensure the survival of the species. They theorized that the women giving birth around the same time would lead to the two fighting over which child gets food and shelter. Among poorer families, this would most assuredly lead to one child being given up. It’s theorized that older women go through menopause earlier so they can focus on raising their grandchildren instead of their own.

They also said that their research might help prove the “Grandmother hypothesis.” The hypothesis states that women stay alive long after their reproductive years end so that they can care for the next generation. It’s a huge contrast to the animal kingdom where a wide variety of females in non-mammalian species die not long after giving birth.

Of course, this is just one theory out of many that hopes to explain menopause. It’s still one of the greater mysteries of the human body that’s still not fully understood. Scientists hope that they can one day fully understand the cause in case the need ever arises to reverse the effects.

[h/t: Nature]