In lectures on human development people are often surprised when I suggest that the menopause was what made us human. The vast majority of primates family structures are organised in harems, with a male who has twice the biomass of females expending huge amounts of energy fighting off other males to protect his group of females. In these social groups, females take care of offspring and can only mother one child at a time. Once she gives birth again, the old sibling is pushed into the world.
Once humans began to experience menopause, this changed the social order. It meant that females reproductive cycle ended. This, it is theorized, meant that they could spend more time supporting their children's children. Suddenly we could have more than one child at once and the length of childhood increased dramatically. Humans have the longest childhood in the animal kingdom. These ideas were largely based on anthropological and social biological studies. However, there is a new theory. Instead of having more children, a grandmother may pass on her genes more successfully by using her cognitive abilities to directly or indirectly aid her existing children and grandchildren. Such an advantage could have driven the evolution of menopause in humans. Using computational biology, Prof. Carla Aimé and colleagues at the Institute of Evolutionary Sciences of Montpellier developed computer simulations of human populations using artificial neural networks to test this idea. To read the results click here