This is a serious question.
From an evolutionary standpoint, it might make sense for women to devote their cellular efforts to reproduction instead of developing an energy-hogging brain, Ward suggested. Females of plenty of other species make this compromise, so why not humans?
The answer is that human females with larger brains had a significant fitness advantage, probably due to the complexity of human social interaction.
Developing big brains must have helped women pass on their genes, she reasoned. One possible explanation is that these larger, more connected brains helped ancestral females navigate an increasingly social world, where gaining benefits from other humans is just as important to survival as traits that improve fitness more directly, such as a strong immune system.