Why Does a Mother Have Sons or Daughters?

We tend to think of the animal reproductive process as being all about males competing for females; males dance, sing, fight, or build a nest, and females dutifully choose the winner. In reality, females invest much more energy into producing offspring than males do, because they are responsible for creating the egg or embryo. Sons and daughters need different amounts of resources and energy from their mothers. Because of this, many female animals can make strategic decisions about whether to have sons or daughters, based on their environment and their own body condition. By “choosing” whether to have sons or daughters, the mother can increase her chances of having grandchildren and thus passing on her own genes. Amazingly, many female animals are able to produce the sex that will serve their interests the most!