What did Graff mean about evolution working against girls in Ender's Game?

Answer 1

Graff means that most girls in the space school have not passed the grueling tests because over evolution girls have created a reputation that makes them more feminine and weaker than boys. For example, on page 24 Graff says, "A few girls. They don't often pass the tests to get in."

Answer 2

In "Ender's Game," Graff believed that evolution worked against girls because they were typically more nurturing and compassionate, traits that could hinder their ability to be aggressive and competitive in the military training program. Graff thought that girls were less likely to succeed in the harsh and cutthroat environment of Battle School because they were less inclined towards violence and dominance.