Less genome redundancy? Men have a single copy of most X chromosome genes. So if any of them are defective and affect cognition, there is no backup. Women have

Less genome redundancy? Men have a single copy of most X chromosome genes. So if any of them are defective and affect cognition, there is no backup. Women have a second X chromosome, that reduces the impact of a defective gene there. Daltonism and hemophilia are less prevalent in women for this reason.