Men have been constantly culled en masse so they're selected for cooperation at war. Women only failed to individually reproduce if they weren't sexually attracted to the invaders that killed the men of her tribe. This has obvious consequences.
>women the desire to protect the child is the most powerful force Bullsh*t - women exhibit no more concern for their existing children than lionesses do when the circumstances are similar. Hence why so much abuse of children by *step* fathers - she traded up so doesn't care.