Excuse the infidelity

"Our arboreal relatives, the monkeys, simply fled up into the high branches when danger threatened and, while feeding, all they had to confront was a fruit or a berry. But when our early ancestors came down to live on the ground, they had to give up scampering aloft to escape and also had to face dangerous competitors and prey when turning to meat-eating as a new way of life.

To become successful hunters required a new personality trait - bravery. If the primeval hunters were to survive as carnivores they had to be courageous and take serious risks. The females of the tribe were too important to expose to these dangers - their vital reproductive role ruled them out. But the males were expendable. If, inevitably, a few of them were killed, the others could easily maintain the reproductive rate of the still very small tribes. So it was the males who evolved into the pack-hunters who would become genetically programmed as risk-takers and whose job it was to bring home the bacon."

Hence, brilliant men always betray their wives. Not that I have too many pretensions of brilliance, but I hope the Girl doesn't think of this as a warning.