[dragonwriter]

Or that it's a product of a Y-linked genetic trait.

Or that it's a product of the socio-environmental factors discussed, but other socio-environmental factors like cultural gender roles mitigate it to undetectable levels in the mother » child and parent » daughter cases.

[braveo]

Or the he previous comment about lifestyle is applicable but only manifests itself for fathers as a result of society only recently starting to transition to women being able to be breadwinners.