Relatedness is relative: How can I be 85% genetically similar to my mom, but only related to her by half?

First of all, no. I am not the lovechild of star-crossed siblings, or even cousins, or even second cousins.  This is a gee-whiz kind of pos...

altruismancestrycooperationgenes for behaviorHamilton's ruleholly dunsworthinclusive fitnesskin selectionrelatednessselfishnesssociobiology