You keep talking about "biological differences between groups" over and over, but you never specify which groups you're talking about. The reason why is obvious.
MONOAMINE OXIDASE-A ENZYME, WHICH CATALYZES DEAMINATION OF DOPAMINE, SEROTONIN, ETC., WITH LARGE EFFECTS ON BEHAVIOR, IS MUCH MORE PREVALENT IN SOME GROUPS THAN OTHERS; THIS IS ONE OF THE MANY BIOLOGICAL AND BEHAVIORAL GROUP DIFFERENCES THAT MUST NOT BE DISCUSSED