Stepfamilies are at a much higher risk of experiencing domestic violence than are traditional families. Conflict, neglect, abuse, and incest are more frequently found in stepfamilies than in those whose members are all biologically related to all the others. Feelings of guilt and rejection are also more common in stepfamilies.
Traditionally, abuse and conflict in stepfamilies have been explained by economic stress, low socioeconomic status and emotional instability. But recent research has shown that these are probably not the primary causes of stress in stepfamilies. Evolutionary psychologists claim that the root of the problem is genetic, that we are biologically driven to perpetuate ourselves and therefore naturally prefer children in whom we have a personal genetic investment. Unconsciously stepparents see stepchildren as obstacles to self-perpetuation.
Research by psychologists at a Canadian university found that the rate of infanticide is 60 times as high and sexual abuse is about 8 times as high in stepfamilies than it is in biologically related families.
The human mind can override any genetic determinism.
Families with adopted children have relatively low rates of abuse and violence, thus proving that it is not biological relationships that make a stable family.