I may be misremembering, but my recollection is that he talks about the stresses of the parents being passed on from birth. My other vague recollection is that studies exist which prove this phenomenon to be true. A third vague recollection is that his own mother was persecuted due to religion, giving his theories and his reason to pursue them some level of credibility.

My memory is not machine-like in its efficiency. I am open to correction. But I believe GP may not be fully stating the facts for their own reasons.