Comment by danteembermage

Suppose person A has nuturing parents as a child. Nurturing parents encourage study and hard work leading to higher IQ as an adult. Moreover, nurturing parents feed their children nutritious food and no matter how many cigarettes or calories I consume as an adult I still had good nutrition when my brain (and sperm) were developing. I don't think their experimental design precludes this, although looking at sperm health does have the advantage that it's less likely to be influenced by decisions as an adult.