Isn't this just a roundabout way of saying that people with lower IQs are more prone to criminal activity?
Neurological and Behavioral Consequences of Childhood Lead Exposure https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2689677/
>The underlying common pathway for all of these associations might be lead's adverse effects on executive functioning [19–21], resulting in poor impulse control.
Low impulse control in general seems to be one of the is the strongest predictors of criminal behaviour, whatever the cause.
sources:
http://journals.sagepub.com/doi/10.1177/0093854806292299
http://onlinelibrary.wiley.com/doi/10.1111/j.1745-9125.2000....
Look at people with Down-Syndrome, they are extremely thoughtful and nice. Least likely to commit a violent act or partake in criminal activity.
I'm reminded of the story about how an IQ researcher spotted the telltale signs of fetal alchohol syndrome before it was named, but had put it down to the bad genes of the native tribes he was studying. It seems when you'd decided that something in inherited, it's very easy to overlook environmental causes, even when they have very noticeable impacts.
Lead lowers IQ (and has other negative impacts). Fetal alchohol syndrome lowers IQ (and has other negative impacts). Adding Iodine to salt apparently raised average IQ by 15 points in areas where the natural diet was low in it.
Many things are apparently very inheritable, like height, yet in certain generations almost everyone is taller than their parents due to environmental factors. This isn't exactly rocket science.
My point was that in history, the people accused of being genetically inferior (the jews, the irish, the italians, native americans, africans, chinese etc.) have generally been outgroups that have been unfairly targeted by pseudo-science, not that IQ does not have a hereditary component.