The following extracted from an email from an actual geneticist:
“I can tell you that risk of your kid getting schizophrenia goes way up (by a factor of about 2.5) if you him raise in a big city: safest is rural. Get the hell into Dodge. I’ve similar numbers for male homosexuality. In both cases, it’s where the kid grows up, not where he ends up as an adult. How does this work? Nobody knows.”
In the determination of how an adult human gets to be what he is, says this guy, there is a region of the Utterly Unknown. Researchers of course all claim title to this no-man’s-land, and Judith Rich Harris, whose new book I had just finished reading when I started this thread, claims it for group socialization, since that’s her specialty. However (says the geneticist) we don’t really know.