And Wombat, psst… I really am a lousy engineer, because I’m a librarian by trade 
My fiance is a lousy engineer, because he’s a swimming teacher by trade. (Though he can repair bicycles and drill holes in the wall). Most people I know have not studied engineering.
Yeah, and I’m a lousy swimming teacher, too, but it’s not reasonable to infer that all Americans are lousy swimming teachers from that little fact.
As for the disease question, I’m hoping we haven’t chased all of the doctors out of this thread. Perhaps one will jump in. It is my understanding that certain groups of people (let’s say “genetic lines” instead of “races”) are more (or less) susceptible to various diseases. It’s not all environmental.
I, too, hope to a hear a doctor’s opinion about the genetic lines of people suspectible to certain diseases. I simply can’t see how “white caucasian” gives that information, but I stand to be corrected.