[emmett]

There are systematic environmental differences for different cultures as well. This isn't to say "people aren't different", but rather that until you've estimated environmental differences and gene-environment interactions you know almost nothing about the nature vs. nurture debate.

See http://cscs.umich.edu/~crshalizi/weblog/520.html for a great summary, including specifically questions about Jewish intelligence. I know it's a bit long, but I promise it's worth reading.