Thanks for the sound post, which I promptly retweeted! :-) From the perspective of evolutionary studies on religion, I would suggest to include cultural variance in the discussion of human cultural and genetic transmission. Certain religious groups as i.e. the Amish or Haredi Jews managed to develop stronger fences preventing much transmission from the outside while enhancing biological and cultural transmission to large numbers of offspring. Religiously liberal or secular groups are usually "more open" and (on average) less fertile. Best wishes from Germany!