it does mean that you wouldn't let a stranger in, because why woudl you share resources. i think what is happening is that the application of our instincts in modern times dosent always line up. if i were alive 27000 years ago, i woudl never let anyone come in and just out of good will share the provisions of the tribe. there is a reason for that, and that reason is still carried by us. we haven't diluted those instincts. can i ask you why you never plan on having biological children? that seems very strange to me and i never understood why you never want to propagate your genes-unless you have one for self destruction. your nephews, as close as they are, they would never be as close genetically to your kids. also...how do you know which genes you want to pass on and that your nephews carry it?
one does not pass them on to have variety, the reason we have variety is a survival mechanism. we want to pass on the same, its a fight between the woman and the man to pass on as many of theirs dominant, recessive) as they can. so i want to pass on black hair, she wants to pass on red...etc etc this is a very large argument, with many moving parts and we can get caught up easily and drift- also, is the only reason dawkins not appeal to you is because he seems too sure of himself?