Pronoun problems

pronoun problems

The passage below is from ‘the Blank Slate’ by Steven Pinker.

http://evolbiol.ru/blankslate/blankslate.htm

Nonetheless, genetic variation certainly has implications for human nature. If there are many ways for a mind to vary genetically, the mind must have many genetically influenced parts and attributes that make the variation possible. Also, any modern conception of human nature that is rooted in biology (as opposed to traditional conceptions of human nature that are rooted in philosophy, religion, or common sense) must predict that the faculties making up human nature show quantitative variation, even if ?their fundamental design (how ?they work) is universal. Natural selection depends on genetic variation, and though ?it reduces that variation as ?it shapes organisms over the generations, ?it never uses ?it up completely.

In this passage I want to know what the underlined pronouns stand for. I want to show my answers first.

?their : the faculties
?they : the faculties
?it : Natural selection
?it : Natural selection
?it : Natural selection
?it : genetic variation

Am I right in all of these?
If not, can you tell me which is right and which is wrong?