What provides the rules for the reproduction of new group members. anthro?

I believe it's group identity.
Group identity filled with several criterias that must be held by an individual to be considered as a member of social group.
For example, mensa could be considered as a social group. And in order to reproduce new group member, that individual shall have an iq of 150 and above.

Cultural norms have longed governed the rules of reproduction within an anthropological group. As times change so sometimes do these cultural norms. As time has progressed, political influence, expanding technologies, and socioeconomic conditions have effected changes within rules of reproduction among anthropological societies.

Because some African Americans were Caribbean like their ancestors