If marriage's primary purpose is procreation, then why not polygamy?

I ask gay marriage questions on here occasionally and sometimes I'll be told that two guys or two girls can't make a baby and thus this somehow disproves my whole theory that we can change laws to make them more equal.





My question now is if procreation is the line we are drawing, shouldn't we encourage or legalize polygamy in order to improve repopulation?If marriage's primary purpose is procreation, then why not polygamy?
marriage = two consenting adults





so simple, even you can understand.If marriage's primary purpose is procreation, then why not polygamy?
1. We already have too big a population. We don't want more.





2. Polygamy actually causes fewer children to be born than monogamy. Five men with five wives have more intimate encounters at the right time of the month than one man with those 5 wives. Plus those other unmarried four guys are out there causing trouble.





3. The primary purpose of monogamy is to support a healthy economy and a strong free democratic country. It's working better than any polygamous place. A LOT better.
You make a valid point.





Elder couples that have no need to procreate have no right to marry if that is the purpose of marriage.
I'm not sure why polygamy is even illegal since there is nothing constitutional to make it a crime