npr1:

The Bible had religious men who were polygamists. Yay, polygamy!

Nature is rife with examples of animals devouring their young! Yay for that!

What else ya got...

The bible such as it is also ignores lesbianism completely. So it is a gender specific prohibition on homosexuality biblically. So to be consistent you would think those who adhere to biblical validity as endorsers of lesbian marriage.
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BS, not specificly prohibiting something does not endorse it as a desireable social convention. It's ignored. Its not life threatening like male homosexuality. Generally speaking everybody is, or is potentialy, bisexual, probably because it's not life threatening, and it's common in polygamous marriages among the wives I'm told by a few mormon women I know, and has no impact on anything. Polygamy generally resulted from a shortage of males in ancient times, casualties of the hunt, accident, predators or rival tribes.. Men had their hands full taking care of business, feeding everybody and making enough children to keep the tribe alive. Men wanting to skip all that, not have wives and children....In Sparta, besides loseing citizen rights, and public humilation, gangs of bachelor girls would chase down, attack and persecute in various ways bachelor men over 30, and they were not allowed to defend themselves.

Marriage is all about family, not whom you like to masterbate with now and then. It's not even about romantic love, thats was just a hopefull extra.