Then I have miscommunicated by not mentioning the visceral in preference to explaining the technical. Marriage and sex are wonderful, fantastic things. Lifelong commitment and sharing bodies intertwine with each other to make life, mah-vellous. I was just trying to explain that in the OT monogamy is never commanded, as the OP was wondering, and polygamy is never condemned. I was interpreting that as the direction of his question. Then I also added, though, that in NT times things changes, and the one man-one woman concept was brought home as an ideal.
To respond to your comment, however, in ancient times marriage often was an economical tool. Marriages were arranged and didn't have a whole lot to do with love, though marriage for love did certainly happen (like Jacob to Rachel and David to Bathsheba). But often marriage was part of an economic system involving the exchange of dowries, part of a political system involving treaties, and part of their survival involving children (and therefore workers to sustain life). Our modern notions of marriage for love are quite foreign to the ancient mindset, even though I'm pretty happy about it.