Food for Thought

David, Abigail and Nabal. This is the story we discussed at last night's bible study. At the end of the passage Abigail became David's wife. However, David was already married to Saul's daughter Michael. I know that back in biblical times men often had more than one wife. So my question is when did it become the norm for men to have only one wife? Don't get me wrong, I love the idea of every man only having one wife. I'm glad that's how it is today. I am just curious.