In general, the humane tendency is to couple with only one person and to be faithful to one's only partner. So dating someone else is very poorly looked.
But there are in some parts of Africa, for example, people in whom having relationships with other people is normal, even if you are married. Is it normal for humans to have one partner and to have strong feelings (such as jealousy and anger) when the partner is interested in someone else or when they go elsewhere? or is it society and evolution that taught us to think like that?