Just like individuals groups have their history. It is part of their identity, formative of their values, and leads into the habits and expectations members of the group will exhibit.
When trying to merge two teams there is another element that comes into consideration. It’s how a group sees and experiences the other. As both groups kept apart in the past, they both developed a lot of ideas about the other group. Most often these differences are based on the way the groups see themselves and don’t feel recognized in the way the other group acts. It often leads to ideas of superiority or inferiority.
To be able to bring the groups together and enable them to coexist constructively, the groups need the space to share their history and describe what their values mean to them. It is by being able to explain one’s difference and make it heard that they can become visible to the other. It is a way to express how varied and rich their identity is.
Having stated their difference, the groups can start to think about who they are together.
If this step is missed, both groups will argue that their differences make it difficult or impossible to join the other. Commitment to a merger might be there, but the differences will remain identifiers of problems.
If human beings feel that they can’t bring their identity and their difference into a group, they’ll search for ways to remain apart. It’s a way to keep their identity safe from disruption.