In my experience, teams that work best consist of members who a) have a lot in common in terms of upbringing, education, sense of humor(!) etc., and b) do not/a

In my experience, teams that work best consist of members who a) have a lot in common in terms of upbringing, education, sense of humor(!) etc., and b) do not/are not forced to compete among themselves too much, which correlates with a). It does help to have one or two outliers though.