I really like this article. It explores, among other things, the importance of adding new members to successful teams, in order to keep them successful.

"Northwestern University researchers discovered that the composition of a great team is the same whether you are working on Broadway or in economics.

The researchers studied data on Broadway musicals since 1877 as well as thousands of journal publications in four fields of science and found that successful teams had a diverse membership -- not of race and gender but of old blood and new. New team members clearly added creative spark and critical links to the experience of the entire industry. Unsuccessful teams were isolated from each other whereas the members of successful teams were interconnected, much like the Kevin Bacon game, across a giant cluster of artists or scientists."