Susanne Justesen presented her Ph.D research on the relation between innovation and diversity - not trying to document if it exists, but how!
One interesting point just for at start:
In groups with homogenious members diverse opinions will be neglected referring to the need of efficiency, and the members will very often make decisions based on personal opinions and preferences. Furthermore homogenious groups will be very introvert and not try to seek knowledge from outside.
Heterogenious groups will have more discussions and often also conflicts leading to hopefully better qualified decisions - that will be made on grounds of research or at least qualified arguments. Heterogenious groups will furthermore tend to seek more information from outside.
When do you participate in a group where you all agree just a little bit too much?
In more heterogenious groups