Contrary to what one might think, diversity is not limited to ethnicity. For instance, consider family members who share a common ethnicity, genetics, and geographic and cultural background. Each member has a unique approach to problem-solving. We actually observe more variation within ethnic groups than between them. Diversity is about different approaches to problem solving.
Yes. However, the indicators of the relationship between identity and diversity are much more complex and subtle than most people realize. For instance, diversity research has shown that where one stores one's ketchup can be an indicator for ethnicity. For instance, most caucasians will store ketchup in a refrigerator, though bottle labeling doesn't require it. Most people of color do not. We often learn behaviors from our identity group without even knowing it.
When the problem gets too difficult, an individual can't get us to an optimized state or a better solution. There's a complexity barrier, at which we need to start reaching out to diverse sources of information to collectively find a better solution.
Some of the work that Los Alamos has done in homeland security is an excellent example. Los Alamos has developed a major molecular dynamic simulation capability; we can simulate a billion atoms. Through interaction of different groups, we discovered that we can apply this capability to simulate a global epidemic. By applying the knowledge developed in one area to a completely different discipline, we were able to develop a completely new solution.
Simple systems that have already reached optimization for efficient operation may not benefit from diversity. For instance, almost any change in performing the work of an assembly line system will cause decreased performance or failure. An assembly line is an optimized system, but not necessarily complex. However, diversity might be beneficial in the early stages of system development to achieve optimized performance or in a system review to implement continual improvement.