Diversity has multiple meanings which get conflated, Steve Sailer notes:
The first type of “diversity” is in settings where sheer talent matters most and the talent comes from all over the world. For example, the richest baseball team, the New York Yankees, has players from all over the world. For example, they just signed the best Japanese pitcher to a $22 million per year contract. Hiring people who don’t speak a common language doesn’t do much for clubhouse morale, but that’s probably overrated versus sheer individual skill in winning baseball games. The glamor of the diversity of the Yankees then sheds itself onto other, quite different uses of the term.
The second use of the terms “diversity” means to hire the less talented and less productive. For example, the Yankees very rarely hire Asian Indians or even Mexicans. And they sure don’t let any women on their team. But nobody notices and nobody cares. But if you mentioned the fact that women and, surprisingly, Mexicans aren’t really good enough to play much for the Yankees, people would get mad at you.
The third use is to refer to certain favored groups and to not refer to certain unfavored groups. For example, hiring a white NFL cornerback would, technically, increase diversity at that position, but nobody cares. Whites simply don’t count as diversity, even when they should.
The fourth use is to assume that diversity means that 1+1+1=4. If, say, the Yankees have some players who speak English, some who speak Spanish, and some who speak Japanese, they will play better as a team than if, all else being equal, they all spoke one language. Why? Due to the synergistical magic of diversity. This is the theme of many of the corporate image ads you see during the Olympics and golf tournaments.
Diversity as a virtue is from scholar circles. If you have ten Christians all from Norshire, they will all come up with the same ideas. You need one, maybe two. Having a German and a Chinaman instead of the spare eight is just good sense. In research, is team cohesion even useful?
“In research, is team cohesion even useful?”
Probably depends on how much the team actually has to work together, and there does have to be general agreement on the goals of the research itself, or even that scholarship itself is valuable. If you have one team member who thinks that the women on the team is an infidel whore, and another woman thinks that reality itself is a social construct, and another guy who thinks that relativity is “Jewish physics”…. well, that might be a bit too much diversity, which is why Universities are such a mess these days.