How do you pick a major when you're interested in pursuing advanced study in an interdisciplinary field?
If you're planning on doing advanced study in a truly interdisciplinary field such as the ones that you've listed, I'd recommend to look for what programs exist at the graduate level, and what their "home" departments are. If they're consistently in one department, I would then plan to do a major in the "home" area, and at least a minor in the other discipline (presuming there are only two fields overlapping). If you're planning to stop with master's degrees, you might consider two master's, but only if they were both funded. If you plan to do a PhD, there's probably no need for two separate PhD's—instead, try to look for a program where you can take coursework in both areas and do a project that combines them.