I don't know if I've thought about this before or what, but now that you've said it, it seems obviously true. Not that mixing older and younger little monsters

I don't know if I've thought about this before or what, but now that you've said it, it seems obviously true. Not that mixing older and younger little monsters is necessarily a panacea (I bet it would be rocky if you started tomorrow). But strict stratification can't be optimal. Other point about cousin relationships: interaction typically happens in a context that includes other adults, another moderating influence. I think that also runs in favor of your point.