I had assumed that all sexual-reproducing species were like humans but clearly not!

I kind of suspect this is related to something a former biologist once told me. Some aspects of biology are forgiving, some are not. If you look at the shape of human eyeballs, they're all pretty much the same, because if you mess with it too much, you lose functionality. If you look at the shape of human cartilage folds in the ear, you get more significant differences, because as long as there are some folds directing sound waves toward the earhole, the exact configuration doesn't matter as much. (The idea, I believe, is to get enough differences that our brain can learn to map the differences to distances.)

Sex differences strike me as the latter. You need some kind of difference between sexes, large enough that they can play complementary roles in reproduction, small enough that they're still members of the same species. There are many ways to get differences of that scope where both parties are still fertile. Therefore, you should expect to see different ways of doing it evolve.

I'm making this up, but it's reasoning backwards from things we know are true to principles I've learned.

Hee, yeah, the Fredersdorf fic was definitely my "light and easy" fic, lol. I think it helped that because of betaing your fic I had a lot of Opinions about Fritz and Fredersdorf and their characters :)

:D It also helped that we got some chatting going on with selenak!