You've really never had an attractive member of the opposite sex show up and the girls/guys get all competitive? I'm wondering how that's possible, it happened multiple times a week - a day even - to me in high school and college. I guess always being in mixed groups meant it was always subtly in play.

5 dudes chilling is a different dynamic than 3 guys 2 girls. People who keep insisting it's about some weird need for men to be offensive don't seem to have ever observed basic gender dynamics.(not saying you are, other responders)