Ladies of the Night
It is often joked that prostitution is the "oldest profession," and there's actually a great case to be made for that aphorism's veracity. The Bible is filled with mentions of concubines, Ancient Greece had female "companions," Japan had geishas, Medieval Europe had brothels, and our time has Pretty Woman. In fact, we're not even the only animals who have developed this little social quirk. Chimps trade food for hanky panky, Adelie penguins will have full-blown affairs if an outsider male brings them stones, and macaque bros who volunteer to groom the ladies get some lovin' in return. To sum up, [insert profane Tyrion Lannister quote]!