darwin

so i get the whole darwin evolution thing. what i have been pondering recently is sex. how does that work. if at first it was all asexual reproduction and then some mutant came along without the capability to reproduce asexually and needed a partner then ...
or if it had both capabilities where did its partner come from and what are the odds of finding them? and what evolutionary benefit is sex. seems like it is easier and better to just clone oneself. Don't get me wrong here, I love sex. It is great fun. If I didn't know better I would say it is divine. I am just having a hard time seeing how needing a partner to continue the species is a benefit. I understand the genetic mixing and improving the stock of a group through breeding, but where does it all start? What is the lowest order of living thing that sexually reproduces? And what is the lowest order that does it for fun? I would research this topic more completely myself but alas all searches for sex are blocked in KSA. An unfortunate fact of life.