Subject: how did sexual reproduction come about?

I understand how the first organisms came about and that they 
reproduced asexually.  How then could sexual reproduction arise 
when asexual reproduction is so efficient, less complex, and 
requires much less organization and energy?  The only reason I 
can think of is because sexual reproduction allows for more 
varience and therefore better adaption to the environment but 
even this answer doesn't fully explain the evolution behind the 
concept.  Why would organisms ever desire to exchange genetic 
material? I realize this is a difficult question but please try 
to help me understand.

Re: how did sexual reproduction come about?