Urban dictionary dot com defines friends with benefits as “two friends who have a sexual relationship without being emotionally involved.”
Let me introduce you to the deep limbic system.
The deep limbic system of your brain is the emotional center of you being. It, not your heart, is where your emotion is stored. This part of the brain also stores sexual memory. It gets tuned in to a splash of cologne, a great love song, and the physical act of sex. One of the nuerochemicals released during sex is dopamine. Dopamine makes you feel good; it creates a simultaneous sense of peace and pleasure. Anytime your body experiences pleasure—whether good or bad—the limbic system gets wash with this chemical, which causes you to crave more of what you just had. In essence, it creates addiction. Dopamine attaches you emotionally to the source of pleasure. Even if it’s “just a friend.” And there's more.
A chemical called "oxytocin" is also released during sexual expression ranging from intimate skin-to-skin contact to orgasm. This is a strong bonding chemical. An emotional glue. (Also present when a mother breast feeds her baby. Thus, bonding her to her new child.)
What I'm saying is that you get "addicted" and "bonded" to the people you have sex with. Like it or not. Believe it or not.
After twelve years of counseling sexually active teens, I’m certain that there is a chemical bond created between two people who have sex—whether you consider yourself just friends or you’ve been emotionally attached. There’s no way around it. Having sex bonds you to someone.
The Apostle Paul wrote, “Do you not now that he who unites himself with a prostitute is one with her in body? For it is said, ‘The two will become one flesh.’” Lauren Winner, author of Real Sex, says Paul is really saying, “Don’t you know that when you sleep with someone your body makes a promise whether you do or not?”
Friends with benefits?
It looks like—according to science—we were created to be monogamous!