h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I honestly think you can never have been in love if you think it's the same thing as lust. I completely agree with you that lust is a way of furthering reproduction, but true love is much more than just sexual drive. It's more like a knowing that there's one person that not only you would have fun "mating" with, but you would also stay with them long enough to raise the results of that mating--and actually enjoy each other while you're doing that! It's being assured that there is reason to this world, and that there is someone willing to help you find it when you can't by yourself. It's not a concrete, scientific thing, but how many of life's best things are?