Hearts are the lifeforce of most living organisms. Love is not associated with the heart or the circulatory system, just with hormones and the brain. Besides, why would you mess around with flirting around and feelings of love, when mammals can just skip that and perform their disgusting mating rituals. Point is... .-.. --- ...- . / .. ... / -. --- - / -. . . -.. . -.. .-.-.- -Azreal Zavula, his notes on human biology.
On an unrelated note, Happy late Valentines Day! :D Also, thanks to @ra2008incredibox for the original project.