By Isobel Williams & Joe Smith Most of us have felt a yearning for someone at some point in our lives, a teenage sweetheart, our other halves, even a celebrity crush, but now researchers say there may be a biological reason behind our infatuation with certain people. Experts have said that the feeling of desire, which causes us to crave certain people more than others, has a biological signature behind it. Some people can leave a unique chemical imprint on our brain, which is what drives us to form and maintain close relationships, according to a new study on voles. It all comes down to dopami…