An anonymous reader writes "So, he or she has cheated on you for the umpteenth time and their only excuse is: 'I just can't help it.' According to researchers at Binghamton University, they may be right. The propensity for infidelity could very well be in their DNA. In a first of its kind study, a team of investigators led by Justin Garcia, a SUNY Doctoral Diversity Fellow in the laboratory of evolutionary anthropology and health at Binghamton University, State University of New York, has taken a broad look at sexual behavior, matching choices with genes and has come up with a new theory on what makes humans 'tick' when it comes to sexual activity. The biggest culprit seems to be the dopamine receptor D4 polymorphism, or DRD4 gene. Already linked to sensation-seeking behavior such as alcohol use and gambling, DRD4 is known to influence the brain's chemistry and subsequently, an individual's behavior."