New evidence that individual differences in human sexual desire can be attributed to genetic variations has been revealed by an Israeli research group, who say the findings will have an impact on individuals' understanding of their own sexuality and how sexual disorders will be treated in the future. The study, which was published in an online edition of the journal Molecular Psychiatry, revealed, for the first time, that common variations in the sequence of DNA impact on sexual desire, arousal and function, and lead to differences and diversity of the human sexual phenotype. The research was headed by Prof. Richard Ebstein of the Hebrew University and of Herzog Memorial Hospital and Prof. Robert Belmaker of Ben-Gurion University of the Negev's psychiatry division. Little has been known regarding the biological basis for individual differences in normal, human sexual behavior. Most significant variations in the expression of human sexuality have been viewed to be the result of learned behavior or psychological problems. However, recent advances in molecular genetic studies of human behavior and personality, imaging studies of sexual arousal and performance and neuroendocrinological investigations suggest that individual variations in many aspects of human sexuality, similar to other human behavior, are likely to rest on a firm foundation in the neurosciences. In the study, researchers examined the DNA of 148 healthy Israeli university students and compared the results with responses to questionnaires asking for the students' descriptions of their sexual desire, arousal and sexual function. The results showed a correlation between variants in the D4 receptor gene - which is responsible for producing the dopamine receptor protein (DRD4) - and the students' self-assessments on sexuality. Some forms of variants in this gene were shown to reduce sexual desire, arousal and function, while other common variants had the opposite effect. The arousal variant is believed to be a relatively new mutation, estimated to appear in Homo sapiens 50,000 years ago at the time of humankind's great exodus from Africa. About 30 percent of many populations carry the heightened arousal mutation, while around 60% carry the depressant mutation. This progress in understanding the biological basis of human sexuality provides a new way of viewing variations in sexual norms, without passing moral judgment, the researchers wrote. The implications of the study's findings are far-reaching and represent a revolutionary change in the way society, and especially psychology, may come to regard this central element of human behavior, they also wrote. The researchers predicted that as a result of their work, and other advances in neuroscience focusing on sexual behavior, a conceptual change would result and new methods of therapy would be developed for treatment of sexual dysfunction. For example, the researchers noted that many variations, such as weak libido, may be quite normal and not necessarily a product of dysfunction. It is possible, therefore, that sexual "problems" will eventually be redefined and to a great extent seen as requiring treatment via genomics-based medicine rather than psychotherapy.