If men are from Mars and women are from Venus, it may explain at least one of their shared beliefs: Men and women can't be real friends. Many may point to the jealousy that plagues many rational people when a significant other befriends someone of the opposite sex. Boil it down to the inherent differences between the sexes. It just can't be done. Is it right? Wrong, say relationship experts. 'The belief that men and women can't be friends comes from another era in which women were at home and men were in the workplace, and the only way they could get together was for romance,' explains Linda Sapadin, Ph. [D], a psychologist in private practice in Valley Stream, New York. 'Now they work together and have sports interests together and socialize together.' This cultural shift is encouraging psychologists, sociologists and communications experts to put forth a new message: though it may be tricky, men and women can successfully become close friends. What's more, there are good reasons for them to do so. Society has long singled out romance as the prototypical male-female relationship because it spawns babies and keeps the life cycle going cross-sex friendship, as researchers call it, has been either ignored or trivialized. We have rules for how to act in romantic relationships (flirt, date, get married, have kids) and even same-sex friendships (boys relate by doing activities together, girls by talking and sharing). But there are so few platonic male-female friendships on display in our culture that we're at a loss even to define these relationships. A certain 1989 film starring Meg Ryan and Billy Crystal convinced a nation of moviegoers that romance always comes between men and women, making true friendship impossible. 'When Harry Met Sally set the potential for male-female friendship back about 25 years,' says Michael Monsour, Ph. D., assistant professor of communications at the University of Colorado at Denver and author of Women and Men as Friends: Relationships across the Life Span in the 21st Century. 'Almost every time you see a male-female friendship, it winds up turning into romance.' In 1989, Don O'Meara, Ph. D., a sociology professor at the University of Cincinnati-Raymond Walters College, published a landmark study in the journal Sex Roles on the top impediments to cross-sex friendship. Among several challenges he pointed out in his research, society may not be entirely ready for friendships between men and women that have no sexual subtext. People with close friends of the opposite sex are often barraged with nudging, winking and skepticism: 'Are you really just friends?' This is especially true, says O'Meara, of older adults, who grew up when men and women were off-limits to each other until marriage. What does the word 'befriends' (Line 3, Para. 1 ) most probably mean?