When sports talk goes from X's and O's to X's and Y's -- chromosomes -- the level of expertise falls off dramatically. Amid the furor of some screeching headlines ("She is a He!"), competitors' accusations and track officials' confirmation that they will subject women's world 800-meter champion Caster Semenya of South Africa to gender verification tests, most observers appear to be in over their heads regarding the complexities of sexual identity. Almost everything about the issue is fuzzy: Where to draw the biological line between male and female, exactly what standard is used by the track authorities in deeming a female ineligible to compete as a woman, precisely what tests answer such questions. The International Association of Athletics Federations (IAAF) has asked for reports that will take weeks to review -- from a gynecologist, an endocrinologist, a psychologist, a specialist in internal medicine and a gender expert. This is not just about levels of testosterone, chromosomes, external genitalia or possible genetic mutations, experts said. Ross Tucker, a University of Cape Town exercise physiologist, called it "maybe the most difficult ethical debate in sport. Ranging from issues of social acceptance, to the role of urology, to the blurred lines between genetic advantage and unequal competition, it's all there." At the heart of the dispute, of course, are suspicions of whether Semenya cheated, intentionally or not; whether she had an unfair edge. Only 18, she first caught the track world's attention in July when she won the African Junior Championships with a world-leading time in the 800 -- almost nine seconds faster than she had run a year ago. That startling improvement triggered an IAAF doping investigation, which subsequently found nothing amiss. When Semenya reduced that July personal best by more than a second -- to 1:55.45 -- at this week's world championship meet in Berlin, two of her beaten rivals publicly complained about her being allowed to compete with women. "Just look at her," demanded Russia's Mariya Savinova. Italy's Elisa Cusma told Italian reporters: "These kind of people should not run with us. For me, she's not a woman. She's a man." Back home in South Africa, a Sowetan tabloid ran a front-page photo of Semenya's birth certificate, clearly listing her as female, and her parents expressed outrage at questions about their daughter's gender. Leonard Cheune, president of Semenya's national track and field federation, called the sex accusations racist, voiced by "the same people who don't want the 2010 World Cup (scheduled for South Africa), the same people who bring black people down and the same people who refuse to believe that Africans can make it on the world stage." A Young Communist League in South Africa said the aspersions cast at Semenya represented "a mentality of conforming feminine outlook within the white race." The minefield of identifying and banning males attempting to compete as females has been tread before, with inconclusive results. Ewa Klobukowska, the 1964 Olympic 100-meter bronze medalist and member of Poland's gold-medal relay team, originally passed a so-called "visual verification" test but three years later failed one of the just-instituted, more elaborate gender tests; Poland's world relay record was then struck from the books. Spanish hurdler Maria Jose Martinez Patino failed a test that revealed she was born with a Y chromosome, but her eligibility eventually was restored. The Russian Press sisters, three-time Olympic shot put and discus champion Tamara and her sister Iryna, together set 26 world records but both disappeared from competition when sex tests were instituted at international events in the late 1960s. A more shocking revelation about an Olympic champion came in 1980, when 1932 sprint gold medalist Stella Walsh was shot dead during a 1980 robbery attempt that it was learned, as a result of her autopsy, that she had male sexual organs due to a condition known as "Mosaicism," in which there are both male and female chromosomes. By current rules, Walsh was a man. On Friday, Britain's Telegraph newspaper contacted Andreas Krieger, who won the 1986 European women's shot put title as Heidi Krieger. After years of being required by the East German sports machine to use steroids, Krieger underwent a sex-change operation following athletic retirement. "I feel pity for her," Krieger told the Telegraph. "But what is really absurd is that the discussion about whether she is a man or a woman is being carried out in such a public forum." As Tucker wrote on his blog, "The Science of Sport": "The problem exists in that we divide the population into two, and then somehow assume that each part is roughly equal, which is of course not true. Not all men are as strong as Reese Hoffa (the American 2007 world shot put champion) or as fast as Usain Bolt. Similarly, there is no basis for saying that all women are 'equal', either . . . "However, there comes a point at which a distinction must be made. And I am reminded that this distinction exists because of cheating by athletes, and because, before it was in place, people did try to buck the system."