South African runner Caster Semenya ran a perfect race to win the women's 800-meter world championship, said James Radice in Britain's Lets Talk More, but her fight for the gold medal isn't over. The International Federation of Athletics Federations is putting the 18-year-old through gender-verification tests. "It won’t be a pleasant experience for Semenya, but better to clear this up now than forever be suspected throughout what looks to be an illustrious career on the track." (watch Caster Semenya video: World Championship race)

Whether a runner is a man or a woman, said Erin Valois in Canada's National Post, is the sort of basic question South African athletics officials should have answered before a major competition. Caster Semenya's dramatic improvement over the last year -- along with her "muscular build and deep voice" -- certainly fueled enough speculation to justify looking into the matter. (watch Caster Semenya video: interview) But her "stunning rise from unknown teenage runner to the favorite in the 800 happened almost overnight," so there wasn't time to get answers before Semenya's stunning win.

The problem is that gender testing isn't as simple as it sounds, said Melonyce McAfee in Slate. "You can't tell for sure if an athlete is a man or a woman just by glancing at his or her genitalia. That's because some people are born with ambiguous sex organs, and others have a visible anatomy that doesn't match up with their sex chromosomes."

Determining whether Caster Semenya is eligible to race as a woman could take weeks, said Christopher Clarey in The New York Times. The testing begins with a visual evaluation by a physician, but also includes chromosome testing, gynecological investigation, X-rays, scans, and other tests. But sorting males from females can be more complicated than most people realize, said a Northwestern University bioethics professor, so in the end athletics officials may have to make a judgment call on what counts as male and female.