As an 18-year-old runner from a village in South Africa received her gold medal in Olympic Stadium on Thursday night, activity away from the track had put her at the center of an international dispute: doctors here and in her home country were examining test results to determine whether she has too many male characteristics to compete as a woman. The case of Caster Semenya, who has burst to prominence this season, touched off a debate over whether she should be allowed to keep her medal and, more broadly, how sports officials are supposed to discern the fuzzy biological line between male and female.

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