New track and field sex-testing requirements revive longtime controversy in women's sports

According World Athletics - the global governing body for track and field - the presence or absence of the SRY gene is a reliable proxy for determining biological sex. A new policy requiring that competitors in the female category undergo testing for the gene is being implemented ahead of the World Athletic Championships, starting tomorrow in Tokyo. Supporters say the new policy guarantees fairness. Critics say it's unethical and unscientific. This is part of a long history of sex-testing in elite women's sports. The World's Bianca Hillier reports.