Why do we have sex? It a question that has puzzled biologists for decades. The consensus is that sex is an evolutionary necessity to ensure survival. Yet the bdelloid rotifer has managed to abstain from the deed for over 40 million years. How has it survived? Quentin Coopertalks to biologist Professor Matthew Meselson of Harvard University, who believes he has solved one of science's biggest sex scandals. Producer John Watkins. E-MAIL: material.world@bbc.co.uk