AFP: A top scientist Monday contradicted US government claims that most of the oil that flooded into the Gulf of Mexico from BP’s busted well has degraded, insisting that more than half remains. Much of the spilled oil was dispersed, evaporated or removed by burning and skimming, but the “remaining fraction — over 50 percent of the total discharge — is a highly durable material that resists further dissipation,” Oceanographer Ian MacDonald told a presidential panel looking into the …