African countries require less of an Asian-style 'green revolution' than a 'cultural revolution' involving ideas, attitudes and institutions. This must include, but not be limited to, a belief in science-based innovation. If United Nations secretary-general Kofi Annan had expected a simple answer when he asked scientists two years ago what they could do about the food crisis in Africa, he will have been disappointed when he received their reply last week. The implication behind the way that Annan's question was phrased - how can a 'green revolution' be achieved in Africa? - is that the solution might be found in a set of relatively straightforward scientific and technical innovations in plant breeding. But, as the scientists' response, which was presented to Annan at a ceremony at the UN headquarters in New York last Friday, makes clear, Africa is a different case.