 The drifty gene hypothesis was presented as part of a presidential debate at the 2007 Obesity Society meeting in New Orleans, with the counter-arguments favouring the thrifty gene presented by British nutritionist Andrew Prentice.The main thrust of Prentice's argument against the drifty gene idea is that Speakman's critique of the thrifty gene hypothesis ignores the huge impact that famines have on fertility.It is argued by Prentice that famine may actually have only been a force driving evolution of thrifty genes for the past 15,000 years or so (since the invention of agriculture), but because famines exert effects on both survival and fertility the selection pressure may have been sufficient even over such a short timescale to generate a pressure for "thrifty" genes.