egy, takes over the population (Nowak et al 2004, Taylor et al 2004, Imhof Sc Nowak 2006, Nowak 2006a, Traulsen et al 2006, Lessard Sc Ladret 2007, Bomze & Pawlowitsch 2008). In this new approach, the Nash equilibrium condition no longer implies evolutionary stability. There has also been much interest in studying evol