The weight of evidence suggests, and indeed it is widely accepted, that physical performance phenotypes are highly polygenic (Rankinen et al., 2006; Spurway, 2006). Based on that suggestion and using clearly defined inclusion criteria, in our recent article (Williams & Folland, 2008) we showed that human genetic potential for endurance performance depends on polymorphisms of at least 23 loci and probably many more. We then developed the first genetic algorithm for endurance performance and used this to show that it is extremely unlikely that even a single individual in the world possesses what could be termed a ‘perfect’ polygenic profile for endurance. We concluded that world records should continue to advance, although probably at a steadily reducing rate, purely through an ever-increasing pool of participants that includes individuals with genetic profiles more advantageous for endurance performance.