>All useful hypothesis are, by definition, extra-ordinary. Not in the sense of that applies to that saying. In this context "extraordinary claim" means "claim

>All useful hypothesis are, by definition, extra-ordinary. Not in the sense of that applies to that saying. In this context "extraordinary claim" means "claim with a very low prior probability". The saying can be expressed more precisely as "in order to upgrade to the level of expectation a hypothesis with a very low prior probability, it is necessary to make an observation of very low probability generally, but high probability given that the hypothesis is true." In other words, it's essentially just Bayes' theorem. And by no means are very-low-prior hypotheses inherently more useful. Certainly they have more impact than higher-prior hypotheses if they are validated, but in general, a very low prior means that a hypothesis is not worth wasting time considering. In some cases, a hypothesis can be so extraordinary that it becomes practically impossible to verify by experiment. In this case, for example, the hypothesis is so unlikely that it is quite difficult to imagine an experiment (or set of experiments) whose outcome was so unlikely that it would actually make us expect that humans were descended from ape-pigs.