if ideas were viruses, then, like any virus, they would mutate rapidly and often arbitrarily, with only the fitter ideas spreading and continuing their lineage. We simply do not see this with any sort of knowledge.
In the abstract, it might be tempting to imagine that irreducible complexity simply requires multiple simultaneous mutations - that evolution might be far chancier than we thought, but still possible. Such an appeal to brute luck can never be refuted... Luck is metaphysical speculation; scientific explanations invoke causes.
