The statement, "extraordinary claims require extraordinary proof" is always helpful when people begin to babble about telepathy, UFOs, and other imaginary illusions. The human brain is exceedingly poor at discerning reality and we're ludicriously easy to convince. This is why abject nonsense has always been the currency of human discourse. Formerly, people believed in angels, ghouls, gods, goblins, and miracles. Today they believe in UFOs, aliens, paranormal babble, and other forms of modern-day superstition.
One of the curious results of the human inability to reason is that even when basic facts are known, almost no one is capable of applying them. For example, we know beyond any doubt that Darwinian evolution is essentially correct. We know that all life is in a constant struggle for survival and anything that even fractionally increases the odds of (temporary) survival will tend to spread across the species over time. We can therefore see that telepathy, for example, is an idle fantasy because - just like color vision - it would have spread through the gene pool had it ever existed. Some would be better telepaths than others, just as some people are taller, some are stronger, some are more intelligent, etc. But most people would already have some telepathic ability because its survival and reproductive value would be immense.
The fact that none of us can actually demonstrate telepathic powers under controlled conditions is sufficient evidence in itself to dismiss the idea. Only iron-clad repeatable demonstration of such ability would be sufficient cause for us to modify this conclusion. And such proof has never, ever, been presented - contrary to specious claims that are regularly made by charlatans and believed by the ignorant.
That said, because we humans are supremely gullible and for the most part utterly incapable of even rudimentary reasoning, superstitious beliefs will always retain their hold over those intellectually and emotionally incapable of moving beyond them. Thus we will continue to read about "mysterious signs" just as in ages past people babbled about "mysterious signs" such as comets, earthquakes, plagues, lost cats, ingrowing toenails, toothache, and indigestion.
